SD
GND
VSENSE
CS
HV
VDD
DRV
UCC28630
1
2
3
4
8
6
5
EMC
Filter
to
VAC
VOUT
18
18.5
19
19.5
20
20.5
21
0 10 20 30 40 50 60 70
Output Voltage (V)
Output Power (W)
+5% Limit
115V/60 Hz
230V/50 Hz
±5% Limit
C001
1% Typical
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An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
SLUSBW3D MARCH 2014REVISED DECEMBER 2017
UCC2863x, High-Power Flyback Controller
with Primary-Side Regulation and Peak-Power Mode
1
1 Features
1 High-Power, Primary-Side CV/CC Regulation
Continuous Conduction Mode (CCM) and
Discontinuous Conduction Mode (DCM) Operation
Built-In 700-V Start-Up Current Source
Active X-Capacitor Discharge (UCC28630 and
UCC28633)
Adjustable Constant-Current (CC) Mode Limiting
(except for UCC28630)
High Gate Drive Current 1-A Source and 2-A Sink
Low Power Modes for <30-mW System Standby
Best-In-Class Light Load (10%) Efficiency >85%
PSR design with no opto-coupler - can meet high
CM isolation & surge requirements
VDD OVP for independent indirect output OV
under open-feedback fault conditions
Peak-Power Mode for Transient Overload
Shutdown Pin Interface for External NTC
Protections: Overvoltage, Overcurrent, Over-
Temperature, Overload Timer (UCC28630), AC
Line UV, Brownout and Pin Protections
Frequency Dither to Ease EMI Compliance
(except the UCC28632)
Create a Custom Design Using the UCC2863x
With the WEBENCH®Power Designer
2 Applications
AC-DC Adapters for Notebook, Game Consoles,
Printers
Open Frame SMPS for Industrial, Printer, White
Goods, LCD Monitors
Energy Efficient AC-DC Supplies for Nominal
Power 10-W to 65-W, (with up to 200% transient
peak power)
3 Description
The UCC2863x targets high-power, primary-side
regulated flyback converters. The ability to operate in
both CCM and DCM make the device suitable for
applications with a wide power range. The peak
power mode allows transient peak power delivery up
to 200% of nominal rating, with only a 25% peak
current increase, maximizing transformer utilization.
The transformer bias winding is used to sense output
voltage for regulation, and for low-loss input voltage
sensing. Advanced sampling techniques allow CCM
operation, and deliver excellent output voltage
regulation performance for opto-coupler-less designs
at power levels of 100 W and above.
A high-voltage current source enables fast and
efficient start-up. Advanced light-load modes are
deployed to reduce both controller and system power
consumption at no load and light load. These modes
enable potential system designs to meet 30-mW no-
load power for power designs up to 30 W nominal, 60
W peak.
The device has been designed for ease-of-use and
incorporates many features to enable a wide range of
designs. Extensive protection features are included to
simplify system design.
See the Device Comparison Table for details.
Device Information
PART NUMBER PACKAGE BODY SIZE
UCC28630
SOIC (7) 4.90 mm x 3.90 mm
UCC28631
UCC28632
UCC28633
UCC28634
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Simplified Schematic Typical Application Measured Regulation
2
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
SLUSBW3D MARCH 2014REVISED DECEMBER 2017
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Product Folder Links: UCC28630 UCC28631 UCC28632 UCC28633 UCC28634
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Table of Contents
1 Features.................................................................. 1
2 Applications ........................................................... 1
3 Description............................................................. 1
4 Revision History..................................................... 3
5 Device Comparison Table..................................... 5
6 Pin Configuration and Functions......................... 5
7 Specifications......................................................... 6
7.1 Absolute Maximum Ratings ...................................... 6
7.2 ESD Ratings.............................................................. 6
7.3 Recommended Operating Conditions....................... 6
7.4 Thermal Information (UCC28630, UCC28631)......... 7
7.5 Thermal Information (UCC28632, UCC28633,
(UCC28630, UCC28634)........................................... 7
7.6 Electrical Characteristics........................................... 8
7.7 Typical Characteristics............................................ 10
8 Detailed Description............................................ 13
8.1 Overview................................................................. 13
8.2 Functional Block Diagram....................................... 14
8.3 Feature Description................................................. 15
8.4 Device Functional Modes........................................ 52
9 Applications and Implementation ...................... 53
9.1 Application Information............................................ 53
9.2 Typical Application ................................................. 53
9.3 Dos and Don'ts........................................................ 73
10 Power Supply Recommendations ..................... 73
11 Layout................................................................... 74
11.1 Layout Guidelines ................................................. 74
11.2 Layout Example .................................................... 75
12 Device and Documentation Support................. 76
12.1 Device Support...................................................... 76
12.2 Documentation Support ........................................ 76
12.3 Receiving Notification of Documentation Updates 76
12.4 Community Resources.......................................... 76
12.5 Trademarks........................................................... 77
12.6 Electrostatic Discharge Caution............................ 77
12.7 Glossary................................................................ 77
13 Mechanical, Packaging, and Orderable
Information........................................................... 77
3
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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4 Revision History
Changes from Revision C (March 2015) to Revision D Page
Added UCC28634 initial release. .......................................................................................................................................... 1
Deleted text "for 65-W Nominal Power Design"..................................................................................................................... 1
Added text "PSR design with no opto-coupler - can meet high CM isolation & surge requirements".................................... 1
Added text "VDD OVP for independent indirect output OV under open-feedback fault conditions" ..................................... 1
Added Webench links............................................................................................................................................................. 1
Added Device Comparison Table details............................................................................................................................... 1
Added UCC28634 to the Device Information Table. ............................................................................................................. 1
Added UCC28634 to the Device Comparison Table.............................................................................................................. 5
Added UCC28634 to Thermal Information ............................................................................................................................ 7
Added UCC28634 to Electrical Characteristics...................................................................................................................... 8
Added UCC28634 to Electrical Characteristics...................................................................................................................... 8
Changed picture to represent added UCC28634 ................................................................................................................ 10
Added UCC28634 ............................................................................................................................................................... 13
Added UCC28634 ............................................................................................................................................................... 15
Added UCC28634 ............................................................................................................................................................... 16
Changed to correct picture link ............................................................................................................................................ 19
Changed to fix equation typo ............................................................................................................................................... 21
Added UCC28634 ............................................................................................................................................................... 41
Changed to correct typo ...................................................................................................................................................... 41
Changed to correct typo, changed from 4.7 to 47 ............................................................................................................... 41
Added paragraph to clarify the fault protection. .................................................................................................................. 41
Added UCC28634 ............................................................................................................................................................... 42
Added text "For UCC28634, all pin-faults are non-latching." .............................................................................................. 43
Added UCC28634 to the table ............................................................................................................................................ 52
Changed equation to fix typo ............................................................................................................................................... 67
Changes from Revision B (March 2014) to Revision C Page
Changed "No" to "Yes" in Device Comparison Table for Part# UCC28633D, "ACTIVE-X CAPACITOR DISCHARGE"
column.................................................................................................................................................................................... 5
Changed "Handling Ratings" table to "ESD Ratings" table. Moved Storage Temperature and Lead Temperature to
Abs Max Ratings table. .......................................................................................................................................................... 6
Revised Figure 40 ............................................................................................................................................................... 47
Changes from Revision A (January 2014) to Revision B Page
Added parts UCC28631, UCC28632 and UCC28633 to the datasheet. ............................................................................... 1
Added Active X-Capacitor Discharge Function reference to the UCC28630 and UCC28633. ............................................. 1
Added Adjustable Constant-Current (CC) Mode Limiting bullet............................................................................................. 1
Added Overload Timer reference to the UCC28630 only....................................................................................................... 1
Added Frequency Dither to Ease EMI Compliance exception for the UCC28632................................................................. 1
Added UCC28631D, UCC28632D and UCC28633D to the Device Information Section....................................................... 1
Added Device Comparison Table........................................................................................................................................... 5
Added UCC28632 Frequency dither range exception. .......................................................................................................... 8
Added UCC28632 Dither repetition period exception. ........................................................................................................... 8
4
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Product Folder Links: UCC28630 UCC28631 UCC28632 UCC28633 UCC28634
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Added UCC28633 Wake-up level (rising) exception.............................................................................................................. 8
Added UCC28633 SD VWAKE(rise) vs. Temperature exception............................................................................................... 12
Added text to the, "The controller operates in either DCM and CCM..." paragraph. .......................................................... 13
Changed the "Supply the device bias power during latched fault mode" bullet................................................................... 15
Added UCC28630 and UCC28633 only exception to the "AC sense input for X-capacitor discharge detect" bullet. ......... 15
Changed HV Pin Connection diagram. ............................................................................................................................... 15
Added sentence, "In the UCC28631 and the UCC28632, the HV pin can connect to either the AC or DC side of the
bridge.".................................................................................................................................................................................. 16
Added VIN(avg) definition. ................................................................................................................................................... 16
Added (UCC28630 and UCC28633 only) to the Active X-Capacitor Discharge section...................................................... 19
Added UCC28633 to the Improved Performance with UCC28630 section.......................................................................... 20
Added UCC28631, UCC28632 and the UCC28633 IOUT(lim) adjustment note. .................................................................... 37
Added UCC28630 only note to the Primary-Side Overload Timer section. ......................................................................... 38
Added UCC28630 only note added to the Overload Timer Adjustment section. ................................................................ 40
Added CC-Mode IOUT(lim) Adjustment section. ...................................................................................................................... 41
Added UCC28631, UCC28632 and the UCC28633 to the Fault Sources and Associated Responses table. .................... 42
Added The fault response (latching or auto recovery) depends on the device variant, per Table 3. ................................. 44
Added The fault response (latching or recovery) depends on the device variant, per Table 3. ......................................... 44
Added UCC28633 exception to the External SD Pin Wake Input section. .......................................................................... 45
Added External Wake Input at VSENSE Pin (UCC28633 Only) section.............................................................................. 46
Added UCC28632 exception to the Frequency Dither For EMI section............................................................................... 51
Added External Wake Pulse Calculation at VSENSE Pin (UCC28633 Only) section.......................................................... 66
Changes from Original (January 2014) to Revision A Page
Changed marketing status from Product Preview to Production Data................................................................................... 1
HV
VDD
DRV
1
2
3
4
8
6
5
VSENSE
SD
CS
GND
5
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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5 Device Comparison Table
ORDER NUMBER
FEATURES
ACTIVE-X
CAPACITOR
DISCHARGE
OVERLOAD
TIMER ADJUSTABLE
CC LIMIT FREQUENCY
DITHER SECONDARY-
SIDE WAKE UP
UCC28630D Yes Yes No Yes SD Pin
UCC28631D No No Yes Yes SD Pin
UCC28632D No No Yes No SD Pin
UCC28633D Yes No Yes Yes VSENSE Pin
UCC28634D No No Yes Yes SD Pin
6 Pin Configuration and Functions
7-Pin SOIC
Package D
(Top View)
PIN Functions
PIN I/O DESCRIPTION
NAME NO.
CS 3 I Current sense input
DRV 5 O Output drive pin for the external flyback MOSFET
GND 4 G Ground reference connection for all signals
HV 8 P High-voltage connection to the internal high-voltage start-up current source
SD 2 I Latching fault shutdown input pin. May be connected to an external temperature sensor
VDD 6 P Bias supply input pin to the device. Decoupled with a 1-µF ceramic bypass capacitor,
connect directly across pins 6-4. Connect an additional hold-up capacitor charged from the
transformer auxiliary bias winding to this pin.
VSENSE 1 I Sense pin for the flyback transformer bias and sense winding for output feedback regulation,
output OVP, and input voltage sense/UV protection
6
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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(1) Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. Exposure to absolute-
maximum-rated conditions for extended periods may affect device reliability. These are stress ratings only and functional operation of
the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied. All voltages
are with respect to GND. These ratings apply over the junction operating temperature ranges unless otherwise noted.
7 Specifications
7.1 Absolute Maximum Ratings(1)
over operating junction temperature range (unless otherwise noted) MIN MAX UNIT
Start-up pin voltage HV 700
V
Bias supply voltage VDD 20
Current sense input
voltage CS –0.3 1.5
All other input pins VSENSE –0.3 VDD
SD –0.3 VDD
Operating junction temperature range, TJ–40 125 °CStorage temperature, Tstg -65 125
Lead temperature 260
(1) Electrostatic discharge (ESD) to measure device sensitivity and immunity to damage caused by assembly line electrostatic discharges
into the device.
(2) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Manufacturing with
less than 500-V HBM is possible with the necessary precautions. Pins listed as ±2000 V may actually have higher performance.
(3) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. Manufacturing with
less than 250-V CDM is possible with the necessary precautions. Pins listed as ±500 V may actually have higher performance.
7.2 ESD Ratings VALUE UNIT
V(ESD) Electrostatic discharge(1) Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(2) ±2000 V
Charged-device model (CDM), per JEDEC specification JESD22-
C101(3) ±500
7.3 Recommended Operating Conditions
over operating junction temperature range (unless otherwise noted) MIN NOM MAX UNIT
CS input 0 1.0 V
All other inputs (except HV, CS) 0 VDD
SD pin external capacitance 0 1 nF
RHV, external resistor on HV pin, see Figure 15 180 200 220 kΩ
RP, external pull-up resistor on VSENSE pin, see Figure 21 3.8 3.9 4.0
7
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
www.ti.com
SLUSBW3D MARCH 2014REVISED DECEMBER 2017
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(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
7.4 Thermal Information (UCC28630, UCC28631)
THERMAL METRIC(1) UCC28630 UCC28631
UNITD D
7 PINS 7 PINS
θJA Junction-to-ambient thermal resistance 128.5 128.5
°C/W
θJCtop Junction-to-case (top) thermal resistance 57.3 57.3
θJB Junction-to-board thermal resistance 83.4 83.4
ψJT Junction-to-top characterization parameter 12.3 12.3
ψJB Junction-to-board characterization parameter 82.1 82.1
(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
7.5 Thermal Information (UCC28632, UCC28633, (UCC28630, UCC28634)
THERMAL METRIC(1) UCC28632 UCC28633 UCC28634
UNITD D D
7 PINS 7 PINS 7 PINS
θJA Junction-to-ambient thermal resistance 128.5 128.5 128.5
°C/W
θJCtop Junction-to-case (top) thermal resistance 57.3 57.3 57.3
θJB Junction-to-board thermal resistance 83.4 83.4 83.4
ψJT Junction-to-top characterization parameter 12.3 12.3 12.3
ψJB Junction-to-board characterization parameter 82.1 82.1 82.1
8
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
SLUSBW3D MARCH 2014REVISED DECEMBER 2017
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(1) CLOAD = 700 pF included on DRV pin.
(2) The SD pin functions as an NTC input pin (with internal pull-up) during normal operation. The internal pull-up is clamped to 4 V. At start-
up, the external temperature sensor (NTC) must be cool enough that the SD pin pulls up above the VTRIP(rise) start level. After start-up, if
this pin is pulled below VTRIP(fall) level, this activates external over-temperature shut-down.
(3) During low power modes (when FSW < FSMP(max)), the internal SD pin pull-up is disabled, and the pin functions as a transient wake-up
input. In this case, if the pin is raised above VWAKE(rise) level, the device wakes from low power sleep mode (rather than waiting for the
scheduled timer-based wake). This is useful for applications that require a response to load transients from zero or near-zero load,
where a wake-up signal can be appropriately coupled to the SD pin from the secondary-side.
(4) A decoupling capacitor on the SD pin should not be required; if used, it must not exceed 1 nF.
