100
90
80
70
60
50 0.1 1
EFFICIENCY (%)
LOAD (A)
"X"
GND
FB
EN
VIN SW
VIN = 5V
C1
R3
D1
L1
R2
R1
C2 C3
VO = 3.3V @ 1.5A
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LM2831
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LM2831 High-Frequency 1.5-A Load — Step-Down DC-DC Regulator
1 Features 3 Description
The LM2831 regulator is a monolithic, high-
1• Space-Saving SOT-23 Package frequency, PWM step-down DC-DC converter in a 5-
• Input Voltage Range of 3 V to 5.5 V pin SOT-23 and a 6-Pin WSON package. The
• Output Voltage Range of 0.6 V to 4.5 V LM2831 provides all the active functions to provide
local DC-DC conversion with fast transient response
• 1.5-A Output Current and accurate regulation in the smallest possible PCB
• High Switching Frequencie area. With a minimum of external components, the
– 1.6 MHz (LM2831X) LM2831 is easy to use. The ability to drive 1.5-A
loads with an internal 130-mΩPMOS switch using
– 0.55 MHz (LM2831Y) state-of-the-art 0.5-µm BiCMOS technology results in
– 3 MHz (LM2831Z) the best power density available. The world-class
• 130-mΩPMOS Switch control circuitry allows on-times as low as 30 ns, thus
• 0.6-V, 2% Internal Voltage Reference supporting exceptionally high frequency conversion
over the entire 3 V to 5.5 V input operating range,
• Internal Soft Start down to the minimum output voltage of 0.6 V.
• Current Mode, PWM Operation Switching frequency is internally set to 550 kHz, 1.6
• Thermal Shutdown MHz, or 3 MHz, allowing the use of extremely small
surface mount inductors and chip capacitors. Even
• Overvoltage Protection though the operating frequency is high, efficiencies of
up to 93% are easy to achieve. External shutdown is
2 Applications included, featuring an ultra-low standby current of 30
• Local 5 V to Vcore Step-Down Converters nA. The LM2831 utilizes current-mode control and
internal compensation to provide high-performance
• Core Power in HDDs regulation over a wide range of operating conditions.
• Set-Top Boxes Additional features include internal soft-start circuitry
• USB Powered Devices to reduce inrush current, pulse-by-pulse current limit,
• DSL Modems thermal shutdown, and output overvoltage protection.
Device Information(1)
PART NUMBER PACKAGE BODY SIZE (NOM)
WSON (6) 3.00 mm × 3.00 mm
LM2831 SOT-23 (5) 1.60 mm × 2.90 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application Circuit Efficiency vs Load
1
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.
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
Table of Contents
7.4 Device Functional Modes........................................ 11
1 Features.................................................................. 18 Application and Implementation ........................ 12
2 Applications ........................................................... 18.1 Application Information............................................ 12
3 Description............................................................. 18.2 Typical Applications ............................................... 12
4 Revision History..................................................... 29 Power Supply Recommendations...................... 25
5 Pin Configuration and Functions......................... 310 Layout................................................................... 25
6 Specifications......................................................... 410.1 Layout Guidelines ................................................. 25
6.1 Absolute Maximum Ratings ...................................... 410.2 Layout Example .................................................... 29
6.2 ESD Ratings.............................................................. 411 Device and Documentation Support................. 30
6.3 Recommended Operating Conditions....................... 411.1 Device Support...................................................... 30
6.4 Thermal Information.................................................. 411.2 Documentation Support ........................................ 30
6.5 Electrical Characteristics........................................... 511.3 Community Resources.......................................... 30
6.6 Typical Characteristics.............................................. 611.4 Trademarks........................................................... 30
7 Detailed Description.............................................. 911.5 Electrostatic Discharge Caution............................ 30
7.1 Overview................................................................... 911.6 Glossary................................................................ 30
7.2 Functional Block Diagram......................................... 912 Mechanical, Packaging, and Orderable
7.3 Feature Description................................................... 9Information ........................................................... 30
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (April 2013) to Revision D Page
• Added ESD Ratings table, Feature Description section, Device Functional Modes,Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section. ................................................................................................ 1
Changes from Revision B (April 2013) to Revision C Page
• Changed layout of National Data Sheet to TI format ........................................................................................................... 24
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Product Folder Links: LM2831
VIN SW
2
1
3
5
4
EN FB
GND
1
2
34
6
5
EN
FB
SW
DAP VINA
VIND
GND
LM2831
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SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
5 Pin Configuration and Functions
NGG Package
6-Pins WSON
Top View
DBV Package
5-Pin SOT-23
Top View
Pin Functions
PIN I/O DESCRIPTION
NAME SOT-23 WSON
Enable control input. Logic high enables operation. Do not allow this pin to
EN 4 6 I float or be greater than VIN + 0.3 V, or VINA + 0.3 V for WSON.
FB 3 1 I Feedback pin. Connect to external resistor divider to set output voltage.
Signal and power ground pin. Place the bottom resistor of the feedback
GND 2 2 PWR network as close as possible to this pin.
SW 1 3 O Output switch. Connect to the inductor and catch diode.
VIN 5 — PWR Input supply voltage
VINA — 5 PWR Control circuitry supply voltage. Connect VINA to VIND on PC board.
VIND — 4 PWR Power input supply
Die Attach Connect to system ground for low thermal impedance, but it cannot be
— DAP PWR
Pad used as a primary GND connection.
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)(1)(2)
MIN MAX UNIT
VIN –0.5 7 V
FB Voltage –0.5 3 V
EN Voltage –0.5 7 V
SW Voltage –0.5 7 V
Junction Temperature(3) 150 °C
Soldering Information Infrared or Convection Reflow (15 sec) 220 °C
Storage Temperature, Tstg –65 150 °C
(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
(3) Thermal shutdown will occur if the junction temperature exceeds the maximum junction temperature of the device.