7.6 Electrical Characteristics
over operating junction temperature range (unless otherwise noted) and VDD = 12 V
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
START-UP CURRENT SOURCE
IVDD0 VDD pin short-circuit charging
current VDD = 0.2 V, VHV = 100 V 0.6 0.9 1.2 mA
IVDD1 VDD pin final charging current VDD = 11.9 V, VHV = 100 V 1.1 4.0 7.6 mA
ILEAK HV current source leakage current VDD = 18 V, VHV = 100 V HV,
current source off, TA= 25°C 0.1 0.5 μA
SUPPLY VOLTAGE MONITORING
VDD(start) VDD start-up voltage VDD increasing 13.00 14.75 16.50 V
VDD(stop) VDD minimum operating voltage
after start-up VDD decreasing after start-up 7.3 8.0 8.5 V
VDD(hyst) VDD start VDD stop level 6.5 V
VDD(reset) VDD reset restart level 3.5 5.0 6.5 V
VDD(ovp) VDD over-voltage protection level
VDD increasing after start-up,
UCC28630, UCC28631, UCC28632,
UCC28633 16.5 17.5 18.3 V
VDD increasing after start-up,
UCC28634 only 14.0 14.85 15.55 V
IDD(run) Supply current during normal
operation VSENSE = 0.45 V, CS = 0 V See (1)
CLOAD = 700 pF on DRV 6.0 9.0 13.0 mA
IDD(sleep) Supply current during sleep mode,
between switching pulses VSENSE = 8.0 V, VCS = 1.0 V, light-
load mode at 200 Hz, TA= 25°C 90 110 μA
OSCILLATOR
fSW(max) Maximum switching frequency VSENSE = 0.45 V, VCS = 0 V 110 120 130 kHz
fSW(min) Minimum switching frequency VSENSE = 8.0 V, VCS = 1.0 V, light-
load mode 0.18 0.20 0.22 kHz
DMAX Maximum Duty Cycle VSENSE = 0.45 V, VCS = 0 V 70%
tON(min) Minimum On time VSENSE = 8.0 V, VCS = 1.0 V, light-
load mode 550 600 650 ns
fSW(dith) Frequency dither range Except UCC28632 ± 6.7%
tDITH Dither repetition period Except UCC28632 6.0 ms
SHUTDOWN (SD) PIN (EXTERNAL FAULT INPUT)(2)
IPULLUP Internal pull-up current source See (2),(3),(4) 185 210 235 µA
VTRIP(rise) Fault ok level (rising) See (2),(3),(4) , UCC28630,
UCC28631, UCC28632,UCC28633 3.2 3.5 3.8 V
See (2),(3),(4) , UCC28634 only 2.2 2.5 2.8 V
VTRIP(fall) Fault trip level (falling) See (2),(3),(4) 1.7 2.00 2.3 V
VTRIP(hyst) See (2),(3),(4) 1.5 V
VWAKE(rise) Wake-up level (rising) See (2),(3),(4)Except UCC28633 1.8 2.2 2.6 V
tWAKE Wake delay time Delay to first DRV pulse 10 µs
9
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Electrical Characteristics (continued)
over operating junction temperature range (unless otherwise noted) and VDD = 12 V
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
VSENSE Pin (MAGNETIC SENSE)
VOUT(ref) Internal output voltage sense
reference level Required positive voltage at
VSENSE pin during off-time (at
25°C) 7.425 7.500 7.575 V
tOUT(smp) Vsense sample delay for VOUT Measured w.r.t. DRV falling edge 1.7 µs
VOUT(ovp) Internal output voltage sense OVP
level Measured w.r.t. regulation level,
tracking 120%
CURRENT SENSE (CS) Pin
VCS(max) Peak CS pin voltage level At maximum modulator demand 800 mV
VCS(min) Peak CS pin voltage level At minimum modulator demand 172 mV
VSLOPE Slope compensation ramp 30 mV/µs
OVER TEMPERATURE PROTECTION
TEMPTRIP Thermal protection shutdown
temperature Default internal setting, latch-off
protection 125 °C
TEMPHYST Thermal protection hysteresis 10 °C
GATE DRIVE OUTPUT (DRV)
ROH High level source resistance IOH = 100 mA 22 35 Ω
ROL Low level sink resistance IOL = –100 mA 1.2 2.5 Ω
7.7
7.75
7.8
7.85
7.9
7.95
8
8.05
8.1
8.15
8.2
±50 0 50 100 150
Voltage (V)
Temperature (ƒC)
C006
7
7.5
8
8.5
9
9.5
10
10.5
11
11.5
12
±50 0 50 100 150
Current (mA)
Temperature (ƒC)
C004
14.6
14.65
14.7
14.75
14.8
14.85
14.9
±50 0 50 100 150
Voltage (V)
Temperature (ƒC)
C005
0.95
0.955
0.96
0.965
0.97
0.975
0.98
0.985
0.99
0.995
1
±50 0 50 100 150
Current (mA)
Temperature (ƒC)
C002
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4
±50 0 50 100 150
Current (mA)
Temperature (ƒC)
C003
10
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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7.7 Typical Characteristics
Figure 1. IVDD0 Charging Current vs. Temperature Figure 2. IVDD1 Charging Current vs. Temperature
Figure 3. IDD(run) Current vs. Temperature Figure 4. VDD(start) Threshold vs. Temperature
Figure 5. VDD(stop) Threshold vs. Temperature Figure 6. Normalized VDD(ovp) Threshold vs. Temperature
0.98
0.985
0.99
0.995
1
1.005
1.01
1.015
1.02
±50 0 50 100 150
DRV Measure Gain (Normalized) (dB)
Temperature (ƒC)
C012
207
208
209
210
211
212
±50 0 50 100 150
Current (A)
Temperature (ƒC)
C013
115
116
117
118
119
120
121
122
±50 0 50 100 150
Frequency (kHz)
Temperature (ƒC)
C010
195
196
197
198
199
200
201
202
203
204
205
±50 0 50 100 150
Frequency (Hz)
Temperature (ƒC)
C011
4.5
4.55
4.6
4.65
4.7
4.75
4.8
4.85
4.9
4.95
5
±50 0 50 100 150
Voltage (V)
Temperature (ƒC)
C008
7.4
7.42
7.44
7.46
7.48
7.5
7.52
7.54
7.56
7.58
7.6
±50 0 50 100 150
Voltage (V)
Temperature (ƒC)
C009
11
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Typical Characteristics (continued)
Figure 7. VDD(reset) Threshold vs. Temperature Figure 8. VOUT(ref) vs. Temperature
Figure 9. FSW(max) vs. Temperature Figure 10. FSW(min) vs. Temperature
Figure 11. DRV Programming Current Measure vs.
Temperature Figure 12. SD Pull-Up vs. Temperature
1.9
1.92
1.94
1.96
1.98
2
2.02
2.04
±50 0 50 100 150
Voltage (V)
Temperature (ƒC)
C014
2.15
2.17
2.19
2.21
2.23
2.25
±50 0 50 100 150
Voltage (V)
Temperature (ƒC)
C015
12
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Typical Characteristics (continued)
Figure 13. SD VTRIP(fall) vs. Temperature Figure 14. SD VWAKE(rise) vs. Temperature
(except UCC28633)
13
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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8 Detailed Description
8.1 Overview
The UCC28630, UCC28631, UCC28633, UCC28633 and UCC28634 family of devices are highly-integrated,
primary-side-regulated (PSR) flyback controllers. The device supports magnetically-sensed output voltage
regulation via the transformer bias winding. This feature eliminates the need for a secondary-side reference,
error amplifier and opto-isolator. The device employs an advanced internal control algorithm that offers accurate
static output voltage regulation against line and load. The fixed-point, magnetic-sampling scheme allows
operation in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM). Additionally,
the device achieves accurate constant-current (CC) control of the output current limit using only primary-side,
current sensing. Uniquely, this CC function operates seamlessly as the operating mode changes between DCM
and CCM operation.
The controller includes an internal, high-voltage (HV) start-up current-source, and employs low-power sleep
modes and switching frequency reduction, to improve light-load efficiency and standby power. The device
typically achieves standby power levels between 0.05% and 0.1% of peak output power.
The controller operates in either DCM and CCM, using a mix of peak current-mode PWM (AM) and switching-
frequency modulation (FM) schemes. The control approach improves performance (efficiency, size and cost) and
can reduce transformer size and cost by allowing operation in CCM with FM during peak overload conditions.
Extensive protection features are incorporated, including output overvoltage protection (OVP), bias rail
overvoltage and undervoltage (OV/UV), active X-capacitor discharge, line undervoltage and brownout protection,
overcurrent overload timer, open- and short-circuit pin protections, peak current adjustment with line and
frequency dither for system EMI reduction. The various devices in the UCC2863x family offer a different mix of
features to suit a wide range of applications and requirements.
HV
VDD
DRV
VO Sample
VIN Sample
VREF Voltage Loop
Compensation
CV Demand
Isw
Sample
PIN Compute
PIN=(VIN x ISW(MID))x(tON/tSW)
VIN
ISW(mid) tON tSW
VO
PIN
PLIM
+
ILIM x VO
Current Loop
Compensation CC Demand
+
+
VREF x 120% OVP Fault
FM + AM
Modulator
Sleep Timer
+
tSW
IPK(dem)
IDD(LIMIT)
and
IHV(MEAS)
Fault Filtering and
Status Monitor
Start-Up and
Bias Control
PWM
Comparator
+
VTRIP(sd)
SD Fault
Q
S
R
IPK(dem)
SD Fault
OVP Fault
Overload Timer OCP Fault
OCP Fault
+
VTRIP(TEMP)
Internal
Temp
Sensor
Over-Temp Fault
tON(max)
tON(min)
tON
tSMP1
tSMP2
tSMP3
+
+
VDD
VVDD(ov)
VVDD(uv)
VDD OV Fault
VDD UV Fault
VDD OV Fault
VDD UV Fault
Over-Temp Fault
Timing and
Trigger
Generation
/
tON(max)
tON(min)
tSMP,n
n
X-Cap Fault
tSW
JFET Control
PWM Enable
PWM Enable
X-Cap Discharge
Detect
JFET Control
IHV(meas)
tSMP4
X-Cap Fault
tSW
tON
+
VAC(min) Line UV Fault Line UV Fault
Min
Demand
VO
4GND
3CS
2SD
1VSENSE
5
6
8
14
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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8.2 Functional Block Diagram
(a) AC-side (b) DC-side
SD
GND
VSENSE
CS
HV
VDD
DRV
UCC2863X
1
2
3
4
8
6
5
EMC
Filter
RHV
VAC
SD
GND
VSENSE
CS
HV
VDD
DRV
UCC2863X
1
2
3
4
8
6
5
EMC
Filter
RHV
VAC
15
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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8.3 Feature Description
The application designer requires some key device internal parameters in order to calculate the required power
stage components and values for a given design specification. Table 6 summarizes the key parameters.
8.3.1 High-Voltage Current Source Start-Up Operation
The controller includes a switched, high-voltage, current source on the HV pin to allow fast start-up, and
eliminates the static power dissipation in a conventional resistive start-up approach. This feature reduces standby
power consumption.
The HV pin has three major functions:
Supply the device start-up current
Supply the device bias power during latched fault mode
AC sense input for X-capacitor discharge detect (UCC28630 and UCC28633 only)
The UCC28630 and UCC28633 input supply to the HV start-up pin must be connected to the AC side of the
bridge rectifier as shown in Figure 15, in order to support X-capacitor discharge. More details are given in Active
X-Capacitor Discharge (UCC28630 and UCC28633 only), below. Connection to the AC side of the bridge also
allows faster detection of AC mains removal under latched fault conditions, allowing prompt reset of latched
faults for fast restart.
Figure 15. HV Pin Connection: (a) AC-side, (b) DC-side (UCC28631, UCC28632 and UCC28634 only)
V
IN(avg) = V
RMS × 2 × ¾2
N
tSTART = RHV × CVDD × lnFVIN:avg;
VIN:avg; F VDD:start_max;G
16
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Feature Description (continued)
In the UCC28631, UCC28632 and UCC28634, the HV pin can connect to either the AC or DC side of the bridge.
The addition of the 200-kΩexternal HV resistance (required for X-capacitor discharge sensing) limits the
available charging current for the external bias supply input capacitor. However, for typical values of between 22
µF and 33 µF of input capacitance, start-up bias times of less than 1.5 s are achievable at 90 VAC. Start-up time
can be estimated using Equation 1.
where
for AC connection and VIN(avg) = VRMS x2 for DC connection (1)
For 90 VAC, if CVDD = 22 µF and worst case VDD(start_max) = 16.5 V, then tSTART is 1.002 s.
Figure 16 illustrates the start-up behavior of the controller. The HV current source has built-in short-circuit
protection that limits the initial charge current out of the bias voltage pin until the bias voltage reaches VDD(sc).
This limits the power dissipated in the HV current source in the event of a short circuit on the VDD pin.
Thereafter, the HV current source switches to full available current. The controller remains in a low-power, start-
up mode until the bias voltage reaches VDD(start), after which the HV current source is turned off and the controller
initiates a start-up sequence.
VDD(start)
Rectified bias winding voltage increases with
soft-start, must exceed falling level on bias
capacitor before reaching VDD(stop) threshold
VDD(stop)
VDD charge current is limited for
VDD < 1.0 V (Short circuit protection)
Device Start Up
Soft Start
HV Current Source ON
Controller OFF Controller ON
Normal Operation
HV Current Source OFF
17
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Feature Description (continued)
The bias voltage decays during the start-up sequence at a rate dependent on the size of the energy storage
capacitor connected to the VDD pin. The VDD storage capacitor must be sized appropriately to ensure adequate
energy storage to supply both the controller bias power and MOSFET drive power during start-up, until the VDD
rail can be supplied through the transformer bias winding. If the bias voltage falls below VDD(stop) (due to bias
winding fault or an inadequate VDD storage capacitance), the controller stops switching, and transitions into low-
power mode for a time delay of tRESET(long), or until the bias voltage falls to the VDD(reset) level, whichever is
shorter. See VDD Capacitor Selection for required VDD capacitor sizing. Once the time delay elapses, the bias
voltage rapidly discharges to the VDD(reset) level, followed by turn-on of the internal HV current source, and a
normal restart attempt follows.
Figure 16. Normal Start-Up Sequence,
(assuming VAC > UV start threshold)
VAC rectified
VBULK
VDD
VDD(start)
VDD(stop)
VDD(reset)
DRV Terminal Line UV check
exploratory pulses Normal PWM
VAC(on) threshold
tONUV(max) at fSW(uv)
Line UV check
exploratory pulses
Apply AC
tRESET(short)
Normal PWM soft-
start
tONUV(max) at fSW(uv)
18
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Feature Description (continued)
8.3.2 AC Input UVLO / Brownout Protection
At start-up, once the VDD pin has reached the VDD(start) level, the internal start-up current source is turned off.
The controller tests the voltage across the bulk capacitor to determine if the level is high enough to allow the
power stage to start, if it has exceeded the rising ACON level. Because there is no load across the bulk capacitor
at this stage, the bulk voltage can be used as a proxy for the peak of the AC line. In order to measure the bulk
voltage in a low-loss fashion, the controller generates a sequence of three exploratory switching pulses at a
frequency of fSW(uv), at minimum peak-current demand level VCS(min) to avoid audible noise, and to deliver
minimum energy to the output of the power stage.
Based on the magnetic sampling information determined via the bias winding during these switching pulses, if
the output voltage is greater than the output overvoltage threshold, the pulsing stops immediately, and the
controller transitions into latched-fault mode. If, however, there is no overvoltage condition detected at the output,
the pulse-set completes. If the sensed line voltage is above the line ACON start threshold, then the controller
starts up normally, and begins to generate the PWM drive pulses that charge and regulate the output voltage.
Alternatively, if the sensed bulk level is below the ACON threshold, then the controller enters low power mode for
the reset period (tRESET(short)). It then depletes the VDD rail to the VDD(reset) level. At this point, the start-up
sequence repeats, and the device generates another set of exploratory switching pulses. This sequence repeats
indefinitely until the AC input is increased to a sufficient level that the bulk voltage exceeds the ACON level.
Figure 17. AC Input UVLO Detection and Start Up
Once started, the controller regularly monitors the bulk capacitor voltage. Because the ripple on the bulk
capacitor depends on the load level, the device determines the maximum bulk level every 11 ms (approprite for
minimum AC frequency of 47 Hz), so the AC peak can be determined. The controller provides input undervoltage
protection based on the sensed AC peak level. Once the peak drops below the ACOFF level for the delay period
(tUV(delay)), the PWM switching halts, and the controller enters low-power mode for the reset period (tRESET(short)).
The device then discharges the bias voltage to the VDD(reset) level, followed by a restart sequence. The controller
cycles through the ACON, monitoring (detailed above) indefinitely until the AC input again rises above the ACON
level.
0
50
100
150
200
250
300
350
400
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4
Vrms (V)
Time (s)
V_SELV
Xcap_90
Xcap_115
Xcap_230
Xcap_264
C016
P
X = V
AC
2 × CX
19
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Feature Description (continued)
8.3.3 Active X-Capacitor Discharge (UCC28630 and UCC28633 only)
Safety standards such as EN60950 require that any X-capacitors in EMC filters on the AC side of the bridge
rectifier quickly discharge to a safe level when AC is disconnected. This discharge requirement ensures that any
high-voltage level present at the pins of the AC plug does not present an electric shock hazard. The standards
require that the voltage across the X-capacitor decay with a maximum time constant of 1 second. Typically, this
requirement is achieved by including a resistive discharge element in parallel with the X-capacitor. However, this
resistance causes a continuous power dissipation that impacts the standby power performance. The power
dissipation in the discharge resistors depends on the X-capacitor value. Assuming that the discharge resistor
meets the 1-second time-constant requirement, (in other words, the R-C product is 1 second) the dissipation is
described in Equation 2.
(2)
Thus at 230 VAC, the discharge resistor causes 5.3-mW dissipation for every 100 nF of X-capacitance for a
typical 470-nF X-capacitor value, that causes 25 mW to be lost in the discharge resistors.
The safety standard does not mandate that the X-capacitor is fully discharged to zero within one second. It
simply requires the discharge rate to exhibit a 1-s time constant. Figure 18 shows the discharge characteristic
(for a 1-s discharge time constant) versus time, for disconnection at the peak of 90 VAC, 115 VAC, 230 VAC and
264 VAC. For AC inputs above 115 VAC, with 1-s discharge time constant, the voltage does not drop below the
Safety-Extra-Low-Voltage (SELV) 60-V level until 1 s or longer. In fact, at 264 VAC, 1.83 seconds elapse before
reaching 60 V.
Figure 18. X-Capacitor Discharge with 1-s Time Constant, for Various Voltages
CBULK Q
2lP
NOM × P
LL%
Dp×tXCAP(dis)
kVAC(pk)2FVSELV2o
CVDD R330 nF × :48.15;= 15.9 JF
CVDD RCX×FV
AC :pk;FV
SELV
V
DD:start _min ;FV
DD:reset _max ;G= CX×l373 F60
13.0 F6.5p= CX× (48.15)
20
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Feature Description (continued)
8.3.3.1 Improved Performance with UCC28630 and UCC28633
In order to reduce standby power and eliminate the standing loss associated with the conventional discharge
resistors, the UCC28630 and the UCC28633 devices incorporate active X-capacitor discharge circuitry. This
circuit periodically monitors the voltage across the X-capacitor to detect any possible DC-condition (which would
indicate that AC mains disconnection has occurred), and then discharges the voltage across the X-capacitor
using the internal HV current source. The X-capacitor discharge function discharges the X-capacitor to the SELV
60-V level in 1 s (as long as the design considerations discussed in this section are followed).
The device internally monitors the current into the HV pin to determine if the voltage across the X-capacitor in the
EMI filter has a sufficient AC ripple component. If insufficient AC content is detected, then a DC condition is
internally flagged. This causes the controller to enter low-power mode for the reset period (tRESET(short)), followed
by bias voltage discharge to the reset level (VDD(reset)) , and then the start-up HV current source turns on again to
effectively discharge the X-capacitor by transferring charge to the VDD reservoir capacitor.
Because the device monitors the HV pin to detect a DC condition on the X-capacitor, the system cannot operate
with DC input to the HV pin. Instead, the HV pin must be connected to an AC source only. The device interprets
any DC input on the HV pin as DC across the X-capacitor, indicating an AC-disconnect event. This causes a
repeating cycle of start-up and shutdown. The device requires an external 200-kΩof resistance on the HV pin, to
limit the current to a level below the saturation point of the internal HV current source. This limit produces a HV
input current that is approximately proportional to AC line, so that the AC content can be sensed.
The size of the X-capacitor that can be discharged depends on the VDD energy storage capacitor. Assuming the
worst case, a maximum X-capacitor disconnect voltage could be at the peak of 264 VRMS, and assuming that it
should be discharged down to 60-V SELV level, the minimum allowed VDD capacitor can be sized based on the
worst case VDD(reset) and VDD(start) levels as described in Equation 3.
(3)
For example, for a 330-nF X-capacitor value, the required VDD capacitor is 15.9 µF, so a 22-µF capacitor
suffices. (4)
In order to reduce the power consumption from the high voltage AC line, the device pulses current into the HV
pin at a low frequency with very low duty-cycle. The HV current source on-time (tON(HV)) , repeats at intervals of
tSMP(HV). Moreover, the pulsing occurs in bursts, with a time delay between bursts. The sampling occurs in bursts
of 21, at intervals of tSMP(HV), with a wait time of tWAIT(HV) between bursts. This reduces the effective average duty-
cycle to a very low value (approximately 0.2%), and minimizes the overhead of X-capacitor sampling current and
device bias consumption overhead to approximately 2 mW of extra standby consumption at high-line 230 VAC.
The device enables the X-capacitor monitor in latched fault mode, and in light-load regions where the power level
is below PLL(%), as a percentage of the nominal rated level. Above the PLL(%) level, the X-capacitor monitor is
disabled. At this load level the bulk capacitor discharges at a rate that is sufficient to also discharge the X-
capacitor, which appears in parallel with the bulk capacitor once the bulk voltage drops far enough to forward
bias the bridge rectifier diodes. In this case ensure that the bulk capacitance value is not too large for the power
level desired, which in-turn ensures that the bulk capacitor discharge rate is fast enough to discharge the X-
capacitor to meet the 1-s discharge target. This can be calculated in Equation 5.
(5)
CBULK Q
2 × l:65 × 0.125;
0.87 p × 0.04
:2 × 652F602;LswvJF
2
SELV
2
OFF
delayUV
LL%NOM
BULK VAC2
t
PP
2
Cu
u
¸
¹
·
¨
©
§u
u
d
CBULK Q
2 × d:65 × 0.125;
0.87 h × 1
:3732F602;LsuzJF
21
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Feature Description (continued)
Assuming a worst case AC disconnect at the peak at 264 VRMS (373 VPK), and a requirement to discharge to
SELV level of 60 V in tXCAP(dis) of 1 s, for a PNOM of 65 W at 87% efficiency, this is calculated in Equation 6.
(6)
Once the bulk capacitance value is chosen, also ensure that when the bulk capacitor has been discharged down
to the line UV ACOFF threshold, that it continues to discharge to an acceptable level during the line UV
persistence delay time (tUV(delay)) as shown in Equation 7.
(7)
Again, taking the example above:
(8)
Once the first constraint is satisfied, the second one is also automatically met.
Figure 19. X-Capacitor Discharge Activation, at 230 VAC, No Load
(red = X-capacitor, blue = bulk-capacitor, both 100 V/div)
22
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Feature Description (continued)
Figure 20. X-Capacitor Decay Rate Without Active Discharge
(time constant dominated by 20-MΩprobe impedance)
(red = X-capacitor, blue = bulk-capacitor, both 100 V/div)
GND RA
RB
VSENSE = VO x K1
NB
VO x K1
VIN x (NB/NP)
VO x (NB/NS)
NB
RB
RARP
VF
DRV
5
1VSENSE
23
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Feature Description (continued)
8.3.4 Magnetic Input and Output Voltage Sensing
A sense winding on the transformer is used to measure the input voltage and output voltage of the power stage.
This winding is typically the converter bias winding. The sense winding should be interfaced to the VSENSE pin
as shown in Figure 21. This interface requires that the voltage across the winding be scaled with a resistor
divider RA/ RB, and then offset with a switched, pull-up resistor RP(in series with a diode) connected to the gate
drive pin DRV.
Figure 21. VSENSE Pin Interface Arrangement
During the off-time portion of the switching cycle (also referred to as the flyback interval), the resistor divider (RB/
(RA+ RB)) scales the positive voltage swing at the VSENSE pin for output voltage regulation, as shown in
Figure 22. During this interval, since the DRV output is low, the diode in series with RPis reverse-biased, and so
RPis out-of-circuit.
Figure 22. VOUT Sense Using the Positive Swing on the Sense Winding
NB
BAV70
SD
GND
VSENSE
CS
HV
VDD
DRV
UCC28630
1
2
3
4
8
6
5
RP
100
RA
RB
GND RA
RB
VVSENSE = VDRV ± VF ± VIN x K2
NB
VIN x (NB/NP)
VO x (NB/NS)RP
VF
VDRV ± VF ± VIN x K2
DRV
5
24
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Feature Description (continued)
During the on-time portion of the switching cycle, when the DRV pin goes high (should swing very close to the
value at the VDD pin), the switched pull-up RPallows the negative swing on the winding to be level-shifted
positive, and thus also be sensed at the VSENSE pin, as shown in Figure 23. In this way the bias winding may
be used to sense both line input voltage and output voltage.
NOTE
The input voltage sensed by the transformer bias winding is actually the voltage across
the bulk capacitor, not the AC input voltage, because the bulk capacitor voltage appears
across the primary winding when the flyback switch turns on
Uses of the sensed bulk and output voltages:
Input AC mains UVLO
Input brownout
Line-dependent peak-current adjustment
Accurate output-current regulation
Output-voltage regulation
Output over-voltage protection (OVP)
Figure 23. Line Input Sense by Offsetting the Negative Swing on the Sense Winding
In order to protect the VSENSE pin from excessive negative current in the event of a manufacturing fault (such
as an open circuit on RP), use a series limiting resistor and clamping diode on the VSENSE pin. Combine the
clamping diode and DRV pull-up diode into a single-package common-cathode diode to reduce the component
count of the system. This is illustrated in Figure 24.
Figure 24. VSENSE Pin Protection and Interface to Bias Winding
IPK(dem)
Gate turn-off delay
Current Sense
PWM Comparator
PWM drive
FET Gate
Bias Winding
VO sample
delay
Time
25
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Feature Description (continued)
The device continually adjusts the input voltage sample delay, measuring the sample half-way through the on-
time interval, to ensure the cleanest signal. The device uses same mid-point sample trigger when measuring the
main MOSFET switch current (ISW). Sampling MOSFET switch current in the middle of the on-time automatically
measures the average current during the on-time, ISW(on_avg), which is required for the current limit and overload
timer block.
The output voltage sample point is always time relative to the turn-off instant. Internally, the device uses the CS
pin to determine the cycle end, rather than the PWM falling edge on the DRV pin. The device bases this
determination on the instant that the MOSFET switch current drops below the demanded peak current level
(IPEAK ) at the peak current mode comparator. Some delay always occurs from the falling edge on DRV to the
point when the external power MOSFET turns off. This internal timing method ensures a more accurate measure
of ISW(on_avg), and also ensures that the output voltage sample point is not measured too early, before the leakage
ringing has subsided. The effect of the gate turn-off delay and the adjustment of the output voltage sample point
is illustrated in Figure 25.
Figure 25. VOUT Sample Adjust for External Gate Delay
DRV
VIN Sample
VO sample
VIN sample
delay VO sample
delay
Sense Winding
Primary Current
Secondary Current Time
26
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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Feature Description (continued)
The sampling of the input voltage and output voltage signals on the bias winding must be synchronized to the on-
time and off-time flyback intervals respectively, because the signals occur during only those intervals in the
switching cycle. Typical waveforms and timing are illustrated in Figure 26.
More conventional knee-point detection schemes, where the sample is measured at the end of the flyback
interval when the secondary-side current has decayed to zero, inherently always operate in discontinuous
conduction mode (DCM). However, the fixed sample-point scheme used on the UCC2863x has the advantages
of being able to operate in regions of fixed frequency, and being able to operate in continuous conduction mode
(CCM). Fixed sample-point schemes conventionally suffer poorer regulation than knee-point schemes, because
there is always current flowing at the sample instant. This current produces a sensing error as a result of the
voltage drop produced across the secondary-side resistance and leakage inductance. This parasitic voltage drop
varies with output voltage, line and load, thus influencing the regulation. The UCC2863x devices uses a novel
internal compensation scheme to adjust for this parasitic voltage drop, and can deliver excellent static line and
load regulation, even when operating heavily in CCM.
Figure 26. VIN and VOUT Sample Trigger Timing
VO
RC(esr)
RSEC
VSEC
+
-
ISEC
+
+
+
+
-
-
-
-
+
-COUT
+
-
LLEAK(sec_bias)
VRECT
VLEAK
VR(sec)
VBIAS
ILOAD
VRC(esr)
VSEC = VOUT × l1FLLK(sec bias )
LSEC p + VRECT + ISEC × kRSEC + RC:esr;oFkILOAD × RC:esr;o
V
SEC = V
OUT + V
RECT + V
R(sec) FV
L:leak; + V
RC:esr;
27
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Feature Description (continued)
8.3.5 Fixed-Point Magnetic Sense Sampling Error Sources
To support operation in CCM, and allow operation at fixed frequency over a large percentage of the load range,
the UCC2863x uses fixed-point sampling rather than knee-point detection. When conventionally used, fixed-point
sampling typically suffers from poorer regulation performance. This poor performance results from the voltage
drops across the secondary-side parasitic resistance RSEC, and the secondary-side leakage inductance from
secondary-side to bias LLK(sec_bias), as a consequence of the fact that current remains flowing on the secondary-
side when the device measures the output voltage. As shown in Figure 27, the secondary-side pin voltage that
gets reflected to the bias winding is detailed in Equation 9.(9)
Equation 9 can be expanded and rearranged into Equation 10.
(10)
Figure 27. Secondary-Side Pin Voltage Contributors with Secondary-Side Current Flow
28
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Feature Description (continued)
Many elements contribute errors to the sensed secondary-side pin voltage, when measured across the bias
winding:
VL(leak):Negative voltage drop across the sec-bias leakage inductance LLK(sec_bias); assuming constant
regulated output voltage, this voltage drop is fixed constant offset, because VOUT/LSEC is constant as long as
the output is in regulation.
VRECT:Positive voltage drop across the output rectifier (assuming use of a conventional diode). This voltage
drop varies with load current and temperature. However, a constant nominal voltage drop can usually be
used, because the increasing forward voltage drop with increasing load current is largely cancelled by the
decrease in forward drop as a result of the temperature rise that results.
VR(sec):This is the drop across the secondary-side winding resistance. This value depends on loading, and
varies in proportion to the primary peak current demand that is set by the modulator.
VRC(esr):This is the drop across the output capacitor equivalent series resistance (esr). This value depends on
the difference between the secondary-side winding current and the DC load current being drawn.
Typically, the peak secondary-side winding current ISEC is many times larger than the load current, and the
secondary-side winding resistance is typically larger than the output capacitor esr. Thus, the last term in
Equation 10 involving ILOAD can typically be neglected.
The leakage inductance and secondary-side rectifier terms represent quasi-constant offset terms, so do not
affect regulation to a significant extent. Thus, the quasi-constant offset terms can be accounted for in the
calculation of the required scaling resistors to produce the desired setpoint voltage.
The remaining term that dominates the regulation error in Equation 10 is the drop across the secondary-side
winding resistance and capacitor esr at the sample instant, {ISEC x(RSEC + RC(esr))}. The controller internally
adjusts the control loop reference in proportion to the primary peak current demand in order to null the ISEC
related error term in the sampled bias winding voltage. Since the peak secondary-side current ISEC(pk) is the
primary peak current IPRI(pk) scaled by the transformer turns ratio, the internal control loop reference effectively
varies in approximate proportion to ISEC, resulting in dramatically improved regulation performance.
This improved regulation performance allows the use of primary-side regulation in a wider range of applications,
and at unprecedented power levels, operating in both CCM and DCM.
RA = RP × lNB
NPp × KLINE
NB
RARP
RB1
VF
RB2
DRV
5
1VSENSE
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Feature Description (continued)
8.3.6 Magnetic Sense Resistor Network Calculations
Because the device uses the VSENSE pin to measure both VOUT and VIN of the power stage, it is important to
calculate the resistor values correctly. The step-by-step design process is outlined in this section.
8.3.6.1 Step 1
Depending on the power level, choice of transformer size, and required trade-offs between primary MOSFET and
secondary-side rectifier ratings, the transformer turns NP, NSand NBwill be chosen first. The controller can
support a wide range of turns ratios.
Figure 28. Practical Magnetic Sense Setup with Extra Resistor RB2 for Setpoint Fine Adjust
8.3.6.2 Step 2
Once NP, and NBare known, the required value of RAin Figure 28 is calculated using Equation 11.
(11)
In this equation, the internal controller gain KLINE is 49.25 (see Table 6 for key internal controller parameters),
and the internal gains are designed for a fixed value for RP, (i.e. RPMUST be 3.9 kΩ).
10 k3ORTH < 20 k3
RTH =
RA × RB
RA + RB
RB = RA
LkV
OUT × k1F%LLK:sec _bias ;o + V
RECTo × @NB
NSA
V
OUT:ref ; F 1M
30
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Feature Description (continued)
8.3.6.3 Step 3
Once NS, target VOUT, output rectifier drop VRECT, and the secondary-side-to-bias leakage inductance LLK(sec_bias)
are known, the required value for RBcan be calculated. Referring to Equation 10, LLK(sec_bias) can be
approximated as a percentage of the secondary-side-referred magnetizing inductance LSEC. (See Magnetic
Sense Resistor Network Selection for details).
(12)
In this case, RBmay need to be empirically adjusted to achieve the required exact output set-point, especially if
VRECT varies or is not known precisely. For this reason, it is recommended that RBshould be implemented on the
system PCB as two parallel resistors RB1 and RB2 as shown in Figure 28, to allow easier fine-tuning of set-point.
For set-point tuning, only RBshould be adjusted. RAshould never be adjusted, because to do so would affect the
line sense gain and introduce errors into the line voltage measurement.
8.3.6.4 Step 4
Verify that the equivalent Thevenin resistance RTH of the RA/RBcombination falls in the required range of 10 kΩ
to 20 kΩ.
(13)
(14)
If the Thevenin resistance is outside of that range, then the original choice of turns ratio must be adjusted, and
design steps repeated until a valid value for RTH is determined. This is unlikely to occur in practice, unless an
extreme turns ratio is chosen. If RTH is outside this range, it triggers the VSENSE pin open or short pin-check at
start-up.
RCS
LPRI
Q1
VIN:pk _max ;
× VCS:min ;
tON:min ;
RCS
LPRI
QV
CS:min ;
tOUT:smp ;
× NS
NP
× 1
:V
OUT + V
RECT;
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Feature Description (continued)
8.3.7 Magnetic Sensing: Power Stage Design Constraints
Because the controller employs fixed-point sampling for output voltage sensing, there are some transformer
design constraints that must be observed. The minimum magnetizing volt-seconds during the on-time interval
occurs at the minimum CS pin voltage, VCS(min), under light-load conditions. This minimum should be the case at
all line voltages, because the controller compensates for line-dependent peak-current overshoot during turn-off
delay. The choice of transformer turns ratio, transformer inductance (LPRI), and current sense resistance (RCS)
must ensure that the corresponding reset volt-seconds during the flyback interval are sufficient that a valid output
sample is available at the sample point, tOUT(smp). This constraint is summarized in Equation 15.
where
VRECT is the voltage drop across the output rectifier (15)
Additionally, the device requires a minimum on-time, tON(min) , to ensure enough time for the system input voltage
(VIN) and switch current (ISW ) to be measured. To meet the minimum on-time requirement at maximum line, and
minimum load, the ratio of current sense resistance (RCS) to transformer inductance (LPRI) must meet the
constraint shown in Equation 16.
(16)
Equation 15 or Equation 16 sets the limit for the ratio of RCS to LPRI, but both need to be verified. See Typical
Application for more details.
VO Sample
VREF(adj)
Voltage Loop PID
Compensator
VO
tSMP
VSENSE
VREF KR(sec) IPK(dem)
+
++
-Error ekOutput ykTo fSW and
IPK(dem) Modulator
1
32
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Feature Description (continued)
8.3.8 Magnetic Sense Voltage Control Loop
Because the output voltage feedback is inherently a sampled signal obtained from the bias winding, the internal
voltage control loop is most naturally implemented digitally. The internal control loop implements the equivalent
of a PID loop in digital form. Because the output can be sampled only at certain intervals in each switching cycle,
the sample rate is naturally tied to the switching frequency, and the sample rate increases with increasing
frequency. However, the device clamps the sample rate at a normalized maximum rate, fSMP(max). But because
the device must always synchronize to the next available switching cycle to obtain a new sample of the output
voltage, the effective sample rate varies somewhat around this value.
The digital control loop compensator block diagram is shown in Figure 29. A new sample of output voltage is
supplied to the compensator at the normalized maximum clock rate (fSMP(max)),orfSW, whichever is lower. An
updated output voltage demand signal, yk, is produced at the same clock rate. This voltage loop demand
represents the required operating point on the modulator curves to keep the output voltage in regulation. The
modulator sets the appropriate switching frequency and peak current demand depending on the load power.
Figure 29. Digital Voltage Control Loop Simplified Block Diagram
The control loop PID gain factors are internally fixed values, optimized for flyback power stages in the range
between 20 W and 130 W. The loop is designed to work with magnetizing inductance values in the range
between 200 µH and 1500 µH. Assuming that the output capacitance value is chosen based on required ripple
current rating, then loop stability is not a problem. Adding extra output capacitance does not degrade the loop
performance and the resulting extra output hold-up improves transient response.