6.2 ESD Ratings VALUE UNIT
V(ESD) Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) ±2000 V
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted) MIN NOM MAX UNIT
VIN 3 5.5 V
Junction Temperature –40 125 °C
6.4 Thermal Information LM2831
THERMAL METRIC(1) SOT-23 (DBV WSON (NGG) UNIT
5 PINS 6 PINS
RθJA Junction-to-ambient thermal resistance(2) 163.4 54.9 °C/W
RθJC(top) Junction-to-case (top) thermal resistance(2) 114.4 50.8 °C/W
RθJB Junction-to-board thermal resistance 26.8 29.2 °C/W
ψJT Junction-to-top characterization parameter 12.4 0.6 °C/W
ψJB Junction-to-board characterization parameter 26.2 29.3 °C/W
RθJC(bot) Junction-to-case (bottom) thermal resistance N/A 9.2 °C/W
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
(2) Applies for packages soldered directly onto a 3” × 3” PC board with 2 oz. copper on 4 layers in still air.
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6.5 Electrical Characteristics
VIN = 5 V unless otherwise indicated under the Test Conditions column. Limits are for TJ= 25°C. Minimum and Maximum
limits are specified through test, design, or statistical correlation. Typical values represent the most likely parametric norm at
TJ= 25°C, and are provided for reference purposes only.
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
WSON and SOT-23 TJ= 25°C 0.600
VFB Feedback Voltage V
Package –40°C to 125°C 0.588 0.612
ΔVFB/VIN Feedback Voltage Line Regulation VIN = 3 V to 5 V 0.02 %/V
IBFeedback Input Bias Current TJ= 25°C 0.1 nA
–40°C to 125°C 100
VIN Rising TJ= 25°C 2.73 V
–40°C to 125°C 2.90
Undervoltage Lockout
UVLO VIN Falling TJ= 25°C 2.3 V
–40°C to 125°C 1.85
UVLO Hysteresis 0.43 V
LM2831-X TJ= 25°C 1.6
–40°C to 125°C 1.2 1.95
LM2831-Y TJ= 25°C 0.55
FSW Switching Frequency MHz
–40°C to 125°C 0.4 0.7
LM2831-Z TJ= 25°C 3
–40°C to 125°C 2.25 3.75
LM2831-X TJ= 25°C 94%
–40°C to 125°C 86%
LM2831-Y TJ= 25°C 96%
DMAX Maximum Duty Cycle –40°C to 125°C 90%
LM2831-Z TJ= 25°C 90%
–40°C to 125°C 82%
LM2831-X 5%
DMIN Minimum Duty Cycle LM2831-Y 2%
LM2831-Z 7%
WSON Package 150
RDS(ON) Switch On Resistance SOT-23 Package TJ= 25°C 130 mΩ
–40°C to 125°C 195
ICL Switch Current Limit VIN = 3.3 V TJ= 25°C 2.5 A
–40°C to 125°C 1.8
Shutdown Threshold Voltage –40°C to 125°C 0.4
VEN_TH V
Enable Threshold Voltage –40°C to 125°C 1.8
ISW Switch Leakage 100 nA
IEN Enable Pin Current Sink/Source 100 nA
LM2831X VFB = 0.55 TJ= 25°C 3.3
–40°C to 125°C 5
LM2831Y VFB = 0.55 TJ= 25°C 2.8
Quiescent Current (switching) mA
IQ–40°C to 125°C 4.5
LM2831Z VFB = 0.55 TJ= 25°C 4.3
–40°C to 125°C 6.5
Quiescent Current (shutdown) All Options VEN = 0 V 30 nA
TSD Thermal Shutdown Temperature 165 °C
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-45 -40 -10 20 50 80 110 125 130
TEMPERATURE (ºC)
OSCILLATOR FREQUENCY (MHz)
0.46
0.48
0.50
0.52
0.54
0.56
0.58
0.60
-45 -40 -10 20 50 80 110 125 130
TEMPERATURE (ºC)
OSCILLATOR FREQUENCY (MHz)
1.36
1.41
1.46
1.51
1.56
1.61
1.66
1.71
1.76
1.81
1.794
1.796
1.798
1.800
1.802
1.804
1.806
0.25 0.5 0.75 1 1.25 1.5
LOAD (A)
OUTPUT (V)
0
3.297
3.298
3.299
3.300
3.301
3.302
0 0.25 0.5 0.75 1 1.25 1.5
LOAD (A)
OUTPUT (V)
1.796
1.797
1.798
1.799
1.800
1.801
1.802
1.803
1.804
0 0.25 0.5 0.75 1 1.25 1.5
LOAD (A)
OUTPUT (V)
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
6.6 Typical Characteristics
All curves taken at VIN = 5 V with configuration in typical application circuit shown in Application Information section of this
datasheet. TJ= 25°C, unless otherwise specified.
VIN = 3.3 VO= 1.8 V VIN = 3.3 V VO= 1.8 V (All Options)
Figure 1. ηvs Load – X, Y, and Z Options Figure 2. Load Regulation
VIN = 5 V VO= 1.8 V (All Options) VIN = 5 V VO= 3.3 V (All Options)
Figure 3. Load Regulation Figure 4. Load Regulation
Figure 5. Oscillator Frequency vs Temperature – X Option Figure 6. Oscillator Frequency vs Temperature – Y Option
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-45 -40 -10 20 50 80 110 125 130
TEMPERATURE (ºC)
3.0
3.1
3.2
3.3
3.4
3.5
3.6
IQ (mA)
-45 -40 -10 20 50 80 110 125 130
TEMPERATURE (°C)
2.15
2.2
2.25
2.3
2.35
2.4
2.45
2.5
2.55
2.6
2.65
IQ (mA)
-45 -40 -10 20 50 80 110 125 130
TEMPERATURE (°C)
2100
2200
2300
2400
2500
2600
2700
2800
2900
CURRENT LIMIT (mA)
-45 -40 -10 20 50 80 110 125 130
TEMPERATURE (ºC)
OSCILLATOR FREQUENCY (MHz)
2.55
2.65
2.75
2.85
2.95
3.05
3.15
3.25
3.35
3.45
LM2831
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SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
Typical Characteristics (continued)
All curves taken at VIN = 5 V with configuration in typical application circuit shown in Application Information section of this
datasheet. TJ= 25°C, unless otherwise specified.
VIN = 3.3 V
Figure 7. Oscillator Frequency vs Temperature – Z Option Figure 8. Current Limit vs Temperature
Figure 9. RDSON vs Temperature (WSON Package) Figure 10. RDSON vs Temperature (SOT-23 Package)
Figure 12. LM2831Y IQ(Quiescent Current)
Figure 11. LM2831X IQ(Quiescent Current)
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-45 -40 -10 20 50 80 110 125 130
TEMPERATURE (ºC)
FEEBACK VOLTAGE (V)
0.590
0.595
0.600
0.605
0.610
-45 -40 -10 20 50 80 110 125 130
TEMPERATURE (ºC)
4.0
4.1
4.2
4.3
4.4
4.5
4.6
IQ (mA)
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
Typical Characteristics (continued)
All curves taken at VIN = 5 V with configuration in typical application circuit shown in Application Information section of this
datasheet. TJ= 25°C, unless otherwise specified.
VO= 1.8 V IO= 500 mA
Figure 14. Line Regulation
Figure 13. LM2831Z IQ(Quiescent Current)
VIN = 5 V VO= 1.2 V at 1 A
Figure 15. VFB vs Temperature Figure 16. Gain vs Frequency
VIN = 5 V VO= 1.2 V at 1 A
Figure 17. Phase Plot vs Frequency
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cv
+
-
+
-
S
R
R
Q
+
-
GND
FB
SW
VIN
EN
+
-
+
-
DRIVER
Artificial
Ramp
SHDN
Thermal
SHDN
OVP
1.6 MHz
CompInternal-
SENSE
I
LIMIT
I
LDOInternal-
STARTSOFT-
PFET
SENSE
I
ENABLE and UVLO
15.1 x REF
VControl Logic
VREF = 0.6V
LM2831
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SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
7 Detailed Description
7.1 Overview
The LM2831 device is a constant-frequency PWM buck regulator IC that delivers a 1.5-A load current. The
regulator has a preset switching frequency of 550 kHz, 1.6 MHz, or 3 MHz. This high-frequency allows the
LM2831 to operate with small surface mount capacitors and inductors, resulting in a DC-DC converter that
requires a minimum amount of board space. The LM2831 is internally compensated, so the device is simple to
use and requires few external components.
7.2 Functional Block Diagram
7.3 Feature Description
7.3.1 Theory of Operation
The LM2831 uses current-mode control to regulate the output voltage. The following operating description of the
LM2831 will refer to Functional Block Diagram and to the waveforms in Figure 18. The LM2831 supplies a
regulated output voltage by switching the internal PMOS control switch at constant-frequency and variable duty
cycle. A switching cycle begins at the falling edge of the reset pulse generated by the internal oscillator. When
this pulse goes low, the output control logic turns on the internal PMOS control switch. During this on-time, the
SW pin voltage (VSW) swings up to approximately VIN, and the inductor current (IL) increases with a linear slope.
ILis measured by the current sense amplifier, which generates an output proportional to the switch current. The
sense signal is summed with the regulator’s corrective ramp and compared to the error amplifier’s output, which
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0
0
VIN
VD
TON
t
t
Inductor
Current
D = TON/TSW
VSW
TOFF
TSW
IL
IPK
SW
Voltage
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
Feature Description (continued)
is proportional to the difference between the feedback voltage and VREF. When the PWM comparator output goes
high, the output switch turns off until the next switching cycle begins. During the switch off-time, inductor current
discharges through the Schottky catch diode, which forces the SW pin to swing below ground by the forward
voltage (VD) of the Schottky catch diode. The regulator loop adjusts the duty cycle (D) to maintain a constant
output voltage.
Figure 18. Typical Waveforms
7.3.2 Soft Start
This function forces VOUT to increase at a controlled rate during start up. During soft start, the error amplifier’s
reference voltage ramps from 0 V to its nominal value of 0.6 V in approximately 600 µs. This forces the regulator
output to ramp up in a controlled fashion, which helps reduce inrush current.
7.3.3 Output Overvoltage Protection
The overvoltage comparator compares the FB pin voltage to a voltage that is 15% higher than the internal
reference VREF. Once the FB pin voltage goes 15% above the internal reference, the internal PMOS control
switch is turned off, which allows the output voltage to decrease toward regulation.
7.3.4 Undervoltage Lockout
Undervoltage lockout (UVLO) prevents the LM2831 from operating until the input voltage exceeds 2.73 V
(typical). The UVLO threshold has approximately 430 mV of hysteresis, so the part will operate until VIN drops
below 2.3 V (typical). Hysteresis prevents the part from turning off during power up if VIN is non-monotonic.
7.3.5 Current Limit
The LM2831 uses cycle-by-cycle current limiting to protect the output switch. During each switching cycle, a
current limit comparator detects if the output switch current exceeds 2.5 A (typical), and turns off the switch until
the next switching cycle begins.
7.3.6 Thermal Shutdown
Thermal shutdown limits total power dissipation by turning off the output switch when the IC junction temperature
exceeds 165°C. After thermal shutdown occurs, the output switch doesn’t turn on until the junction temperature
drops to approximately 150°C.
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7.4 Device Functional Modes
The LM2831 has an enable pin (EN) control Input. A logic high enables device operation. Do not float this pin or
let this pin be greater than VIN + 0.3 V for the SOT package option, or VINA + 0.3 V for the WSON package
option.
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GND
FB
EN
VIN SW
VIN = 5V
C1
R3
D1
L1
LM2831
R2
R1
C2
VO = 1.2V @ 1.5A
LM2831
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8 Application 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.
8.1 Application Information
The LM2831 device will operate with input voltage range from 3 V to 5.5 V and provide a regulated output
voltage. This device is optimized for high-efficiency operation with minimum number of external components. For
component selection, see Detailed Design Procedure.