The Typical Application section includes gain-phase measurements taken using the 65-W UCC28630EVM-572
evaluation module.
SD
GND
VSENSE
CS
HV
VDD
DRV
UCC28630
1
2
3
4
8
6
5
CCS
RCS2
RCS1
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Feature Description (continued)
8.3.9 Peak Current Mode Control
The controller operates in peak current mode. The primary-side switch (MOSFET) current is sensed by a shunt
resistor (RCS1) connected in series with the source of the FET as shown in Figure 30. The voltage that is
developed across the sense resistor is connected to the CS pin of the controller. The device uses the current
sense signal at the CS pin to terminate the PWM pulse according to the peak current demand of the modulator.
The device automatically applies slope compensation as soon as the duty cycle of the DRV pin pulse exceeds
50%. This compensation provides stable operation up to maximum DRV duty cycle. The device applies this slope
compensation as a downslope on the demand signal at the PWM comparator, so is not measureable at the CS
pin. The device synchronizes the slope compensation signal to the PWM and is active only between 50% and
70% duty cycle, as shown in Figure 31.
Normal operating range for the CS pin is between 0 mV and 800 mV. The RCS1 resistor should be scaled such
that the peak current at maximum peak load and minimum bulk capacitor voltage produces a signal of
approximately 800 mV peak at the CS pin. This resistor value is calculated in conjunction with the calculation of
the required primary magnetizing inductance, as outlined in Notebook Adapter, 19.5 V, 65 W, section.
Figure 30. Primary-Side Current Sensing
Peak Current Demand
With Slope Compensation
PWM Clock at 60 kHz
100 mVPP
50% 70%
30 mV/s
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Feature Description (continued)
A nominal 100 ns of filtering that is internal to the CS pin helps filter the leading turn-on spike of current.
Depending on PCB layout, an RC filter (RCS2 and CCS) may be required on the CS pin as shown in Figure 30 to
filter noise and spikes. The capacitor CCS should be positioned as close as possible to pins 3 and 4 and tracked
directly to the pins. Series resistor RCS2 should also be located close to pin 3 to minimize noise pick-up. RCS2
value should not exceed 20 kΩ, because a larger value could be detected as a possible open circuit on the CS
pin during the start-up pin-fault checks. The R-C filter time constant should not be excessive (timing between 100
ns and 200 ns is typical). Otherwise the filter reduces the measured peak current, and allows greater actual peak
current to flow versus the modulator demand level. Such effects force the regulation loop to reduce the switching
frequency to compensate, and at highest line, no load, this can lead to regulation difficulties if the control loop
attempts to drop the frequency so far that it reaches the fMIN limit.
Figure 31. Peak Current Demand with Slope Compensating Downslope
KLINE:adj ; = FRCS
LPRI
× ktPROP:gate ; + tOFF:ext ;oG PstrJand < uwrJ
+
S Q
QR
LEBs
Filter
Frequency and
Peak Current
Modulator
IPK(dem) adjust
vs. VBULK
CS
VBULK
Gate
Driver
RG(on)
RG(off)
VBULK
LPRI
RCS1
RCS2
CCS
Low line High line
IPK(dem)
Propagation delay
IPK overshoot IPK overshoot
IPK(adj)
Propagation delay
DRV
5
3
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Feature Description (continued)
8.3.10 IPEAK Adjust vs. Line
The controller applies a line-dependent reduction in the peak-current demand to correct for the current overshoot
due to the PWM and gate drive propagation delay, with the aim of delivering a constant peak current versus line
at a given power level. This maintains approximately constant switching frequency versus line for a given power
level (until the operation enters into CCM), improves regulation, reduces audio noise, and allows lower standby
power at high line. If not corrected, the current overshoot could become significant at high line, where the
inductor current di/dt is higher. This overshoot would cause a pronounced increase in transferred power per
switching cycle at high line, because power is proportional to IPK2. The effect of the delay on the peak-current
overshoot is illustrated in Figure 32.
Figure 32. Peak-Current Demand Adjustment vs VBULK to Correct Prop Delay Overshoot
For different power stage designs, the combination of primary magnetizing inductance LPRI, current sense
resistance RCS and external MOSFET gate turn-off delay tOFF(ext), must be verified against Equation 17, to ensure
that the internal peak-current compensation gain range is satisfied. The KLINE(adj) factor should be within the
range indicated. If the external turn-off delay is too long, then the internal IPEAK adjustment factor is too low, and
the adjustment at high line is not able to achieve the required level of over-shoot compensation. As noted
previously, this could result in regulation difficulties at no-load, and may cause poor line and load regulation, or
require an increase in output pre-load power.
where
where tPROP(gate) is the internal controller gate-drive turn-off propagation delay, given in Table 6. (17)
VSENSE
VO Sample
VIN Sample PIN Compute
P=(VIN x ISW(MID))x(tON/tSW)
VIN
tON tSW
VO
PIN
PLIM
ILIM x VO
tSMP1
tSMP2
+
-
Current loop
PI compensator
Error
iek
Output iyk
CS ISW
Sample ISW(mid)
tSMP3
To fSW and
IPK(dem) Modulator
1
3
IOUT = VIN × IIN:avg ; × D
VOUT
= PIN:lim ; × D
VOUT
= IOUT:lim ;
P
IN = V
IN × IIN:avg ; = V
OUT × IOUT:lim ;
D = PIN:lim ;
36
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Feature Description (continued)
8.3.11 Primary-Side Constant-Current Limit (CC Mode)
In addition to the peak-current mode PWM function, the device also uses sensed current at the CS pin to
estimate the secondary-side load current. The device samples the CS pin voltage and measures it in the middle
of the on-time, which is effectively the average switch current during the on time, ISW(avg_on). This measurement
scheme is the case during both DCM and CCM operational modes. The average switch current during the on
time is scaled by the PWM duty cycle to give the IIN(avg) of the power stage. The power stage input power, PIN,
can then be estimated as the product of (VIN x IIN(avg)). The CC mode operation regulates PIN to track (IOUT(lim) x
VOUT), if PIN increases to reach PIN(lim), thereby achieving a regulated constant current as shown in Equation 18.
(18)
(19)
Figure 33. Digital Current Control Loop Simplified Block Diagram
IOUT:lim ;=
1
RCS1
×
NP
NS
×
KCC1
KCC2+V
OUT × NP
NS
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Feature Description (continued)
Assuming that the power stage efficiency does not change significantly with operating point, by regulating the
input power in inverse proportion to output voltage, this regulates output current. This achieves a brick-wall CC
characteristic, where the output current is regulated as the input voltage changes and as the output voltage rolls
off, regardless of power stage operating mode (CCM or DCM). The CC mode protection eliminates the
characteristic load current tail-out that is typically seen with peak-current mode control as output voltage
collapses and operation goes deeper into CCM mode.
NOTE
As the output voltage decreases in CC mode, the VDD level also decreases. If the
overload is severe, the drop in output voltage causes VDD to drop below the VDD(stop) UV
level. This drop causes a shutdown for tRESET(long), as given in Table 6, followed by a
restart attempt.
The constant-current mode output current limit level (IOUT(lim)) is a function of both the RCS1 resistor and the
transformer turns ratio. The device uses an internal reference and gain for the CC loop, KCC1 and KCC2, that set
the CC IOUT(lim) point as a function of the chosen turns ratio, output voltage and current sense resistance as
shown in Equation 20.
(20)
For the UCC28631, UCC28632 and the UCC28633 devices, the IOUT(lim) can be adjusted to be a percentage of
the maximum value calculated by equation Equation 20. see CC-Mode IOUT(lim) Adjustment for more details.
38
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Feature Description (continued)
8.3.12 Primary-Side Overload Timer (UCC28630 only)
The internal overload timer in the UCC28630 uses the same output load current measurement that is used by
the CC loop. This measurement tracks the power stage thermal stress, and protects the power stage against
output overload. If the output is overloaded for too long such that the power stage would be over-stressed, then
the PWM shuts down, and enters low-power mode for a time period of tRESET(long); thereafter the device
discharges VDD to the VDD(reset) level and initiates a hiccup mode restart.
The overload timer operates by taking an estimate of output current, squaring it (assuming the power stage
losses are dominated by resistive I2losses) to produce (K x I2OUT), where K is a scaling gain factor. The overload
timer is constantly running at every load level, and accumulates at a rate dependent on the difference between
(K x I2OUT) and the previous level of the timer. If (K x I2OUT) is greater than the previous timer level, the timer level
continues to increase; if (K x I2OUT) is less than the previous timer level, then the timer level decreases. At any
steady load, the overload timer level eventually settles at a level proportional to I2OUT. Because the overload
timer level adjusts at a rate dependent on the difference between (K xI2OUT) and the previous level, the timer
initially reacts faster to larger differences, but over time settles exponentially at a level proportional to (K x I2OUT).
As shown in Figure 34, in both the first and second examples, the initial steady load allows the timer to integrate
and settle at a level proportional to the load. The margin to the over-load trip level depends on the historical
loading, lower prior average loading results in greater future over-load capability, and vice versa. The rate at
which the timer reacts to different load steps is set by the chosen time constant (or response rate) per Table 1.
The overload timer can cope with pulsed loads and loads with a complex waveform. Because the rate of
increase and decrease also depends on the load change from the previous load, it also times out faster for
bigger overloads, or allows a smaller overload to run for much longer. The overload timer operates in both
normal CV mode and overload CC mode, or a dynamic mix of both modes.
VO Sample
VIN Sample PIN Compute
P=(VIN x ISW(MID)x(tON/tSW)
VIN
tON tSW
VO
PMEAS(cv)
PLIM(cc)
ILIM x VO
tSMP1
tSMP2
Overload Timer
Integrator
PIN2Overload
Signal To Fault
Mgmt Block
CC/CV Mode
Detect Switch
X2
Block +
-
+
PTRIP2
CS ISW
Sample ISW(MID)
tSMP3
VSENSE 1
3
PPEAK
PTRIP
Time
Overload Trip Point
Example 1: Operation at PRATED continuously; small load
increase after long time ± causes overload timer to trip
Time
Overload Trip Point
Example 2: Operation at low power continuously; step to peak load
causes fastest overload timer ramp-up rate to trip level
PPEAK
PTRIP
Time
Overload Trip Point
Example 3: Operation at low power continuously; repeated short-pulse steps to
peak load ± excessive duty cycle causes eventual overload timer trip
PPEAK
PTRIP
Load Power
Load Power
Load Power
Overload Timer Value
Overload Timer Value
Overload
Timer Value
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Feature Description (continued)
Figure 34. Overload Timer Example Waveforms Under Various Load Scenarios
Figure 35. Overload Timer Block Diagram
SD
GND
VSENSE
CS
HV
VDD
DRV
UCC28630
1
2
3
4
8
6
5
RPROG
40
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Feature Description (continued)
8.3.13 Overload Timer Adjustment (UCC28630 only)
The UCC28630 overload timer trip level and time constant are both selectable from a defined list of
combinations. The user can select the overload timer trip level as a percentage of the rated continuous nominal
power, PNOM (see Figure 41), and the timer response speed. The available choices are detailed in Table 1.
Table 1. Overload Timer Adjustment
RPROG PROGRAMMING RESISTOR (k)
(E96 series values) TIMER CONTINUOUS OPERATION
PTRIP/PNOM (%) TIME CONSTANT AT 200% of PNOM OR IN
CC MODE (ms)
Open, or > 47 160 1000
20.0 160 500
12.7 160 150
9.31 135 1000
7.32 135 500
6.04 135 150
5.11 110 1000
4.42 110 500
3.92 110 150
The desired pull-down resistance on the DRV pin sets the required overload parameters, as shown in Figure 36.
The controller measures the resistance value on the DRV pin at start-up using a low-level test voltage (400 mV
to ensure it is well below the lowest possible power MOSFET gate threshold voltage) and sensing the current
that flows. Thus, based on the resistance RPROG, the required set of timer parameters can be chosen.
Figure 36. Overload Timer Setting Adjustment
(with programming pull-down resistor on DRV pin)
To ensure that the sensed current does not sit close to an interval boundary, the resistor values listed in Table 1
(or the closest value possible) should be used. These recommended resistor values position the test current in
the center of each interval.
41
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8.3.14 CC-Mode IOUT(lim) Adjustment
For the UCC28631, UCC28632, UCC28633 and UCC28634, the pull-down programming resistor on the DRV
pin, as shown in Figure 36, sets the desired CC-Mode limit. The available CC-Mode levels are listed in Table 2,
where the CC limit is given as a percentage of the maximum allowed value from Equation 20.
Table 2. CC-Mode Levels
RPROG (kΩ) CC LIMIT
Open or > 47 100%
20 90%
12.7 80%
9.31 75%
7.32 70%
6.04 65%
5.11 60%
4.43 55%
3.92 50%
8.3.15 Fault Protections
The controller has several built-in fault protections. Most faults are subject to internal persistence filtering to avoid
false-tripping due to noise or spurious glitches from external events. When a fault is detected and persists for the
corresponding filter delay time, the device terminates and disables the PWM drive signal. No PWM activity
occurs if the fault (pin faults for example) is detected at start-up . Table 3 lists all fault sources, persistence
delays and the associated response (latching or auto-restart).
In the case of auto-restart (sometimes called hiccup-mode) faults, the device enters low-power mode for a time
period of tRESET(long) (or tRESET(short) in the case of AC line UV fault and X-capacitor discharge), then discharges
the VDD pin to the VDD(reset) level, followed by a restart attempt. The device continues in a repeating shutdown-
delay-restart loop until the fault is removed. Once the fault clears, the controller restarts automatically, there is no
need to remove and re-apply AC input voltage to the system.
Latching faults do not allow any PWM restart attempts until the AC input voltage is removed. In this case the
controller enters low-power mode. During low-power mode, the device regulates the VDD pin between two levels
VDD(latch_hi) and VDD(latch_lo), as given in Table 6, using the start-up HV current source. This regulation keeps the
controller biased to maintain the latched fault condition as long as AC voltage is present at the input. When the
device loses AC input voltage during latched-fault mode, the controller resets, and restarts when the AC input is
re-applied.
If there is an open-feedback fault due to an open or short on the VSENSE pin or associated external resistor
divider on the aux winding, the output voltage is protected against an over-voltage condition. If the open-
feedback fault occurs before power-up, the fault will be detected by VSENSE pin- fault protection (see next
section 9.3.16), and the controller will not generate any PWM drive signal. This prevents any possible output OV
due to this open-feedback fault condition. If the open-feedback occurs after power-up, when the power stage is
already operating, the open-feedback condition can cause Vout to increase. In this case, the VDD level will also
increase in proportion to Vout (they will track based on the Flyback transformer turns ratio). When the VDD rail
reaches the VDD(ovp) protection threshold, the PWM will be disabled, and the controller will go to fault mode, as
described above. The VDD(ovp) protection is used as an indirect back-up OV protection mechanism for the main
output under running open-feedback fault conditions. The level of output OV depends on the ratio of the normal
VDD regulation level to the VDD(ovp) level. Note that UCC28630/1/2/3 use VDD(ovp) trip level of 17.5 V nominal,
whereas the UCC28634 uses a lower VDD(ovp) of 14.85 V nominal, to ensure a lower/tighter level of output OV
under VSENSE open-feedback conditions. As a result, the user must be careful to choose the number of turns in
the transformer aux winding to ensure that the normal VDD regulation is below the VDD(ovp) protection level, to
avoid false-triggering of the VDD(ovp) protection.
42
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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(1) The filter delay time is either 125 μs or 2 PWM periods, whichever is longer.
(2) The overload timer delay can be programmed as shown in Table 1.
(3) Because these faults are only identified before PWM commences, noise filtering is not required.
Table 3. Fault Sources and Associated Responses
FAULT TYPE TYPICAL CAUSE FILTER
DELAY TIME
RESPONSE
UCC28630 UCC28631,
UCC28632,
UCC28633 UCC28634
VDD OV Excessive transformer leakage; system board
fault 125 μs(1) Latching Auto-restart Auto-restart
VDD UV Insufficient VDD capacitor; system board fault 125 μs(1) Auto-restart Auto-restart Auto-restart
AC brownout AC voltage removal or extended dip 40 ms Auto-restart Auto-restart Auto-restart
OverTemp Internal TJ(max) reached 125 μs(1) Latching Auto-restart Auto-restart
SD pin low External NTC over-temperature event 125 μs(1) Latching Auto-restart Auto-restart
Overload timer Excessive load power for too long Programmable
(2) Auto-restart N/A N/A
Output OV System board fault; system output voltage
back-driven excessively 125 μs(1) Latching Auto-restart Auto-restart
VSENSE pin Short or open detected at start-up No filter (3) Latching Latching Auto-restart
DRV pin Short detected at start-up No filter (3) Latching Latching Auto-restart
CS pin Short or open detected at start-up No filter (3) Latching Latching Auto-restart
Internal fault Internal chip diagnostics fault detected No filter (3) Latching Latching Auto-restart
43
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,
UCC28631
UCC28632
,
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,
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8.3.16 Pin-Fault Detection and Protection
The controller includes protection against most practical pin faults. These faults include open pins, pins shorted
to adjacent pins, pins shorted to GND and pins shorted to VDD. The device performs pin fault checking at start-
up, before the PWM is enabled. Table 4 summarizes the response to pin faults. Most faults cause either a
latched shut-down, or failure to start-up. For UCC28634, all pin-faults are non-latching.