8.2 Typical Applications
8.2.1 LM2831X Design Example 1
Figure 19. LM2831X (1.6 MHz): VIN =5V,VO= 1.2 V at 1.5 A
8.2.1.1 Design Requirements
The device must be able to operate at any voltage within the recommended operating range. Load current must
be defined to properly size the inductor, input, and output capacitors. Inductor should be able to handle full
expected load current as well as the peak current generated during load transients and start up. Inrush current at
start-up will depend on the output capacitor selection. More details are provided in Detailed Design Procedure.
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IN OUT L
S
V V 2 i
L DT
-D
=
t
L
i'
OUT
I
S
T
S
DT
L
VOUT
L
- VOUT
VIN
OUT D
IN D SW
V V
D
V V V
+
=
+ -
OUT
IN
V
D
V
=
LM2831
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SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
Typical Applications (continued)
8.2.1.2 Detailed Design Procedure
Table 1. Bill of Materials
PART ID PART VALUE MANUFACTURER PART NUMBER
U1 1.5-A Buck Regulator TI LM2831X
C1, Input Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
C2, Output Cap 2x22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
D1, Catch Diode 0.3 VfSchottky 1.5 A, 30 VRTOSHIBA CRS08
L1 3.3 µH, 2.2 A TDK VLCF5020T-3R3N2R0-1
R2 15.0 kΩ, 1% Vishay CRCW08051502F
R1 15.0 kΩ, 1% Vishay CRCW08051502F
R3 100 kΩ, 1% Vishay CRCW08051003F
8.2.1.2.1 Inductor Selection
The duty cycle (D) can be approximated quickly using the ratio of output voltage (VO) to input voltage (VIN):
(1)
The catch diode (D1) forward voltage drop and the voltage drop across the internal PMOS must be included to
calculate a more accurate duty cycle. Calculate D by using the following formula:
(2)
VSW can be approximated by:
VSW = IOUT × RDSON (3)
The diode forward drop (VD) can range from 0.3 V to 0.7 V depending on the quality of the diode. The lower the
VD, the higher the operating efficiency of the converter. The inductor value determines the output ripple current.
Lower inductor values decrease the size of the inductor, but increase the output ripple current. An increase in the
inductor value will decrease the output ripple current.
One must ensure that the minimum current limit (1.8 A) is not exceeded, so the peak current in the inductor must
be calculated. The peak current (ILPK) in the inductor is calculated by:
ILPK = IOUT +ΔiL(4)
Figure 20. Inductor Current
(5)
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RMS _IN OUT
I I D(1 D)= ´ -
2
2
RMS _IN OUT
i
I D I (1 D) 3
é ù
D
- +
ê ú
ê ú
ë û
S
S
1
T
f
=
S
IN OUT
L
DT
L V V
2 i
æ ö
= ´ -
ç ÷
D
è ø
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
In general,
ΔiL= 0.1 × (IOUT)→0.2 × (IOUT) (6)
If ΔiL= 20% of 1.50 A, the peak current in the inductor will be 1.8 A. The minimum ensured current limit over all
operating conditions is 1.8 A. One can either reduce ΔiL, or make the engineering judgment that zero margin will
be safe enough. The typical current limit is 2.5 A.
The LM2831 operates at frequencies allowing the use of ceramic output capacitors without compromising
transient response. Ceramic capacitors allow higher inductor ripple without significantly increasing output ripple.
See the Output Capacitor section for more details on calculating output voltage ripple. Now that the ripple current
is determined, the inductance is calculated by:
(7)
Where:
(8)
When selecting an inductor, make sure that it is capable of supporting the peak output current without saturating.
Inductor saturation will result in a sudden reduction in inductance and prevent the regulator from operating
correctly. Because of the speed of the internal current limit, the peak current of the inductor need only be
specified for the required maximum output current. For example, if the designed maximum output current is 1 A
and the peak current is 1.25 A, then the inductor should be specified with a saturation current limit of > 1.25 A.
There is no need to specify the saturation or peak current of the inductor at the 2.5-A typical switch current limit.
The difference in inductor size is a factor of 5. Because of the operating frequency of the LM2831, ferrite based
inductors are preferred to minimize core losses. This presents little restriction since the variety of ferrite-based
inductors is huge. Lastly, inductors with lower series resistance (RDCR) will provide better operating efficiency. For
recommended inductors, see LM2831X Design Example 2 through LM2831X Buck Converter and Voltage
Double Circuit With LDO Follower Design Example 9.
8.2.1.2.2 Input Capacitor
An input capacitor is necessary to ensure that VIN does not drop excessively during switching transients. The
primary specifications of the input capacitor are capacitance, voltage, RMS current rating, and ESL (Equivalent
Series Inductance). The recommended input capacitance is 22 µF. The input voltage rating is specifically stated
by the capacitor manufacturer. Make sure to check any recommended deratings and also verify if there is any
significant change in capacitance at the operating input voltage and the operating temperature. The input
capacitor maximum RMS input current rating (IRMS-IN) must be greater than:
(9)
Neglecting inductor ripple simplifies the above equation to:
(10)
It can be shown from the above equation that maximum RMS capacitor current occurs when D = 0.5. Always
calculate the RMS at the point where the duty cycle D is closest to 0.5. The ESL of an input capacitor is usually
determined by the effective cross sectional area of the current path. A large leaded capacitor will have high ESL
and a 0805 ceramic chip capacitor will have very low ESL. At the operating frequencies of the LM2831, leaded
capacitors may have an ESL so large that the resulting impedance (2πfL) will be higher than that required to
provide stable operation. As a result, surface mount capacitors are strongly recommended.
Sanyo POSCAP, Tantalum or Niobium, Panasonic SP, and multilayer ceramic capacitors (MLCC) are all good
choices for both input and output capacitors and have very low ESL. For MLCCs it is recommended to use X7R
or X5R type capacitors due to their tolerance and temperature characteristics. Consult capacitor manufacturer
data sheets to see how rated capacitance varies over operating conditions.
14 Submit Documentation Feedback Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM2831
x R2
R1 = VREF
VOUT - 1
OUT L ESR
SW OUT
1
V I R
8 F C
æ ö
= D +
ç ÷
´ ´
è ø
LM2831
www.ti.com
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
8.2.1.2.3 Output Capacitor
The output capacitor is selected based upon the desired output ripple and transient response. The initial current
of a load transient is provided mainly by the output capacitor. The output ripple of the converter is:
(11)
When using MLCCs, the ESR is typically so low that the capacitive ripple may dominate. When this occurs, the
output ripple will be approximately sinusoidal and 90° phase shifted from the switching action. Given the
availability and quality of MLCCs and the expected output voltage of designs using the LM2831, there is really no
need to review any other capacitor technologies. Another benefit of ceramic capacitors is their ability to bypass
high frequency noise. A certain amount of switching edge noise will couple through parasitic capacitances in the
inductor to the output. A ceramic capacitor will bypass this noise while a tantalum will not. Since the output
capacitor is one of the two external components that control the stability of the regulator control loop, most
applications will require a minimum of 22 µF of output capacitance. Capacitance often, but not always, can be
increased significantly with little detriment to the regulator stability. Like the input capacitor, recommended
multilayer ceramic capacitors are X7R or X5R types.
8.2.1.2.4 Catch Diode
The catch diode (D1) conducts during the switch off-time. A Schottky diode is recommended for its fast switching
times and low forward voltage drop. The catch diode should be chosen so that its current rating is greater than:
ID1 = IOUT × (1-D) (12)
The reverse breakdown rating of the diode must be at least the maximum input voltage plus appropriate margin.
To improve efficiency, choose a Schottky diode with a low forward voltage drop.
8.2.1.2.5 Output Voltage
The output voltage is set using the following equation where R2 is connected between the FB pin and GND, and
R1 is connected between VOand the FB pin. A good value for R2 is 10 kΩ. When designing a unity gain
converter (Vo = 0.6 V), R1 should be from 0 Ωto 100 Ω, and R2 should be equal or greater than 10 kΩ.
(13)
VREF = 0.60 V (14)
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Product Folder Links: LM2831
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
8.2.1.3 Application Curves
See Typical Characteristics.
VIN = 5 V VO= 1.8 V and 3.3 V VIN = 5 V VO= 1.8 V and 3.3 V
Figure 21. ηvs Load – X Option Figure 22. ηvs Load – Y Option
VIN = 5 V VO= 1.8 V and 3.3 V
Figure 23. ηvs Load – Z Option
16 Submit Documentation Feedback Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM2831
GND
FB
EN
VIN SW
VIN = 5V
C1
R3
D1
L1
LM2831
R2
R1
C2
VO = 0.6V @ 1.5A
LM2831
www.ti.com
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
8.2.2 LM2831X Design Example 2
Figure 24. LM2831X (1.6 MHz): VIN =5V,VO= 0.6 V at 1.5 A
Table 2. Bill of Materials
PART ID PART VALUE MANUFACTURER PART NUMBER
U1 1.5-A Buck Regulator TI LM2831X
C1, Input Capacitor 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
C2, Output Capacitor 2x22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
D1, Catch Diode 0.3 VfSchottky 1.5 A, 30 VRTOSHIBA CRS08
L1 3.3 µH, 2.2 A TDK VLCF5020T- 3R3N2R0-1
R2 10.0 kΩ, 1% Vishay CRCW08051000F
R1 0 Ω
R3 100 kΩ, 1% Vishay CRCW08051003F
Copyright © 2006–2015, Texas Instruments Incorporated Submit Documentation Feedback 17
Product Folder Links: LM2831
GND
FB
EN
VIN SW
VIN = 5V
C1
R3
D1
L1
LM2831
R2
R1
C2
VO = 3.3V @ 1.5A
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
8.2.3 LM2831X Design Example 3
Figure 25. LM2831X (1.6 MHz): VIN =5V,VO= 3.3 V at 1.5 A
Table 3. Bill of Materials
PART ID PART VALUE MANUFACTURER PART NUMBER
U1 1.5-A Buck Regulator TI LM2831X
C1, Input Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
C2, Output Cap 2x22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
D1, Catch Diode 0.3 VfSchottky 1.5 A, 30 VRTOSHIBA CRS08
L1 2.7 µH 2.3 A TDK VLCF5020T-2R7N2R2-1
R2 10.0 kΩ, 1% Vishay CRCW08051002F
R1 45.3 kΩ, 1% Vishay CRCW08054532F
R3 100 kΩ, 1% Vishay CRCW08051003F
18 Submit Documentation Feedback Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM2831
GND
FB
EN
VIN SW
VIN = 5V
C1
R3
D1
L1
LM2831
R2
R1
C2
VO = 3.3V @ 1.5A
LM2831
www.ti.com
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
8.2.4 LM2831Y Design Example 4
Figure 26. LM2831Y (550 kHz): VIN =5V,VOUT = 3.3 V at 1.5 A
Table 4. Bill of Materials
PART ID PART VALUE MANUFACTURER PART NUMBER
U1 1.5-A Buck Regulator TI LM2831Y
C1, Input Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
C2, Output Cap 2x22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
D1, Catch Diode 0.3 VfSchottky 1.5 A, 30 VRTOSHIBA CRS08
L1 4.7 µH 2.1 A TDK SLF7045T-4R7M2R0-PF
R1 45.3 kΩ, 1% Vishay CRCW080545K3FKEA
R2 10.0 kΩ, 1% Vishay CRCW08051002F