A short-circuit from the HV pin (pin 8) to the VDD pin (pin 6) is unlikely to occur, because pin 7 is not included in
the package. The HV pin and tracking requires additional PCB spacing in any event to meet creepage
requirements. However, if such a fault does occur, the device continues to charge the VDD capacitor through the
HV pin external series resistor, and the power supply starts up and appears to operate normally. But because the
HV and VDD pins are shorted, the internal HV current source cannot switch-out the external HV resistor, so it
always dissipates power. This condition results in a large increase in no-load standby power. A 200-kΩexternal
HV resistor, dissipates 66 mW at 115 VAC, and 265 mW at 230 VAC. At load levels where the X-capacitor
discharge function is operational, the short to VDD appears to be an AC-disconnect event, and causes the
device to cycle on and off.
Table 4. Pin Faults and Associated Responses
PINS OPEN ADJACENT SHORT GND SHORT VDD SHORT
NAME NO.
VSENSE 1 Latched fault Latched fault Latched fault No start-up
SD 2 Normal operation Latched fault Latched fault Latched fault
CS 3 Latched fault Latched fault Latched fault No start-up
GND 4 Device fails, power supply
damaged Latched fault N/A No start-up
DRV 5 Hiccup fault No start-up Latched fault No start-up
VDD 6 No start-up No start-up No start-up N/A
no pin 7 N/A N/A N/A N/A
HV 8 No start-up N/A No start-up Fault not detected/Hiccup
fault
+
+
Over
Temperature
4V5
210 mA
2.0 V
SD
GND
VSENSE
CS
HV
VDD
DRV
UCC28630
1
2
3
4
8
6
5
RADJ
to
NTC
R1 at 25°C
R2 at TTRIP
44
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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8.3.17 Over-Temperature Protection
The controller has built-in thermal protection. If the controller junction enters an over-temperature condition, the
controller shuts down. The fault response (latching or auto recovery) depends on the device variant, per Table 3.
There is 10°C hysteresis in the over-temperature trip point, the controller only restarts if the junction temperature
has dropped by at least 10°C below the trip level.
8.3.18 External Fault Input
An external fault input signal may be applied to the controller SD (shutdown) pin. This signal forces the controller
into fault mode. To trigger the fault, the voltage on this pin should be pulled below the fault trip threshold. A
typical application is shown in Figure 37, where this pin is used to shut down the controller in the event of an
over-temperature event as detected by a NTC (negative temperature coefficient) thermistor. The device pulls up
the SD pin internally using a current source. As temperature rises, the external NTC resistance decreases,
reducing the voltage on the pin. When the pin voltage drops to the fault trip threshold, the controller enters fault
mode. The fault response (latching or recovery) depends on the device variant, per Table 3.
Figure 37. Fault Interface to SD Pin
The required trip resistance can be calculated from the internal trip voltage and pull-up current source. Nominally,
this is 9.5 kΩ. Choose the NTC should so that it can achieve this value of resistance at the desired hot-spot trip
temperature. If the NTC resistance is too low at the required trip temperature, connect a standard chip resistor in
series to bring the total resistance up to 9.5 kΩ.
The device internally filters the SD pin with persistence delay as listed in Table 3. An external filter capacitor is
not normally necessary. However, if an application uses an external filter capacitor, the value should be limited to
1 nF maximum. A larger value may impact the useful life of the controller.
VOUT
LED
+
+
TL103W
2.5 V
SD
GND
VSENSE
CS
HV
VDD
DRV
UCC28630 1
2
3
4
8
6
5
Wake-up
signal +
+
2.2 V to
RPULLUP
45
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,
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UCC28632
,
UCC28633
,
UCC28634
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8.3.19 External SD Pin Wake Input (except UCC28633)
During low-power modes (when fSW < fSMP(max)), the device disables the internal pull-up on the SD pin. This
action allows the pin voltage to fall to GND, and the SD pin then functions as a transient wake-up input. In this
case, if the pin rises above the wake threshold while the device is in low-power sleep mode, the device wakes
and starts PWM pulses immediately. This feature is useful for applications that require a faster response to load
transients from zero or near-zero load, where a wake-up signal can be appropriately coupled to the SD pin from
the secondary side.
Figure 38 describes a typical secondary-side wake circuit and coupling of the wake signal to the controller on the
primary side. This circuit uses a TL103W component which is an integrated reference plus two op-amps in a
convenient SOIC-8 package. Both op-amps are connected to the same internal 2.5-V TL431 type reference, with
a 3-resistor divider chain allowing each op-amp to monitor a different level. The upper op-amp output is low as
long as the device is regulating the output voltage normally. If a sufficiently large load transient occurs while the
primary-side controller is in sleep mode, the output voltage drops below a transient wake level. The upper op-
amp output goes high, driving current through the low-cost wake signal opto-coupler. On the primary side, the
wake opto-coupler pulls up the SD pin above the wake threshold and forces PWM switching as a reaction to the
load transient.
The lower op-amp section monitors the output voltage and its output goes low only when the output voltage is
above a minimum enable threshold for the secondary-side wake-up monitor. This action is necessary so that
under certain conditions, such as a start-up sequence or short-circuit condition (when the output voltage is
already below the transient wake level) that the secondary-side circuit does not continually drive the wake opto-
coupler, which could activate an SD pin fault during pin-fault checking at start-up.
Figure 38. Typical Secondary-Side Voltage Monitor and Wake-Up Circuit for Interfacing to the SD Pin
SD
GND
VSENSE
CS
HV
VDD
DRV
UCC28633
1
2
3
4
8
6
5
EMC
Filter
to
VAC
VOUT
UCC24650
5 1
2
VDD
GND
WAKE
46
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,
UCC28631
UCC28632
,
UCC28633
,
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8.3.20 External Wake Input at VSENSE Pin (UCC28633 Only)
The UCC28633 device variant supports fast PSR transient response via the VSENSE pin. When the loop
demand drives the modulator frequency below approximately fSMP(max), the controller enters a low-power sleep
mode for a portion of the switching cycle. The sleep interval varies, depending on the switching frequency
commanded. The sleep interval is longer for lower switching frequency, and longest at fSW(min). For conventional
PSR controllers, if a load transient occurs during this sleep interval, the controller will not react until the next
timed wake-up, during which the output voltage can drop significantly, depending on the size of the load step and
the amount of output capacitance.
The UCC28633 can respond to fast transient wake signal coupled to the VSENSE pin. If the wake signal
exceeds an internal pin threshold VSENSE(wake) while the controller is in sleep mode, the sleep interval is
terminated and PWM activity commences within a typical delay time of tWAKE. This dramatically improves the
response to heavy load transients from zero load, or very light load. If the switching frequency is above fSMP(max),
the controller never enters sleep mode, so wake response on the VSENSE pin never enabled. The
commencement of any sleep interval in the controller is delayed until the resonant ringing on the VENSE pin has
decreased below the VSENSE(wake) threshold for at least 2 µs. Once the ringing has decreased, the wake response
is enabled, and the sleep interval commences.
Figure 39. UCC24650 Secondary-Side Voltage Monitor and Wake-Up Circuit
SD
GND
VSENSE
CS
HV
VDD
DRV
UCC28633
1
2
3
4
8
6
5
EMC
Filter
to
VAC
VOUT
UCC24650
Q1
R1 R2
5 1
2
VDD
GND
WAKE
47
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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The wake signal at the VSENSE pin can be generated using a secondary side low power voltage monitor such
as UCC24650, as shown in Figure 39. Further details can be found in the datasheet for UCC24650. This
secondary-side monitor uses the switching activity on the secondary winding to trigger refresh of an internal
sample-and-hold circuit to measure and record the system output voltage at the VDD pin. Thereafter, if the actual
output voltage, sensed at the VDD pin, drops by ΔWAKE% (see UCC24650 detailed datasheet specifications) of
the previously sampled value, the WAKE pin is internally pulled low through a current-limited open-drain switch.
As shown in Figure 39, the main output rectifier diode is positioned at the return side of the secondary winding,
so that the GND-referenced UCC24650 WAKE function can be deployed. In effect, the WAKE pin shorts out the
rectifier diode for a short interval (see UCC24650 detailed datasheet specifications), to draw some current from
the output capacitor through the transformer secondary winding. This sets up a low-level pulse of current that
then rings resonantly in the power circuit magnetizing inductance and parasitic capacitance. The ringing causes
a similar ringing voltage waveform on all transformer windings, including the bias/sense winding, which interfaces
to the VSENSE pin. If the initial pulse of current drawn by the secondary WAKE pin is sufficient, then the ringing
voltage at the VSENSE pin is large enough to exceed the VSENSE(wake) threshold.
The UCC24650 datasheet Application Information section includes details of how to estimate the amplitude of
the wake-pulse ringing at the WAKE pin. In some cases, especially at higher rated output power, the transformer
magnetizing inductance is lower, while the total switch node capacitance tends to be higher. This reduces the
transformer impedance, and can also result in reduced wake pulse amplitude. In these cases, the UCC24650
WAKE pin output can be augmented with an external PNP circuit Q1, R1 and R2, as shown in Figure 40. In this
case, when the WAKE pin pulls low, Q1 turns on, and draws more current through the secondary winding. A
current limiting resistor R1 is recommended in series with either collector or emitter. Effectively R1 swamps the
UCC24650 internal WAKE pin resistance, RWAKE. A pull-up resistor R2 from base to emitter is also required, to
ensure that the WAKE pin is adequately pulled up/down during normal switching activity to properly trigger the
internal sample and hold on the VDD pin. The external PNP device Q1 must have at least the same voltage
rating as the main rectifier diode.
Figure 40. Augmented UCC24650 Secondary-Side Voltage Monitor and Wake-Up Circuit
0%
P0 12.5%
P1 30%
P2 45%
P3 70%
P4 100%
P5
0.2
30
60
150
0
170
400
640
800
Frequency
(kHz) VCS(pk)
(mV)
Control Loop
Demand Level
0.025%
PNOM
3.5%
PNOM
20%
PNOM
40%
PNOM
100%
PNOM
>=200%
PNOM
Approximate
Power Level
120
48
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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8.3.21 Mode Control and Switching Frequency Modulation
The flyback controller supports applications that require a wide range of operating power levels. This range can
include effectively zero output power in standby conditions, up to a maximum rated continuous power, and then
beyond this, to a mode of peak operating power for a limited time. The modulator operates in multiple modes to
support these power requirements in an efficient way. In some regions, the modulator operates in AM mode at
fixed frequency, where the device adjusts the amplitude of the peak current to regulate the output. In other
regions, the modulator operates in FM mode at fixed peak current, where the device adjusts the switching
frequency to regulate the output. By adjusting only peak current or frequency, (depending on operating region)
the control loop smoothly regulates the power flow of the power stage. The shape of the modulator gain curve
helps counteract the increasing power stage gain as load is decreased.
In the high-power region of the modulator, the device adjusts both peak current and frequency together, to allow
higher power delivery with a modest increase in peak current. In this high-power region, the power stage typically
transitions into continuous-conduction mode (CCM), particularly at low line. The combination of up to
frequency increase and 1.25× peak current increase in CCM allows up to peak power delivery capability for a
given transformer size. Figure 41 provides details regarding the modulator peak current (in mV at the CS pin)
and switching frequency variation vs power demand level. The frequency adjusts from a minimum of 200 Hz up
to a maximum of 120 kHz. The peak-current sense voltage at the CS pin varies from 172 mV to 800 mV. Table 5
summarizes the modulator breakpoints and corresponding percentage power levels.
Figure 41. Modulator Modes and Frequency Variations with Power Level
49
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
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For no load and very light loads (P0to P1region) the modulator operates in a pulse frequency modulation (PFM)
mode. In PFM mode, the device maintains a constant peak current in the transformer magnetizing inductance, so
that the energy transferred in each switching cycle is fixed. The magnetic sensing, fixed-point sampling scheme
requires that the device always imposes a minimum peak current. This minimum peak-current demand naturally
results in a minimum transformer magnetizing volt-second product that the device maintains across the input line
voltage range. Ensuring a minimum on-time magnetizing volt-seconds also ensures a balancing volt-second
flyback interval, during which the device guarantees the availability of the output voltage sample. Magnetic
Sensing: Power Stage Design Constraints outlines the transformer design constraints necessary to comply with
the minimum on-time and minimum required volt-seconds.
In the P0to P1region, the energy transfer per switching cycle is maximized, which in turn minimizes the switching
frequency and associated switching and drive losses, to improve efficiency. However, due to concerns about
audible noise in this region, the peak current VCS(min) in this region is limited to 22% of the peak VCS(max) at the
maximum demand level. This peak-current derating maintains the transformer peak flux density to 22% of the
peak, to minimize transformer-induced audible noise. Assuming a maximum peak flux density of typically 300 mT
at highest peak current, this derating sets the peak flux level at approximately 65 mT in the light-load region.
Empirically, this flux level greatly reduces magnetic audible noise for a variety of power levels and transformer
designs. In this region, the use of sleep modes (where most of the device internal blocks are powered down in
between switching cycles) minimizes the controller power consumption. Minimizing controller power consumption
helps reduce total standby power consumption, and also greatly eases the bias design constraints.
For higher loads above P1(P1to P2region), the device fixes the modulator frequency at a low value above the
audible range, while the peak switch current ramps up from the minimum level, to deliver the increased output
power. Maintaining a fixed low-switching frequency while ramping peak current, minimizes switching losses to
provide good light-load efficiency.
For higher loads above P2(P2to P3region), the device maintains a constant peak-switch current, while the
modulator frequency ramps to its nominal operating value. The normal heavy load (between 40% and 100% of
rated) operating power range lies between P3and P4. In this region the device maintains a constant switching
frequency at the nominal value fSW(nom), and the peak switch current ramps to achieve increased output power.
Fixed-frequency operation at nominal operating power results in consistent EMI and transient load step
performance.
Table 5. Frequency and Peak-Current Modulator Operating Ranges and Breakpoints
MODULATOR
BREAKPOINT DEMAND LEVEL
(%) APPROXIMATE
POWER
LEVEL % of
PNOM
VCS PEAK FREQUENCY fSW
(mV) (kHz)
PO0 0 0.025 172 VCS(min) 0.200 fSW(min)
PO1 12.5 3.5 172 VCS(min) 30 fSW(LL)
PO2 30 20 400 VCS(nom) 30 fSW(LL)
PO3 45 40 400 VCS(nom) 60 fSW(nom)
PO4 70 100 640 VCS(bcm) 60 fSW(nom)
PO5 100 > 200 800 VCS(max) 120 fSW(max)
0% 25% 50% 70% 100%
100%
PNOM
>=200%
PNOM
Power Level
Peak Power Region
± DCM/CCM
Operation (Line
dependent)
380 V 75 V
100 V
Linear Gain
0.025%
PNOM
14%
PNOM
47%
PNOM
100%
PNOM
>=200%
PNOM
Approximate
Power Level
Control Loop
Demand Level
DCM
Operation Up
to Prated
50
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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The peak-power range lies between P4and P5. In this region the transformer can operate in CCM depending on
loading and line voltage. By increasing the frequency appropriately, higher average input current can be
processed for the same peak current, so the transformer size does not need to increase substantially for a high-
rated transient peak power. The modulator does, however, also increase the peak current in this region of
operation, requiring a modest increase in transformer size, but this allows a larger transient peak power to be
delivered. The modulator control loop adjusts both the frequency and peak current according to the power
demand so that the increased frequency and peak current meets the load demand.
Figure 42 shows the modulator gain curve, specifically the non-linear modulator gain vs load. At very light loads,
the modulator gain remains low, to help counteract the effect of the higher power stage gain as the load
resistance increases. This low gain helps stabilize the magnetic regulation loop in the light load territory, where
the output voltage sample rate drops with decreasing switching frequency. At heavier loads, the modulator gain
progressively and smoothly increases to help improve transient response. When the switching frequency
increases above the maximum magnetic sense sample rate (fSMP(max)), the magnetic sense voltage control
sample rate is clamped.
Figure 42. Modulator Gain Curves vs Bulk Capacitor Voltage
(fNOM - 6.7%)
(fNOM + 6.7%)
fNOM
6 ms
51
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,
UCC28631
UCC28632
,
UCC28633
,
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8.3.22 Frequency Dither For EMI (except UCC28632)
To help ease EMI compliance of the system, the device dithers the switching frequency over time. This dithering
of frequency is active only above the light-load region threshold (PLL(%)) point on the modulator curve. In the light
load regions, frequency dither is disabled. The frequency dither follows a repeating pattern, in the sequence:
{(fNOM), (fNOM + 6.7%), (fNOM + 6.7%), fNOM), (fNOM 6.7%), (fNOM 6.7%), (fNOM),....}
The controller dwells at each frequency for 1 ms. The pattern repeats every 6 ms, as shown graphically in
Figure 43.
NOTE
The device always dithers frequency between 6.7% and –6.7% at every operating point in
the modulator. The dither frequency delta is not an absolute delta, it scales with actual
operating frequency, depending on the exact operating point value.
Figure 43. Frequency Dither Pattern Details
In order to balance the power flow and reduce and output ripple as a consequence of frequency dithering, the
device automatically adjusts peak-current demand in inverse-proportion to the square-root of the frequency dither
deviation. Thus, since the power flow (in DCM) is given by × L × I2× fSW), this balances the power flow, and
cancels the output ripple as a consequence of frequency dithering.
52
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
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8.4 Device Functional Modes
8.4.1 Device Internal Key Parameters
The application designer requires some key device internal parameters in order to calculate the required power
stage components and values for a given design specification . Table 6 summarizes the key parameters.
Table 6. Key Internal Device Parameters
PARAMETER DESCRIPTION VALUE UNIT
ACON
Minimum AC mains input RMS voltage to allow initial start-up, or restart, UCC28630,
UCC28631, UCC28632, UCC28633 80 VAC
Minimum AC mains input RMS voltage to allow initial start-up, or restart, UCC28634 68 VAC
ACOFF
Minimum AC mains input RMS voltage below which PWM stops, UCC28630,
UCC28631, UCC28632, UCC28633 65 VAC
Minimum AC mains input RMS voltage below which PWM stops, UCC28634 58 VAC
tUV(delay) Delay time for which AC mains must remain below ACOFF level to disable PWM, i.e.
brownout delay time 40 ms
tRESET(short) Delay time in sleep mode before restart is initiated applies to ACUV, X-capacitor
discharge responses 500 ms
tRESET(long) Delay time in sleep mode before restart is initiated applies to all other auto-restart
faults 1,000 ms
fSW(uv) Switching frequency used during initial 3-cycle exploratory pulses for ACON detection
at start-up 15 kHz
tON(max_uv) Maximum on-time used during initial 3-cycle exploratory pulses for ACON detection at
start-up 2.3 µs
KLINE Device internal line sense gain factor 49.25
KCC1 Device internal CC mode gain factor 44.5
KCC2 Device internal CC mode offset factor 69.5
fSMP(max) Maximum magnetic sense sample rate; in effect when fSW > fSMP(max) 16 kHz
VDD(latch_hi) Upper VDD regulation level during latched fault mode 10 V
VDD(latch_lo) Lower VDD regulation level during latched fault mode 8 V
tON(hv) HV current source on-time during X-capacitor sampling 20 µs
tSMP(hv) HV current source sample repetition rate during X-capacitor sample burst 1 ms
tWAIT(hv) HV current source wait-time between X-capacitor sampling bursts 200 ms
PLL(%) Light-load region threshold as % of PNOM 12.5%
VDD(sc) VDD short-circuit threshold below which charging current is limited 1.0 V
tPROP(gate) Internal PWM comparator + latch + gate driver aggregate delay 100 ns
tSTART(del) Internal start-up initialization delay 3 ms
VSENSE(wake) VSENSE pin wake threshold for fast transient response (UCC28633 only) 0.8 V
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9 Applications and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The UCC2863x device is a highly integrated primary-side-regulated (PSR) flyback controller, supporting
magnetically-sensed output voltage regulation via the transformer bias winding. This sensing eliminates the need
for a secondary-side reference, error amplifier and opto-isolator for output voltage regulation. The device delivers
accurate output voltage static load and line regulation, and accurate control of the output constant-current limit.
The fixed-point magnetic sampling scheme allows operation in both continuous conduction mode (CCM) and
discontinuous conduction mode (DCM). The combination of the sampling scheme and high current gate driver
source and sink capability, makes this device ideal for high power flyback converters up to 100 W and beyond.
The modulator adjusts both frequency and peak current in different load regions to maximize efficiency
throughout the operating range. The control approach improves performance (efficiency, size and cost) and can
reduce transformer size and cost by allowing operation in CCM with FM during peak overload conditions. The
modulator supports peak-to-average transient overload power up to 200% of the nominal average rating.
9.2 Typical Application
9.2.1 Notebook Adapter, 19.5 V, 65 W
This design example describes the PWR572 EVM design and outlines the design steps required to design a
constant-voltage, constant-current flyback converter for a 19.5-V/65-W notebook adapter. For all equations and
design steps, refer to Table 6 for definitions and values of key internal device parameters that are relevant for
calculations of external component values.
Minimize copper area
also High voltage Net
of VSW net
Minimize copper area
of net
Connect 2 pins
of bobbin to
Vsec and Ret nets
47.0
R11
0.2
R16
0.1µF
C4
TP9
TP6
TP7
2200pF
C9
TP8
TP10
1µF
C3
4.7
R13
100V
D5
0603
C10
1206
R17
39k
R8
100k
R15
100
R4
TP3
TP5
4.70
R1
120pF
C6
3.90k
R10
TP2
1.00k
R5
BAV70-V
D4
0
R6
-VPRI
VDD
+VOUT
VDC
ACA
ACB
VSEC
+VSW
-VPRI
-VPRI
STARPT
DRV
CS
-VPRI
MAG
MAG
DRV
RET
STARPT -VPRI
TP1
TP4
F1
39213150000
V1 0.33µF
C1
1000V
D3
1N4007
1000V
D2
1N4007
100k
R3
MURS160-13-F
D6
1
3 2
600V
Q1
STF13NM60ND
180k
R9
22.6k
R7
470k
RT1
NT1
Net-Tie
22µF
C2
ES1D-13-F
200V
D1
100V
D7
NTST30100CTG
VSENSE 1
SD 2
CS 3
GND 4
DRV
5
VDD
6
HV
8
U1
UCC28630D
MAG
-VPRI
21
J1
~
3
+1
~2
-
4
800V
BR1
47.7µH
13
L2
RLTI-1098
LINE
NEUTRAL GND
HV
GND
MAG
GND
+VOUT
0
R20
27µF
C7
1000pF
C14
D10
100k
R2
10pF
C15
8.20k
R18 OUTPUT R/A
SOCKET
1 2
34
4.5mH
L1
RLTI-1099
STARPT
1206
R12
0805
C8
82V
D8
1SMB5947BT3G
100V
D9
1SMB5949BT3G
10pF
C16
1
2
3
4
5
J4 +VOUT
RET
TP11
VDD
100µF
C5
1
2
J2
Green
LED1
88VAC - 230VAC
0.5A - 1.5A
18.5V - 20.5V
0A - 7A
DANGER HIGH VOLTAGE
680µF
C12
1µF
C13
680µF
C11
1
2
11
8
5
4
6
9
10
T1
RLTI-1100
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Typical Application (continued)
9.2.2 UCC28630 Application Schematic
Figure 44. Typical Application Circuit for 19.5-V / 65-W Adapter
CBULK=
P
OUT
D × L0.5+ 1
N × sin-1 FV
BULK:min ;
¾2 × V
AC:min ;GM
k2 × V
AC:min ;
2FV
BULK:min ;
2o × fLINE:min ;
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Typical Application (continued)
9.2.3 Design Requirements
Table 7. Design Requirements
DESIGN PARAMETER TARGET VALUE
Output voltage 19.5 V
Rated (continuous) output power 65 W
Peak (transient) output power 130 W
Peak (transient) output power duration 2 ms
Input AC voltage range 88 VRMS to 264 VRMS
Typical efficiency 88%
Minimum bulk voltage at 88 VAC/47 Hz and rated (continuous) output power 82 V
9.2.4 Detailed Design Procedure
9.2.4.1 Custom Design With WEBENCH® Tools
Click here to create a custom design using the UCC2863x device with the WEBENCH® Power Designer.
1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements.
2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.
3. Compare the generated design with other possible solutions from Texas Instruments.
The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time
pricing and component availability.
In most cases, these actions are available:
Run electrical simulations to see important waveforms and circuit performance
Run thermal simulations to understand board thermal performance
Export customized schematic and layout into popular CAD formats
Print PDF reports for the design, and share the design with colleagues
Get more information about WEBENCH tools at www.ti.com/WEBENCH.
9.2.4.2 Input Bulk Capacitance and Minimum Bulk Voltage
The required bulk capacitance value depends on the target minimum bulk capacitor ripple voltage at minimum
AC input line, minimum line frequency and on the power level of interest. As a way of estimating, use 1.5-μF to
2-μF per Watt of rated, continuous power to achieve approximately 70 V to 80 V minimum at 88 VRMS input. This
case indicates a required bulk capacitance of between approximately 100 μF and 130 μF. Alternatively, the
required capacitance may be explicitly calculated for a specific set of requirements using Equation 21.
(21)
Using the parameters in Table 7, this calculates a required CBULK of 130 μF.
To help reduce differential mode (DM) emissions for conducted EMC compliance, the bulk capacitance has been
split into two separate capacitors C5 and C7 in Figure 44, with a small DM choke L2 inserted between the
capacitors. The total resulting capacitance of 127 μF is close to the required minimum requirement per
Equation 21, and the design results in a small decrease in the actual bulk capacitor minimum ripple voltage.
Next, verify that the choice of bulk capacitance satisfies the X-capacitor discharge constraints for rate of
discharge by the load when X-capacitor sampling is inactive, per Equation 5. The bulk capacitance should be
less than the value calculated by Equation 22.
CBULK Q
2@P
NOM
DA× P
LL(%) × tDIS
kVAC:pk ;2 F VSELV2o=2:65 × 0.125; × 1
:3732 F 602;LsuxJF
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(22)
LPRI=
1
2 × @P
RATED
DA × L1
V
BULK:min ;+1
NP
NS
× :V
OUT+V
RECT;M2
× fSW:nom ;
NB
NS
=V
BIAS:target ; + V
F
:V
OUT + V
RECT;
NP
NS
=VAC:pk _max ;
kVREV:rated ; × %Deratingo F :VOUT + VRECT;
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9.2.4.3 Transformer Turn Ratio
Choose the transformer primary-to-secondary-side turns ratio based on the allowed voltage stress for the output
rectifier, or the primary MOSFET. For 19.5-V charger designs, it is valid to choose a turns ratio that allows the
use of a more efficient 100-V Schottky rectifier.
(23)
For a good Schottky diode with 100-V reverse rating, VREV(rated), the rectifier forward voltage drop, VRECT, can be
expected to be in the range of 0.4 V to 0.5 V at 3 A to 5 A, at practical operating temperatures in the region of
100°C. Allowing an 85% derating on the rectifier reverse voltage stress, Equation 23 indicates a required turns
ratio of 5.734 for a maximum AC peak voltage of 373 V (264 VRMS).
Choose the bias winding turns ratio to set the nominal bias voltage for the device VDD pin. Use an initial
VBIAS(target) of 12 V.
where
VFis the forward voltage drop of the rectifier on the bias winding. (24)
For a typical 0.7-V bias-diode drop, this equation calculates to 0.6366.
When the transformer size and type are chosen, the actual turns values can be calculated. Because the turns
need to be rounded to integer values, the actual turns ratios achieved deviates from these targets. Check the
final ratios to ensure that the secondary-side Schottky rectifier stress and the bias winding nominal level are
acceptable. Adjust the specific turns counts to meet the target ratios.
9.2.4.4 Transformer Magnetizing Inductance
Match the power stage design to the modulator curves by ensuring that the boundary conduction mode (BCM
boundary of operation between DCM and CCM) point coincides with the minimum bulk-capacitor voltage at
minimum line, at rated output power. This choice results in DCM operation at all line voltages for all loads up to
continuous rated load, and minimizes power loss and EMC impacts due to output rectifier reverse recovery
during CCM operation. This design choice allows operation to extend into the CCM region of operation as
required to deliver the transient peak load.
To achieve this design target, the required primary magnetizing inductance, LPRI is calculated from Equation 25.
In this equation, the value of FSW(nom) is 60 kHz, taken from the modulator curve region P3to P4,inTable 5. The
value of VBULK(min) is the value that occurs with the actual used bulk capacitance of 127 μF.
(25)
This calculates a value of 257 μH. Round the value to 260 μH.
RCS
LPRI
Q1
VIN:pk _max ;
× VCS:min ;
tON:min ;
=172 mV
373 V × 0.6 Js yyr
RCS
LPRI
QV
CS:min ;
tOUT:smp ;
× NS
NP
× 1
:VOUT + VRECT;=172 mV
säyJs × 6
34 × 1
:19.5 V + 0.4 V; {rr
RCS =
V
CS:bcm ;
2 × @P
RATED
DA × L1
V
BULK:min ;+1
NP
NS
× :V
OUT + V
RECT;M
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9.2.4.5 Current Sense Resistor RCS
In addition to choosing LPRI value to map the rated power to the target BCM point at minimum bulk voltage,
choose the RCS value according to Equation 26. This calculation ensures that the resulting peak current, in
conjunction with the chosen value of magnetizing inductance, and the 60-kHz modulator frequency, delivers the
required input power to meet the rated output load power, at minimum bulk voltage ripple.
where
VCS(bcm) is the modulator peak-current sense level at point P4(640 mV) (26)
This equation calculates a value of 207 mΩ. Use the nearest standard E24 value of 200 mΩ.
9.2.4.6 Transformer Constraint Verification
As outlined in Magnetic Sensing: Power Stage Design Constraints, there are constraints on the ratio of RCS/LPRI
to ensure the design is consistent with the required volt-seconds for output sampling at minimum load, and with
the controller tON(min) at high line. Per Equation 15 and Equation 16, limit the ratio of RCS/LPRI.
(27)
and,
(28)
In this case, the ratio equates to 769, so both constraints are met.
dSEC = 1 Fd
d =
NP
NS
× :V
OUT + V
RECT;
FV
BULK:min ;+NP
NS
× :V
OUT + V
RECT;G
ITOT = IPK × §d
3
W + IPK × §dSEC
3
W
KG:des ;=
LPRI
2 × IPK:sat ;
2 × ITOT
2 × OCU
Bmax
2 × KU × P
CU
KG =
Ae
2 × AW
MLT
IPK:max ; =
V
CS:max ;
RCS
IPK:sat ;=
V
CS:max ; × ¾106.7%
RCS
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9.2.4.7 Transformer Selection and Design
After determining the value of current sense resistor RCS, determine the maximum peak current at maximum
demand point on the modulator. Accommodate for the IPEAK adjustment for frequency dithering. Use this value
when calculating the margin for core saturation. In this case, IPK(sat) calculates to 4.13 A.
(29)
In subsequent calculations of required primary turns etc, the average maximum peak current, IPK(max) , during the
frequency dither period should be used, which calculates to 4.0 A.
(30)
Knowing IPK(max), LPRI and the turns ratio, the choice of transformer size and core shape and type dictates the
required number of primary, secondary and bias turns, and the size of the air-gap. Various trade-offs, design
preferences, and transformer design targets (size, cost, target losses, etc.) influence the specific choice of
transformer core in any given design.
In the case of the UCC28630EVM-572 (PWR572 EVM), core area-product geometry was used to choose the
minimum core size available to meet the power level. The core geometry factor Kgis a figure-of-merit that
reflects the core power capability, in terms of its physical size, shape and design. It combines the core effective
cross-sectional area, Ae, winding window area, Aw, and the mean length per turn (MLT) of wire around the core.
(31)
Estimate the required design core geometry, KG(des), using the required transformer inductance LPRI, maximum
peak current IPK(max), allowed maximum core flux density Bmax and a target copper loss budget, PCU.
where
ρcu is the resistivity of Copper (approximately 1.7 × 10-8 Ωm at room temperature, 2.2 × 10-8 Ωm at 100°C),
Kuis a winding window utilization factor that accounts for the percentage of the window that is occupied by
Copper (32)
Kucan often be as low as 25%, due to the fill factor (gaps between wires), wire insulation (especially for triple-
insulated wire), and the need for insulating tapes and EMC shielding layers. The estimate of the required core
geometry needs an estimate of the aggregate total winding current ITOT. The analysis models the flyback
transformer primary and secondary windings as a single lumped non-isolated inductor (such as a single winding
buck inductor), only for the purpose of sizing the required core winding window to achieve the target copper loss.
In this case, the secondary-side current amplitude reflects to the primary side so that aggregate total primary
current. ITOT can be estimated in Equation 33.
where
d is the primary on-time duty cycle
dSEC is the secondary-side flyback period duty cycle (33)
At rated power and minimum bulk capacitor voltage, the inductance LPRI has been chosen to achieve boundary-
mode conduction, therefore the duty cycle is given in Equation 34.
(34)
and (35)
AL =
LPRI
NP
2 =
txrJ
342= 225 nH
V
BIAS = :V
OUT + V
RECT; ×
NB
NS
F V
F=:19.5 + 0.45; ×
4
6 F 0.7 = 12.6 V
NB = VBIAS:target ; + VF
:VOUT + VRECT; × NS = 12 + 0.7
19.5 + 0.45 × 6 = 3.82
NP
NS
5.734 = 98.8%
NS =
NP
5.734 = 5.93
NP =
LPRI × IPK:max ;
Bmax × Ae
=
txrJ× 4.0
0.315 × 96.6 J = 34.18
KG:RM10 ; = (96.6 × 10-6)2 × (44.2 × 10-6)
(52 × 10-3) = 7.932 × 10-12
KG:des ;=
txrJH2 × 4.132 × 2.62 × 2.2 × 10-8
0.3152 × 0.25 × 1.0
ITOT =
V
CS:bcm ;
¾3RCS
×
Ï
Î
Î
Î
ͪNP
NS
× :V
OUT+V
RECT;
FV
BULK:min ;+NP
NS
× :V
OUT+V
RECT;G+©V
BULK:min ;
FV
BULK:min ;+NP
NS
× :V
OUT+V
RECT;G
Ò
Ñ
Ñ
Ñ
Ð
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At the boundary conduction point, the primary peak current IPK is at the level set by the modulator, VCS(bcm). So
from Equation 33, ITOT becomes Equation 36.
(36)
Equation 36 calculates ITOT as 2.6 A. Thus the required design KG(des), assuming KUof 25%, Bmax of 315 mT and
a target of 1-W copper loss, is shown in Equation 37.
(37)
Equation 37 indicates that this design requires a core size and shape with a KGof more than 6.9 × 10-12. A
review of commonly used cores indicated that the RM10/I core set meets this requirement. With Aeof 96.6 mm2,
Awof 44.2 mm2and mean length per turn (MLT) of 52 mm, KG(RM10) is 7.9 × 10–12, giving some margin over the
design target.
(38)
With the chosen core, the actual primary, secondary-side and bias turns can be calculated. The required primary
turns depend on the allowed Bmax. For most power ferrites, a value in the region of 315 mT is commonly used.
(39)
Round NPto 34. Now the required secondary-side turns can be calculated, using the previously calculated turns
ratio per Equation 23.
(40)
Again, NSis rounded to 6. Due to the integer rounding of the turns count, ensure that the actual turns ratio is
within 5% of original target (if outside this range, secondary-side rectifier or primary MOSFET stress may be too
high).
(41)
From Equation 24, the required bias turns can be calculated using Equation 42.
(42)
Again, NBis rounded to 4. The effect of integer scaling in the turns is verified by calculating the expected bias
voltage versus target.
(43)
The VBIAS target was 12 V, so this is acceptable.
The required core inductance factor, AL, to achieve the target inductance can be calculated as in Equation 44.
The transformer manufacturer uses this factor to gap the core center leg.