Copyright © 2006–2015, Texas Instruments Incorporated Submit Documentation Feedback 19
Product Folder Links: LM2831
GND
FB
EN
VIN SW
VIN = 5V
C1
R3
D1
L1
LM2831
R2
R1
C2
VO = 1.2V @ 1.5A
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
8.2.5 LM2831Y Design Example 5
Figure 27. LM2831Y (550 kHz): VIN =5V,VOUT = 1.2 V at 1.5 A
Table 5. Bill of Materials
PART ID PART VALUE MANUFACTURER PART NUMBER
U1 1.5-A Buck Regulator TI LM2831Y
C1, Input Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
C2, Output Cap 2x22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
D1, Catch Diode 0.3 VfSchottky 1.5 A, 30 VRTOSHIBA CRS08
L1 6.8 µH 1.8 A TDK SLF7045T-6R8M1R7
R1 10.0 kΩ, 1% Vishay CRCW08051002F
R2 10.0 kΩ, 1% Vishay CRCW08051002F
20 Submit Documentation Feedback Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM2831
GND
FB
EN
VIN SW
VIN = 5V
C1
R3
D1
L1
LM2831
R2
R1
C2
VO = 3.3V @ 1.5A
LM2831
www.ti.com
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
8.2.6 LM2831Z Design Example 6
Figure 28. LM2831Z (3 MHz): VIN =5V,VO= 3.3 V at 1.5 A
Table 6. Bill of Materials
PART ID PART VALUE MANUFACTURER PART NUMBER
U1 1.5-A Buck Regulator TI LM2831Z
C1, Input Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
C2, Output Cap 2x22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
D1, Catch Diode 0.3 VfSchottky 1.5 A, 30 VRTOSHIBA CRS08
L1 1.6 µH 2.0 A TDK VLCF4018T-1R6N1R7-2
R2 10.0 kΩ, 1% Vishay CRCW08051002F
R1 45.3 kΩ, 1% Vishay CRCW08054532F
R3 100 kΩ, 1% Vishay CRCW08051003F
Copyright © 2006–2015, Texas Instruments Incorporated Submit Documentation Feedback 21
Product Folder Links: LM2831
GND
FB
EN
VIN SW
VIN = 5V
C1
R3
D1
L1
LM2831
R2
R1
C2
VO = 1.2V @ 1.5A
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
8.2.7 LM2831Z Design Example 7
Figure 29. LM2831Z (3 MHz): VIN =5V,VO= 1.2 V at 1.5 A
Table 7. Bill of Materials
PART ID PART VALUE MANUFACTURER PART NUMBER
U1 1.5-A Buck Regulator TI LM2831Z
C1, Input Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
C2, Output Cap 2x22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
D1, Catch Diode 0.3 VfSchottky 1.5 A, 30 VRTOSHIBA CRS08
L1 1.6 µH, 2.0 A TDK VLCF4018T- 1R6N1R7-2
R2 10.0 kΩ, 1% Vishay CRCW08051002F
R1 10.0 kΩ, 1% Vishay CRCW08051002F
R3 100 kΩ, 1% Vishay CRCW08051003F
22 Submit Documentation Feedback Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM2831
LP3470M5X-3.08
U2
VINAVIND
LM2831
U3
U1
LM2831
SW
D1
FB
EN
L1
GND
C1
C2
R1
R2
C3 VINAVIND
SW
FB
EN
GND
D2
L2
C4
R4
R5
R6 3
1
2
VIN
RESET
4
5
LP3470
C7
VIN
VO= 3.3V @ 1.5A
VO= 1.2V @ 1.5A
R3
LM2831
www.ti.com
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
8.2.8 LM2831X Dual Converters with Delayed Enabled Design Example 8
Figure 30. LM2831X (1.6 MHz): VIN =5V,VO= 1.2 V at 1.5 A and 3.3 V at1.5 A
Table 8. Bill of Materials
PART ID PART VALUE MANUFACTURER PART NUMBER
U1, U2 1.5-A Buck Regulator TI LM2831X
U3 Power on Reset TI LP3470M5X-3.08
C1, C3 Input Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
C2, C4 Output Cap 2x22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
C7 Trr delay capacitor TDK
D1, D2 Catch Diode 0.3 VfSchottky 1.5 A, 30 VRTOSHIBA CRS08
L1, L2 3.3 µH, 2.2 A TDK VLCF5020T-3R3N2R0-1
R2, R4, R5 10.0 kΩ, 1% Vishay CRCW08051002F
R1, R6 45.3 kΩ, 1% Vishay CRCW08054532F
R3 100 kΩ, 1% Vishay CRCW08051003F
Copyright © 2006–2015, Texas Instruments Incorporated Submit Documentation Feedback 23
Product Folder Links: LM2831
LDO
C5
U2
D2
L2
R1
R2
EN FB
SW
VINA
VIND
GND VO = 3.3V @ 1.5A
VO = 5.0V @ 150mA
C4
C6
C2
C3
D1
L1
U1
C1
LM2831
VIN = 5V
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
8.2.9 LM2831X Buck Converter and Voltage Double Circuit With LDO Follower Design Example 9
Figure 31. LM2831X (1.6 MHz): VIN =5V,VO= 3.3 V at 1.5 A and LP2986-5.0 at 150 mA
Table 9. Bill of Materials
PART ID PART VALUE MANUFACTURER PART NUMBER
U1 1.5-A Buck Regulator TI LM2831X
U2 200-mA LDO TI LP2986-5.0
C1, Input Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
C2, Output Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M
C3 – C6 2.2 µF, 6.3 V, X5R TDK C1608X5R0J225M
D1, Catch Diode 0.3 VfSchottky 1.5 A, 30 VRTOSHIBA CRS08
D2 0.4 VfSchottky 20 VR, 500 mA ON Semi MBR0520
L2 10 µH, 800 mA CoilCraft ME3220-103
L1 3.3 µH, 2.2 A TDK VLCF5020T-3R3N2R0-1
R2 45.3 kΩ, 1% Vishay CRCW08054532F
R1 10.0 kΩ, 1% Vishay CRCW08051002F
24 Submit Documentation Feedback Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM2831
D = VOUT + VD + VDCR
VIN + VD + VDCR - VSW
OUT D
IN D SW
V V
D
V V V
+
=
+ -
OUT
OUT LOSS
P
P P
h =
+
OUT
IN
P
P
h =
LM2831
www.ti.com
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
9 Power Supply Recommendations
The LM2831 device is designed to operate from various DC power supplies. The impedance of the input supply
rail should be low enough that the input current transient does not cause a drop below the UVLO level. If the
input supply is connected by using long wires, additional bulk capacitance may be required in addition to normal
input capacitor.