(44)
lg = F342 × vN × 10F7 × 102.31 J
260 JG F l44.6 m
5500 ×102.31 J
96.6 Jp LwxuärJm
lg =F NP2 × J0 × Ag
LPRI G F llm
Jr
× Ag
Aep
Ag = ACENTRE × F1+ lg
DCENTREG2
L{uäuJ × l1+ 0.514
10.9 p2
= 102.31 mm2
lg = 342 × vN× 10-7 × 93.3 J
txrJF44.6 m
5500 LwsvJm
lg = NP2 × J0 × ACENTRE
LPRI
Flm
Jr
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Finally, calculate the required air-gap length lg, based on the required inductance and the core geometry.
where
μ0is the permittivity of free-air
μris the relative permeability of the chosen core ferrite material
ACENTRE is the cross-sectional area of the core center leg
lmis the core average magnetic path length (45)
For the RM10/I core in 3C95 material (chosen for low core loss over a wide temperature range), the required air-
gap length is calaulated using Equation 46.
(46)
Typically, the air-gap calculation in Equation 45 underestimates lg, due to flux fringing in the air-gap. The fringing
causes the affective area of the air-gap Agto be somewhat larger than the ferrite core center leg ACENTRE,
depending on the gap length. This difference requires an increase in the required air-gap length to get the
required inductance, which results in a further increase in fringing. However use Equation 45 to determine an
initial value for lg, which can then be used to estimate Ag. For round centre legs, the increase in effective area
within the gap can be estimated empirically from Equation 47
where
DCENTRE is the center leg diameter (47)
(For more information about this subject, download the paper Inductor and Flyback Transformer Design, Lloyd
Dixon, TI Power Supply Design Seminar SLUP127).
Because Equation 45 assumes that Agequals ACENTRE, it must be modified using Equation 48.
(48)
Re-iterating the air-gap calculation in Equation 49 .
(49)
Typically, after the second iteration above in Equation 48, the estimated air-gap is very close to the required
value. Further iterations can be made, but should not be necessary.
IPRI:rms ; =
V
CS:bcm ;
¾3RCS
× ªNP
NS
× :V
OUT + V
RECT;
FV
BULK:min ; + NP
NS
× :V
OUT + V
RECT;G =
0.64
¾3®0.2
× ¾0.58 = 1.41 A
VDS:max ; = VAC:pk _max ;+NP
NS
× :VOUT + VRECT; = 373 + 34
6 × 19.95 = 486 V
V
RECT:rev ; = lNS
NP
× V
AC:pk_max ;p + :V
OUT + V
RECT; = 6
34 × 373 + 19.95 = 85.8 V
VCS (slope ) = 50% × dBULK:min ; × RCS × nNS
NP × :VOUT + VRECT;
LPRI r= 0.5 × 0.635 × 0.2 × F34 6
¤ × 19.95
txrJG = 27.6 mV/Js
dBULK:min ; =
NP
NS
× :V
OUT + V
RECT;
FV
BULK:min ; + NP
NS
× :V
OUT + V
RECT;G =
34 6 × :19.95;¤
:65 + 34 6 × :19.95;¤; = 63.5%
62
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9.2.4.8 Slope Compensation Verification
After choosing the current sense resistor, transformer inductance and transformer turns ratio, verify the required
slope compensation against the fixed internal slope compensation. The worst case slope compensation
requirement always occurs at the highest duty cycle operating point (at minimum bulk voltage level).
For stability, the slope compensation should be at least 50% of the difference between the inductor up-slope and
down-slope. [reference Bob Mammano TI Power Supply Design Seminar paper, 2001, SLUP173]. For a flyback
converter, the difference in slopes in CCM is equal the operating duty cycle multiplied by the inductor current
down-slope value. For example, for 50% dBULK(min) at minimum bulk capacitor voltage, the required slope
compensation ramp is 25% of the inductor current down-slope.
As listed in Table 7, the specified peak-load transient is 130 W for 2 ms. In a worst case, peak transient timing
with respect to the AC phase, the VBULK minimum level dips to 65 V. This corresponds to a duty cycle of
approximately 63.5% according to Equation 50.
(50)
The required slope compensation ramp is calculated at 63.5% duty cycle.
(51)
This value is within the 30 mV/μs of internal slope compensation provided by the controller.
9.2.4.9 Power MOSFET and Output Rectifier Selection
The initial design target proposed the use of a 100-V Schottky rectifier. The secondary-side reverse voltage
stress can be verified using the final transformer design sh own in Equation 52.
(52)
The value derived from Equation 52 is close to the original design target of 85 V.
For 65-W load, the average DC output current is 3.35 A for 19.5-V output. However, to reduce losses, a much
higher current rated diode is typically used, to yield a much lower forward voltage drop VRECT. As shown in
Figure 44, a 30-A rated diode D7 is used in this case, with a forward drop of approximately 0.45 V at 3.5 A,
100°C.
For the primary-side MOSFET, the peak voltage stress can be estimated using Equation 53.
(53)
An allowance of at least 100 V must be added to this figure to account for the leakage inductance spike at turn-
off. This voltage spike depends on the transformer implementation and the amount of leakage inductance, as
well as the specific design of the snubber. A more aggressive snubber may reduce the voltage spike, but at the
expense of higher losses in the snubber. A voltage rating of at least 600 V is recommended for the power
MOSFET to allow for leakage.
The MOSFET rms current at low line, rated load, can be estimated using Equation 54.
(54)
As can be seen in Figure 44, the chosen MOSFET Q1 is a 13-A, 600-V device.
IOUT:lim ;=
1
RCS
×
NP
NS
×
KCC1
KCC2 + V
OUT × NP
NS
=
1
0.2 ×
34
6 ×
44.5
69.5 + @19.5 × 34
6A
= 7.0 A
ICAP:rms ;=
ã
3
3
3
3
3
3
3
3
3
3
3
3
É
È
È
È
ÇV
CS:bcm ;
RCS
×
NP
NS
× ªV
BULK:min ;
3 × mV
BULK:min ; + FNP
NS
× :V
OUT + V
RECT ;Gq
Ì
Ë
Ë
Ë
Ê2
FIOUT
2
63
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,
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,
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9.2.4.10 Output Capacitor Selection
Select the output capacitor value on the basis of one of the following, depending on which one is the limiting
factor:
Required ripple current rating to absorb the high secondary-side peak current
Required esr to achieve a target peak-peak ripple voltage
Required holdup capacitance to achieve target minimum output voltage for a specified load transient from no
load when the device is switching at fSW(min)
For flyback converters, ripple current rating often dictates the output capacitance value. The required ripple
current rating can be calculated from Equation 55.
(55)
At rated 65-W load, ICAP(rms) = 5.9 ARMS. Capacitors C11 and C13 in Figure 43 are chosen to meet this ripple
requirement, (each capacitor has a 2.5-A minimum rating at 105°C). Total output capacitance is 1360 μF.
9.2.4.11 Calculation of CC Mode Limit Point
Calculate the expected output constant-current (CC) limit point from Equation 20. As previously noted, KCC1 is
44.5 and KCC1 is 69.5. Thus, IOUT(lim) in this case is approximately calculated in Equation 56.
(56)
CVDD RCX × FV
AC:pk ;FV
SELV
V
DD:start _min ;FV
DD:reset _max ;G = 330 nF × l373 F60
13 F6.5 p = 15.9 JF
CVDD=:8m × 3m; + :8m + 60 k × 30n; × @19.5 × suxrJ
7.0 F 3.35 A × @8.5
12.6A
:13.0 F 8.5; LsxärJF
CVDD =
: 8m × 3m;+k8m + 60 k × Qg:PKP ;o × lVOUT × COUT
IOUT:HEI ;FIO:I=T ;p × l8.5
VBIAS:JKI ;p
:13.0 F8.5;
CVDD=kIDD:run ; × tSTART:del ;o + kIDD:run ; + FSW:nom ; × Qg:tot ;o × lVOUT × COUT
IOUT:lim ;FIO:max ;p × lVDD:stop _max ;
VBIAS:nom ;p
cVDD:start _min ;FVDD:stop _max ;g
64
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,
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9.2.4.12 VDD Capacitor Selection
Size the VDD capacitor to supply sufficient IDD(run) current to the device during initial start-up, and also during the
charging phase of the main output capacitors. During the charging phase the bias winding on the transformer
must supply the bias power. When VDD reaches the VDD(start) threshold, the device consumes IDD(run) for tSTART(del)
before the PWM switching commences. Thereafter, the bias current is the device current plus the MOSFET gate
current. The VDD capacitor must support this higher level of current until the output is sufficiently charged that
the bias winding rail has increased above the VDD(stop) level.
Calculate the required bias capacitance from the total bias charge associated with the device run current during
the tSTART(del) phase, plus the device run current during the output charge phase, plus the primary MOSFET gate
charge current during the output charge phase. The time taken for the output charge phase to reach a sufficient
level to supply the bias can be calculated from the size of the output capacitor, target output regulation voltage,
and the difference between the available CC mode current limit and the maximum load current (assuming that
the output capacitor has to be charged whilst also supplying full rated load current). Assume that the MOSFET is
switched at 60 kHz throughout the charging phase.
Combining these into one equation, the required VDD capacitor can be calculated as shown in Equation 57.
(57)
This can be re-written with the explicit device values substituted:
(58)
For this EVM design, the MOSFET Qg(tot) is 30 nC, VBIAS(nom) is 12.6 V. IO(max) is 3.35 A, so this equates to:
(59)
Choose the next higher standard value, 22 μF.
Verify that the bias capacitance is sufficient to absorb all the X-capacitor energy when it has to be discharged,
per Equation 3. From Figure 44, the value of X-capacitor is 330 nF.
(60)
RLED = VOUT2FVOUT × VLED
2 × P:preload _min ;
= 19.52F19.5 × 1.8
2 × 19.23m = 8.97 k3
PPRELOAD:min ; = 0.5 × LPRI×lV
CS:min ;
RCS p2
× fSW:min ; = 0.5 × 260 JH × l0.172
0.2 p2
× 200 = 19.23 mW
RB = RA
LkV
OUT × k1F%LLK:sec _bias ;o + VRECTo × @NBNS
WA
V
OUT:ref ;F1M=22.6 k3
l:19.5 × :1F0.04; + 0.45; × :4 6
¤;
7.50 F1p = 32.10 k3
RA = RP × lNB
NPp × KLINE = 3.9 k3× l4
34p × 49.25 = 22.597 k3
%LLK:sec _bias ;=LSEC:bias _short ;
LSEC:bias _open ;
65
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9.2.4.13 Magnetic Sense Resistor Network Selection
The required values for the magnetic sense divider network are calculated from Equation 11 and Equation 12.
For the RM10/I transformer used in the PWR572 EVM, the secondary-side to bias leakage inductance was
measured and found to be approximately 4%. This figure can be reasonably estimated as the ratio of the
inductance value measured across the secondary-side pins with the bias pins shorted together (primary winding
should remain open-circuit), to the inductance value measured across the secondary-side pins with all other
windings open:
(61)
RAis calculated as shown in Equation 62.
(62)
The nearest standard E96 value 22.6 kΩis selected. RBmay then be calculated to set VOUT at 19.5 V.
(63)
The nearest E96 value is 32.4 kΩ, which could be used, but results in some set-point regulation error. As shown
in Figure 44, the setpoint may be fine-tuned by using two parallel resistors for RB. In this case use values of 39
kΩand 180 kΩ, to give a net equivalent of 32.05 kΩ, very close to the target value in Equation 63.
Note that the pull-up diode to DRV pin should be a standard switching signal diode such as BAS21 or similar.
The reverse recovery of the diode should be 100 ns or less. A slow-recovery diode clamps the VSENSE pin low
for an initial portion of the flyback interval, and may impair or prevent the ability to take a valid output voltage
sample.
9.2.4.14 Output LED Pre-Load Resistor Calculation
As shown in Figure 44, the output power good LED1 and series resistor R18 form an output pre-load or minimum
load. This pre-load is necessary in order to maintain regulation at no load, or when the power converter output is
disconnected from the load system. Magnetic regulation relies on sensing the output voltage during switching
cycles, so it is necessary to maintain a certain minimum switching frequency fSW(min) in order to continue sensing
the output voltage. However, generating switching cycles at fSW(min) transfers energy to the output, which requires
some load on the secondary-side to absorb this energy and prevent the output capacitors from being charged out
of regulation. The minimum energy transferred at fSW(min) depends on the choice of magnetizing inductance LPRI
and current sense resistor RCS.
(64)
In order to ensure that the control loop operates at a frequency above the minimum switching frequency, fSW(min)
(to ensure that the loop has adjustment range up/down as required to maintain regulation), the recommended
minimum pre-load is at least twice the value calculated in Equation 64.
The required value of R18 can then be calculated, assuming a forward voltage drop of 1.8 V for the LED:
(65)
Use the next lower E24 value of 8.2 kΩ. For a design without an LED, a pre-load resistor of similar value is still
required across the output voltage.
(NB/NS) x RWAKE
(NB/NP)2 x LP
RT
RB
VSENSE
+
±(NB/NP)2 x CP
ZLC(bias)
(NB/NS) x VOUT
VOUT
RWAKE
VBULK
LP
CP
NPNS
NBRT
RB
VSENSE
66
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,
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9.2.5 External Wake Pulse Calculation at VSENSE Pin (UCC28633 Only)
The typical application circuit of Figure 39 may be redrawn as a simplified equivalent circuit as shown in
Figure 45. In this equivalent circuit, the capacitor CPis the total parasitic capacitance (MOSFET Coss, transformer
capacitance, etc), and resistance RWAKE is the effective internal resistance of the UCC24650 WAKE pin to GND
pin when the internal WAKE pull-down is active (see UCC24650 detailed datasheet specifications).
If all the elements on the primary and secondary of the transformer are referred to the bias winding, this can be
further simplified as in Figure 46.
Figure 45. Simplified Equivalent Circuit of Wake Event with UCC24650
Figure 46. Bias-Referred Simplified Equivalent Circuit of Wake Event with UCC24650
V
RZ
Z
N
N
V
RR R
V
biasW AKEbiasLC
biasLC
S
B
W AKEOUT
BA
B
SENSE pkWAKE
743.0
1789.19 9.19
6
4
%975.19
05.326.22 05.32
1%
)(
¸
¹
·
¨
©
§
u
¸
¹
·
¨
©
§uuu
¸
¹
·
¨
©
§
¸
¸
¹
·
¨
¨
©
§
u
¸
¸
¹
·
¨
¨
©
§u'uu
¸
¸
¹
·
¨
¨
©
§
<.%(>E=O )=¨.2
%2
×l0$
02p2
=¨260ä
126L×l4
34p2
= 19.9
:
%2=l6
NAO
2èp2
×
1
.2
=l1.138ä
2èp2
×
1
260ä= 126 L(
%2=l6
NAO
2èp2
×
1
.2
8
5'05'_9#-' (LG )=l4$
4#+4$p×l8
176 × (1 F¿9#-'%) × 0$
0
5p×F<.%(>E=O )
<.%(>E=O )+49#-' (>E=O )G
49#-' (>E=O )=49#-' ×l0
$
0
5p2
<.%(>E=O )=¨.2
%2
×l0
$
0
2p2
67
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,
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Thus, knowing LPand CP, the power stage impedance ZLC(bias) (reflected to the bias winding) may be calculated
from Equation 66, and the effective wake resistance can be referred to the bias winding using Equation 67. The
wake pulse amplitude can be calculated from Equation 68. If CPis not known, it can be measured by observing
the resonant ring period at the primary drain node, TRES, and calculating CPfrom Equation 69. Worst case values
should be used to estimate the worst case minimum wake pulse amplitude at the VSENSE pin. It should also be
noted that any filter cap on the VSENSE pin (including internal parasitic pin capacitance) adds an RC filter in
conjunction with the Thevenin resistance of the VSENSE divider, RT, RB; this delays and further attenuate the
wake pulse amplitude. Additionally, the internal wake comparator requires some over-drive to trip, and exhibits
propagation delay that depends on the amount of overdrive. So some margin should be allowed in the wake
pulse amplitude to ensure that the minimum wake pulse can adequately overdrive the internal wake comparator.
A margin of at least 20% over the threshold VSENSE(wake) is recommended.
(66)
(67)
(68)
(69)
If the worst case wake pulse amplitude is too low, then the UCC24650 WAKE output can be augmented with an
external PNP circuit Q1, R1 and R2, as shown in Figure 40. This circuit reduces the effective wake resistance to
ground, so that a larger proportion of the output voltage appears across the transformer secondary pins when the
UCC24650 WAKE activates.
Using the UCC28630EVM-572, (TI Literature Number SLUUAX9) circuit parameters from Figure 44, the nominal
wake pulse amplitude at the VSENSE pin can be estimated. Of course, the rectifying diode D7 in Figure 44
would need to be relocated to return end of the secondary winding (pins 10, 11) to allow UCC24650 to be
deployed.
From observation of the DCM ringing period, the period TRES was found to be 1.138 μs. From Equation 69, CPis
estimated:
(70)
From Equation 66, the power circuit impedance is:
(71)
The WAKE pin resistance RWAKE can be determined form the UCC24650 datasheet; for now a nominal value of
400 Ωis assumed. Referred to the bias winding (scaled by (NB/NS)2), this becomes 178 Ω. Similarly ΔWAKE% can
be determined from the UCC24650 datasheet; for now, a value of 97% is assumed. From Equation 68, the wake
pulse amplitude can be calculated:
(72)
In this case, the VSENSE wake pulse amplitude would be insufficient to trip the internal wake comparator. If the
power stage had higher LP, or lower CP, a larger wake pulse would be produced.
68
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,
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Alternatively, the effective wake resistance RWAKE may be reduced by adding the PNP circuit per Figure 40. This
has been verified using Q1 = FMMTA92 PNP transistor, R1= 100 Ωand R2 = 2.2 kΩ. A wake pulse amplitude of
almost 2 VPK was produced at the VSENSE pin, giving generous margin to the internal threshold VSENSE(wake).
The observed waveforms are shown in Figure 47 for a worst case 0% to 100% (65 W) load transient (where the
PWM is at FMIN). The PWM is re-activated when VOUT has dropped by ~3%, rather waiting for the next timed
wake-up (~5 ms later).
Figure 48 shows a zoomed waveform of the wake pulsing ringing as measured on the bias winding. It can be
seen that the peak level is approximately 3 VPK, which would produce a pulse of approximately 1.8 V at the
VSENSE pin (scaled by VSENSE divider resistors RTand RB). As noted in Test and Debug Recommendations,
the VSENSE pin should never be directly probed, doing so affects the regulation setpoint.
Figure 47. Observed Output Voltage (Ch3) and Bias Winding (Ch4)
(showing wake event generated by UCC24650)
Figure 48. Zoom In of Wake-Pulse Ringing
(observed across bias winding (ChB) generated by UCC24650)
69
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9.2.6 Energy Star Average Efficiency and Standby Power
Table 8 summarize the standby power, and Table 9 summarizes the average efficiency performance of the
UCC28630EVM-572, (TI Literature Number SLUUAX9).
Table 8. Standby Power Performance
STANDBY POWER
115 VAC (mW) 230 VAC (mW)
57 60
Table 9. Average Efficiency Performance
AVERAGE EFFICIENCY (INCLUDING OUTPUT 76-mΩCABLE DROP)
LOAD LEVEL (%) 115 VAC (%) 230 VAC (%)
25 (16.25 W) 89.44 89.26
50 (32.5 W) 88.98 89.38
75 (48.75 W) 88.24 89.10
100 (65 W) 87.59 88.73
Average 88.6 89.1
70
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9.2.7 Application Performance Plots
Figure 49. Start-Up from 90-VAC, 3.35-A CC Load Figure 50. Start-Up from 230-VAC, 3.35-A CC Load
Figure 51. Output Rise-Time, 90-VAC, 3.35-A CC Load Figure 52. Output Rise-Time, 230-VAC, 3.35 A CC Load
10
11
12
13
14
15
16
17
18
19
20
0246810
Output Voltage (V)
Output Current (A)
90 V/50 Hz
100 V/60 Hz
120 V/60 Hz
143 V/63 Hz
200 V/47 Hz
230 V/50 Hz
269 V/63 Hz
C021
19
19.1
19.2
19.3
19.4
19.5
19.6
19.7
19.8
19.9
20
0 10 20 30 40 50 60 70
Output Voltage (V)
Output Power (W)
90 V/50 Hz
100 V/60 Hz
120 V/60 Hz
143 V/63 Hz
200 V/47 Hz
230 V/50 Hz
269 V/63 Hz
C019
18.6
18.8
19
19.2
19.4
19.6
19.8
20
0 10 20 30 40 50 60 70
Output Voltage (V)
Output Power (W)
90 V/50 Hz
100 V/60 Hz
120 V/60 Hz
143 V/63 Hz
200 V/47 Hz
230 V/50 Hz
269 V/63 Hz
C020
80
81
82
83
84
85
86
87
88
89
90
0 10 20 30 40 50 60 70
Efficiency (%)
Load Power (W)
115 VAC
230 VAC
C017
65
70
75
80
85
90
0 1 2 3 4 5 6 7 8
Efficiency (%)
Load Power (W)
115 VAC
230 VAC
C018
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Figure 53. Efficiency vs. Load/Line
(cable drop included) Figure 54. Zoom Light-Load Efficiency vs. Load/Line
(cable drop included)
Figure 55. Output Voltage Regulation vs. Line/Load
(without cable drop) Figure 56. Output Voltage Regulation vs. Line/Load
(with cable drop included)
Figure 57. CC Mode Regulation vs. Line
Figure 58. Transient Step 5% to 50% Load, 115 VAC
±360
±330
±300
±270
±240
±210
±180
±150
±120
±90
±60
±30
0
±25
±20
±15
±10
±5
0
5
10
15
20
25
30
35
10 100 1000
Phase(ƒ)
Gain (dB)
Frequency (Hz)
Gain
Phase
C022
±360
±330
±300
±270
±240
±210
±180
±150
±120
±90
±60
±30
0
±40
±30
±20
±10
0
10
20
30
40
50
10 100 1000
Phase(ƒ)
Gain (dB)
Frequency (Hz)
Gain
Phase
C023
72
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Figure 59. Transient Step 50% to 100% Load, 115 VAC Figure 60. Transient Step 10% to 90% Load, 115 VAC
Figure 61. Measured Control Loop Gain/Phase at 300 VDC,
Full Load 3.35 A Figure 62. Measured Control Loop Gain/Phase at 300 VDC,
Light Load 0.2 A
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9.3 Dos and Don'ts
9.3.1 Test and Debug Recommendations
One important precaution must be noted during test and debug. Do not probe the VSENSE pin with an
oscilloscope probe, meter or differential probe. Doing so adds excessive capacitance to the pin, delaying the pin
rise-time, and causing the regulated system output voltage to increase.
10 Power Supply Recommendations
The VDD power pin for the device requires the placement of low-esr noise-decoupling capacitance as directly as
possible from the VDD pin to the GND pin. Ceramic capacitors with stable dielectric characteristics over
temperature are recommended, such as X7R or better. Depending on the operating temperature range of the
application, X5R may be acceptable, but the drop in capacitance value at high temperature and with applied DC-
bias may not be tolerable. Avoid dielectrics with poor temperature-stability. (such Y5V, Z5U)
The recommended decoupling capacitors are a 1-μF 1206-sized 50-V X7R capacitor, ideally with (but not
essential) a second smaller parallel 100-nF 0603-sized 50-V X7R capacitor. Higher voltage rating parts can also
be used. The use of 25-V rated parts is not recommended, due to the reduction in effective capacitance value
with applied DC bias.
In parallel with the ceramic noise-decoupling capacitor(s), a larger-capacitance energy storage capacitor is also
required, per Equation 58. This energy-storage capacitor does not require low esr, and does not necessarily
need to be located close to the device.
74
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11 Layout
11.1 Layout Guidelines
11.1.1 HV Pin
This pin is connected to the rectified AC input, and as such requires appropriate separation to other PCB
traces to meet the application requirements for functional isolation;
This pin must have 200 kΩof external resistance to allow the line voltage to be sensed for the X-capacitor
discharge block. At least two series resistors should be used to reduce the voltage across the pins of each
resistor, with each resistor rated for at least 200 V;
The connection to the resistors that feed the HV pin should have separate dedicated rectifying diodes from
the AC input lines, to avoid the DC filtering that the bulk capacitor provides after the main diode bridge; the
lower section of the main diode bridge can be shared by the device and the power stage;
A filtering or noise-decoupling capacitor is not recommended, such a capacitor will degrade the X-capacitor
sampling ability to distinguish AC from DC input.
11.1.2 VDD Pin
A 1-µF ceramic decoupling capacitor is recommended, placed as close as possible between the VDD pin and
GND, tracked directly to both pins.
11.1.3 VSENSE Pin
The tracking and layout of the VSENSE pin and connecting components is critical to minimizing noise pick-up
and interference in the magnetic sensing block. (See Figure 63 for suggested component placement and
tracking). Reduce the total surface area of traces on the VSENSE net to a minimum.
Because the resistance values of RAand RBare relatively high to minimize power dissipation, the high
impedance makes the VSENSE pin potentially noise-sensitive. To minimize noise pick-up, locate resistors RA
and RBas close as possible to the VSENSE pin, with RBin particular placed as directly as possible between
VSENSE and GND pins;
Depending on layout, a small noise filter capacitor may be useful on the VSENSE pin, such as C15 shown in
Figure 44. Connect this capacitor as directly as possible between the VSENSE and GND pins. Choose the
value of this capacitor as small as possible, and no greater than 10 pF. A larger value significantly delays the
voltage rise-time at the pin, and affects the regulation set-point;
In case of possible board faults that can pull the VSENSE pin below GND (such as R7 shorted), in order to
protect the pin and limit possible negative current out of the pin, a series resistor R4 (as shown in Figure 44)
and clamping diode from GND are recommended. Maintain the value of R4 between 100 Ωand 500 Ω. A
larger value may affect regulation and line sense accuracy.
For correct line sense operation, the switched pull-up R10 and D4 must be added. The value of R10 must be
3.9 kΩto match the internal device gain. The switched pull-up diode and the GND clamping diode can be
combined into a dual-diode common-cathode package, such as D4 as shown in Figure 44.
11.1.4 CS Pin
A small, external filter capacitor is recommended on the CS pin. Track the filter capacitor as directly as
possible from the CS to GND pin.
Referring to Figure 44, a series resistor such as R5 is typically connected between the current sensing
resistor R16 and the CS pin to form an R-C filter. A filter time constant between 100 ns and 200 ns is
recommended. If the filter time constant is made too large, the filtering causes the transformer peak current to
exceed the control loop demand level, which affects regulation and standby power. Place resistor R5 as close
as possible to the CS pin.
Reduce the total surface area of traces on the CS net to a minimum.
RA
RB1
~100 Q
To Bias
winding
To DRV
pin
3.9 lQ
Jumper/
link
To CS
resistor
VDD
DRV
HVVSENSE
SD
GND
1 µF
100 nF
G10 pF
G120 pF CS
RB2
UCC28630
75
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
www.ti.com
SLUSBW3D MARCH 2014REVISED DECEMBER 2017
Product Folder Links: UCC28630 UCC28631 UCC28632 UCC28633 UCC28634
Submit Documentation FeedbackCopyright © 2014–2017, Texas Instruments Incorporated
Layout Guidelines (continued)
11.1.5 SD Pin
Referring to Figure 44, the SD pin is connected to a temperature-sensing NTC RT1 in series with an adjust
resistor R6. The NTC can be tracked to the required hot-spot location, or it can be wired with flying leads to
the required hotspot.
Track the RT1 return to GND as directly as possible back to the GND pin of the device. RT1 should not be
connected to a power GND track or plane, in order to minimize error in the trip level.
The device internally filters the SD pin, so an external filter capacitor is not usually required. If the application
design requires an external capacitor, limit the value to 1 nF maximum.
11.1.6 DRV Pin
The DRV pin has high internal sink/source current capability. An external gate resistor is recommended. The
value depends on the choice of power MOSFET, efficiency and EMI considerations.
As shown in Figure 44 an anti-parallel path formed by D5 and R13 are placed across the gate resistor R11 to
allow turn-on and turn-off of the MOSFET to be independently adjusted.
A pull-down resistor (such as R15 in this example) on the gate of the external MOSFET is recommended to
prevent the MOSFET gate from floating on if there is an open circuit error in the gate drive path. The value of
R15 also affects the overload timer settings, so carefully choose the value of R15 according to Table 1.
Ensure that the noisy gate drive traces are routed away from the sensitive VSENSE pin and CS pin traces.
11.1.7 GND Pin
Connect decoupling and noise filter capacitors, as well as sensing resistors directly to the GND pin in a star-
point fashion, ensuring that the current-carrying power tracks (such as the gate drive return) are track
separately to avoid noise and ground-drops that could affect the analogue signal integrity.
11.2 Layout Example
Figure 63. Recommended PCB Layout for Single-Sided Assembly
76
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
SLUSBW3D MARCH 2014REVISED DECEMBER 2017
www.ti.com
Product Folder Links: UCC28630 UCC28631 UCC28632 UCC28633 UCC28634
Submit Documentation Feedback Copyright © 2014–2017, Texas Instruments Incorporated
12 Device and Documentation Support
12.1 Device Support
12.1.1 Development Support
12.1.1.1 Custom Design With WEBENCH® Tools
Click here to create a custom design using the UCC2863x device with the WEBENCH® Power Designer.
1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements.
2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.
3. Compare the generated design with other possible solutions from Texas Instruments.
The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time
pricing and component availability.
In most cases, these actions are available:
Run electrical simulations to see important waveforms and circuit performance
Run thermal simulations to understand board thermal performance
Export customized schematic and layout into popular CAD formats
Print PDF reports for the design, and share the design with colleagues
Get more information about WEBENCH tools at www.ti.com/WEBENCH.
12.2 Documentation Support
12.2.1 Related Documentation
UCC28630EVM-572, 65-W Nominal, 130-W Peak, Primary-Side Regulated Adapter Module (Texas Instruments
Literature Number SLUSAX9)
12.2.1.1 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 10. Related Links
PARTS PRODUCT FOLDER SAMPLE & BUY TECHNICAL
DOCUMENTS TOOLS &
SOFTWARE SUPPORT &
COMMUNITY
UCC28630 Click here Click here Click here Click here Click here
UCC28631 Click here Click here Click here Click here Click here
UCC28632 Click here Click here Click here Click here Click here
UCC28633 Click here Click here Click here Click here Click here
12.3 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
12.4 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
77
UCC28630
,
UCC28631
UCC28632
,
UCC28633
,
UCC28634
www.ti.com
SLUSBW3D MARCH 2014REVISED DECEMBER 2017
Product Folder Links: UCC28630 UCC28631 UCC28632 UCC28633 UCC28634
Submit Documentation FeedbackCopyright © 2014–2017, Texas Instruments Incorporated
Community Resources (continued)
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
12.5 Trademarks
E2E is a trademark of Texas Instruments.
WEBENCH is a registered trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
12.6 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
12.7 Glossary
SLYZ022 TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical packaging and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
PACKAGE OPTION ADDENDUM
www.ti.com 18-Jan-2018
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
UCC28630D ACTIVE SOIC D 7 75 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 U28630
UCC28630DR ACTIVE SOIC D 7 2500 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 U28630
UCC28631D ACTIVE SOIC D 7 75 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 U28631
UCC28631DR ACTIVE SOIC D 7 2500 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 U28631
UCC28632D ACTIVE SOIC D 7 75 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 U28632
UCC28632DR ACTIVE SOIC D 7 2500 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 U28632
UCC28633D ACTIVE SOIC D 7 75 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 U28633
UCC28633DR ACTIVE SOIC D 7 2500 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 U28633
UCC28634D ACTIVE SOIC D 7 75 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 U28634
UCC28634DR ACTIVE SOIC D 7 2500 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 U28634
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
PACKAGE OPTION ADDENDUM
www.ti.com 18-Jan-2018
Addendum-Page 2
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
UCC28630DR SOIC D 7 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1
UCC28631DR SOIC D 7 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1
UCC28633DR SOIC D 7 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1
UCC28634DR SOIC D 7 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 9-Jan-2018
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
UCC28630DR SOIC D 7 2500 367.0 367.0 35.0
UCC28631DR SOIC D 7 2500 367.0 367.0 35.0
UCC28633DR SOIC D 7 2500 367.0 367.0 35.0
UCC28634DR SOIC D 7 2500 367.0 367.0 35.0
PACKAGE MATERIALS INFORMATION
www.ti.com 9-Jan-2018
Pack Materials-Page 2
www.ti.com
PACKAGE OUTLINE
C
.228-.244 TYP
[5.80-6.19]
.069 MAX
[1.75]
.100
[2.54]
7X .012-.020
[0.31-0.51]
2X
.150
[3.81]
.005-.010 TYP
[0.13-0.25]
0 - 8 .004-.010
[0.11-0.25]
.010
[0.25]
.016-.050
[0.41-1.27]
4X .050
[1.27]
A
.189-.197
[4.81-5.00]
NOTE 3
B .150-.157
[3.81-3.98]
NOTE 4
(.041)
[1.04]
SOIC - 1.75 mm max heightD0007A
SMALL OUTLINE INTEGRATED CIRCUIT
4220728/A 01/2018
NOTES:
1. Linear dimensions are in inches [millimeters]. Dimensions in parenthesis are for reference only. Controlling dimensions are in inches.
Dimensioning and tolerancing per ASME Y14.5M.
2. This drawing is subject to change without notice.
3. This dimension does not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, or gate burrs shall not
exceed .006 [0.15] per side.
4. This dimension does not include interlead flash.
5. Reference JEDEC registration MS-012, variation AA.
18
.010 [0.25] C A B
5
4
PIN 1 ID AREA
SEATING PLANE
.004 [0.1] C
SEE DETAIL A
DETAIL A
TYPICAL
SCALE 2.800
www.ti.com
EXAMPLE BOARD LAYOUT
.0028 MAX
[0.07]
ALL AROUND
.0028 MIN
[0.07]
ALL AROUND
(.213)
[5.4]
4X (.050 )
[1.27]
7X (.061 )
[1.55]
7X (.024)
[0.6] (.100 )
[2.54]
SOIC - 1.75 mm max heightD0007A
SMALL OUTLINE INTEGRATED CIRCUIT
4220728/A 01/2018
NOTES: (continued)
6. Publication IPC-7351 may have alternate designs.
7. Solder mask tolerances between and around signal pads can vary based on board fabrication site.
METAL SOLDER MASK
OPENING
NON SOLDER MASK
DEFINED
SOLDER MASK DETAILS
EXPOSED
METAL
OPENING
SOLDER MASK METAL UNDER
SOLDER MASK
SOLDER MASK
DEFINED
EXPOSED
METAL
LAND PATTERN EXAMPLE
EXPOSED METAL SHOWN
SCALE:8X
SYMM
1
45
8
SEE
DETAILS
SYMM
www.ti.com
EXAMPLE STENCIL DESIGN
7X (.061 )
[1.55]
7X (.024)
[0.6]
4X (.050 )
[1.27] (.213)
[5.4]
(.100 )
[2.54]
SOIC - 1.75 mm max heightD0007A
SMALL OUTLINE INTEGRATED CIRCUIT
4220728/A 01/2018
NOTES: (continued)
8. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
9. Board assembly site may have different recommendations for stencil design.
SOLDER PASTE EXAMPLE
BASED ON .005 INCH [0.125 MM] THICK STENCIL
SCALE:8X
SYMM
SYMM
1
45
8
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Authorized Distributor
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