10 Layout
10.1 Layout Guidelines
When planning layout there are a few things to consider when trying to achieve a clean, regulated output. The
most important consideration is the close coupling of the GND connections of the input capacitor and the catch
diode D1. These ground ends should be close to one another and be connected to the GND plane with at least
two through-holes. Place these components as close to the IC as possible. Next in importance is the location of
the GND connection of the output capacitor, which should be near the GND connections of CIN and D1. There
should be a continuous ground plane on the bottom layer of a two-layer board except under the switching node
island. The FB pin is a high impedance node and care should be taken to make the FB trace short to avoid noise
pickup and inaccurate regulation. The feedback resistors should be placed as close as possible to the IC, with
the GND of R1 placed as close as possible to the GND of the IC. The VOUT trace to R2 should be routed away
from the inductor and any other traces that are switching. High AC currents flow through the VIN, SW and VOUT
traces, so they should be as short and wide as possible. However, making the traces wide increases radiated
noise, so the designer must make this trade-off. Radiated noise can be decreased by choosing a shielded
inductor. The remaining components should also be placed as close as possible to the IC. See Application Note
AN-1229 SNVA054 for further considerations and the LM2831 demo board as an example of a 4-layer layout.
10.1.1 Calculating Efficiency and Junction Temperature
The complete LM2831 DC-DC converter efficiency can be calculated in the following manner.
(15)
Or
(16)
Calculations for determining the most significant power losses are shown below. Other losses totaling less than
2% are not discussed.
Power loss (PLOSS) is the sum of two basic types of losses in the converter: switching and conduction.
Conduction losses usually dominate at higher output loads, whereas switching losses remain relatively fixed and
dominate at lower output loads. The first step in determining the losses is to calculate the duty cycle (D):
(17)
VSW is the voltage drop across the internal PFET when it is on, and is equal to:
VSW = IOUT × RDSON (18)
VDis the forward voltage drop across the Schottky catch diode. It can be obtained from the diode manufactures
Electrical Characteristics section. If the voltage drop across the inductor (VDCR) is accounted for, the equation
becomes:
(19)
The conduction losses in the free-wheeling Schottky diode are calculated as follows:
PDIODE = VD× IOUT × (1-D) (20)
Copyright © 2006–2015, Texas Instruments Incorporated Submit Documentation Feedback 25
Product Folder Links: LM2831
PCOND= (IOUT2 x D) 1
3
1 + x'iL
IOUT
2RDSON
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
Layout Guidelines (continued)
Often this is the single most significant power loss in the circuit. Care should be taken to choose a Schottky
diode that has a low forward voltage drop.
Another significant external power loss is the conduction loss in the output inductor. The equation can be
simplified to:
PIND = IOUT2× RDCR (21)
The LM2831 conduction loss is mainly associated with the internal PFET:
(22)
If the inductor ripple current is fairly small, the conduction losses can be simplified to:
PCOND = IOUT2× RDSON × D (23)
Switching losses are also associated with the internal PFET. They occur during the switch on and off transition
periods, where voltages and currents overlap resulting in power loss. The simplest means to determine this loss
is to empirically measuring the rise and fall times (10% to 90%) of the switch at the switch node.
Switching power loss is calculated as follows:
PSWR = 1/2(VIN × IOUT × FSW × TRISE) (24)
PSWF = 1/2(VIN × IOUT × FSW × TFALL) (25)
PSW = PSWR + PSWF (26)
Another loss is the power required for operation of the internal circuitry:
PQ= IQ× VIN (27)
IQis the quiescent operating current, and is typically around 2.5 mA for the 0.55-MHz frequency option.
Typical application power losses are:
Table 10. Power Loss Tabulation
PARAMETER VALUE PARAMETER VALUE
VIN 5 V
VOUT 3.3 V POUT 4.125 W
IOUT 1.25 A
VD0.45 V PDIODE 188 mW
FSW 550 kHz
IQ2.5 mA PQ12.5 mW
TRISE 4 nS PSWR 7 mW
TFALL 4 nS PSWF 7 mW
RDS(ON) 150 mΩPCOND 156 mW
INDDCR 70 mΩPIND 110 mW
D 0.667 PLOSS 481 mW
η88% PINTERNAL 183 mW
ΣPCOND + PSW + PDIODE + PIND + PQ= PLOSS (28)
ΣPCOND + PSWF + PSWR + PQ= PINTERNAL (29)
PINTERNAL = 183 mW (30)
26 Submit Documentation Feedback Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM2831
J C
JC
T T
R
Power
F
-
=
J A
JA
T T
R
Power
q
-
=
T
R
Power
q
D
=
LM2831
www.ti.com
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
10.1.2 Thermal Definitions
TJChip junction temperature
TAAmbient temperature
RθJC Thermal resistance from chip junction to device case
RθJA Thermal resistance from chip junction to ambient air
Heat in the LM2831 due to internal power dissipation is removed through conduction and/or convection.
Conduction Heat transfer occurs through cross sectional areas of material. Depending on the material, the
transfer of heat can be considered to have poor to good thermal conductivity properties (insulator
vs. conductor).
Heat Transfer goes as:
Silicon →package →lead frame →PCB
Convection: Heat transfer is by means of airflow. This could be from a fan or natural convection. Natural
convection occurs when air currents rise from the hot device to cooler air.
Thermal impedance is defined as:
(31)
Thermal impedance from the silicon junction to the ambient air is defined as:
(32)
The PCB size, weight of copper used to route traces and ground plane, and number of layers within the PCB can
greatly effect RθJA. The type and number of thermal vias can also make a large difference in the thermal
impedance. Thermal vias are necessary in most applications. They conduct heat from the surface of the PCB to
the ground plane. Four to six thermal vias should be placed under the exposed pad to the ground plane if the
WSON package is used.
Thermal impedance also depends on the thermal properties of the application operating conditions (Vin, Vo, Io,
and so forth), and the surrounding circuitry.
10.1.2.1 Silicon Junction Temperature Determination Method 1
To accurately measure the silicon temperature for a given application, two methods can be used. The first
method requires the user to know the thermal impedance of the silicon junction to top case temperature.
Some clarification must be made before we go any further.
RθJC is the thermal impedance from all six sides of an IC package to silicon junction.
RΦJC is the thermal impedance from top case to the silicon junction.
In this data sheet we will use RΦJC so that it allows the user to measure top case temperature with a small
thermocouple attached to the top case.
RΦJC is approximately 30°C/Watt for the 6-pin WSON package with the exposed pad. Knowing the internal
dissipation from the efficiency calculation given previously, and the case temperature, which can be empirically
measured on the bench we have:
(33)
Therefore:
Tj= (RΦJC × PLOSS)+TC(34)
From the previous example:
Tj= (RΦJC × PINTERNAL)+TC(35)
Tj= 30°C/W × 0.189 W + TC(36)
Copyright © 2006–2015, Texas Instruments Incorporated Submit Documentation Feedback 27
Product Folder Links: LM2831
Die Attach
Material
Mold Compound
Gold Wire
Exposed Die
Attach Pad
Die
Cu
Exposed
Contact
JA
165 C 144 C
R 111 C / W
189 mW
q
° - °
= = °
JA
INTERNAL
165 C Ta
R
P
q
° -
=
LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
The second method can give a very accurate silicon junction temperature.
The first step is to determine RθJA of the application. The LM2831 has overtemperature protection circuitry. When
the silicon temperature reaches 165°C, the device stops switching. The protection circuitry has a hysteresis of
about 15°C. Once the silicon temperature has decreased to approximately 150°C, the device will start to switch
again. Knowing this, the RθJA for any application can be characterized during the early stages of the design one
may calculate the RθJA by placing the PCB circuit into a thermal chamber. Raise the ambient temperature in the
given working application until the circuit enters thermal shutdown. If the SW-pin is monitored, it will be obvious
when the internal PFET stops switching, indicating a junction temperature of 165°C. Knowing the internal power
dissipation from the above methods, the junction temperature, and the ambient temperature RθJA can be
determined.
(37)
Once this is determined, the maximum ambient temperature allowed for a desired junction temperature can be
found.
An example of calculating RθJA for an application using the Texas Instruments LM2831 WSON demonstration
board is shown below.
The four layer PCB is constructed using FR4 with ½ oz copper traces. The copper ground plane is on the bottom
layer. The ground plane is accessed by two vias. The board measures 3 cm × 3 cm. It was placed in an oven
with no forced airflow. The ambient temperature was raised to 144°C, and at that temperature, the device went
into thermal shutdown.
From the previous example:
PINTERNAL = 189 mW (38)
(39)
If the junction temperature was to be kept below 125°C, then the ambient temperature could not go above 109°C
Tj- (RθJA × PLOSS)=TA(40)
125°C - (111°C/W × 189 mW) = 104°C (41)
10.1.3 WSON Package
Figure 32. Internal WSON Connection
For certain high power applications, the PCB land may be modified to a "dog bone" shape (see Figure 33). By
increasing the size of ground plane, and adding thermal vias, the RθJA for the application can be reduced.
28 Submit Documentation Feedback Copyright © 2006–2015, Texas Instruments Incorporated
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LM2831
SNVS422D –AUGUST 2006–REVISED SEPTEMBER 2015
www.ti.com
11 Device and Documentation Support
11.1 Device Support
11.1.1 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
11.2 Documentation Support
11.2.1 Related Documentation
For related documentation, see the following:
AN-1229 SIMPLE SWITCHER ® PCB Layout Guidelines,SNVA054
11.3 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.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.4 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.5 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.6 Glossary
SLYZ022 —TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 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.
30 Submit Documentation Feedback Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM2831
PACKAGE OPTION ADDENDUM
www.ti.com 6-Feb-2020
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
LM2831XMF/NOPB ACTIVE SOT-23 DBV 5 1000 Green (RoHS
& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 SKYB
LM2831XMFX/NOPB ACTIVE SOT-23 DBV 5 3000 Green (RoHS
& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 SKYB
LM2831XSD NRND WSON NGG 6 1000 TBD Call TI Call TI -40 to 125 L193B
LM2831XSD/NOPB ACTIVE WSON NGG 6 1000 Green (RoHS
& no Sb/Br) SN Level-3-260C-168 HR -40 to 125 L193B
LM2831XSDX/NOPB ACTIVE WSON NGG 6 4500 Green (RoHS
& no Sb/Br) SN Level-3-260C-168 HR -40 to 125 L193B
LM2831YMF/NOPB ACTIVE SOT-23 DBV 5 1000 Green (RoHS
& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 SKZB
LM2831YMFX/NOPB ACTIVE SOT-23 DBV 5 3000 Green (RoHS
& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 SKZB
LM2831YSD/NOPB ACTIVE WSON NGG 6 1000 Green (RoHS
& no Sb/Br) SN Level-3-260C-168 HR -40 to 125 L194B
LM2831ZMF/NOPB ACTIVE SOT-23 DBV 5 1000 Green (RoHS
& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 SLAB
LM2831ZSD/NOPB ACTIVE WSON NGG 6 1000 Green (RoHS
& no Sb/Br) SN Level-3-260C-168 HR -40 to 125 L195B
(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 6-Feb-2020
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
LM2831XMF/NOPB SOT-23 DBV 5 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2831XMFX/NOPB SOT-23 DBV 5 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2831XSD WSON NGG 6 1000 178.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1
LM2831XSD/NOPB WSON NGG 6 1000 178.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1
LM2831XSDX/NOPB WSON NGG 6 4500 330.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1
LM2831YMF/NOPB SOT-23 DBV 5 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2831YMFX/NOPB SOT-23 DBV 5 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2831YSD/NOPB WSON NGG 6 1000 178.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1
LM2831ZMF/NOPB SOT-23 DBV 5 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2831ZSD/NOPB WSON NGG 6 1000 178.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 29-Sep-2019
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LM2831XMF/NOPB SOT-23 DBV 5 1000 210.0 185.0 35.0
LM2831XMFX/NOPB SOT-23 DBV 5 3000 210.0 185.0 35.0
LM2831XSD WSON NGG 6 1000 210.0 185.0 35.0
LM2831XSD/NOPB WSON NGG 6 1000 210.0 185.0 35.0
LM2831XSDX/NOPB WSON NGG 6 4500 367.0 367.0 35.0
LM2831YMF/NOPB SOT-23 DBV 5 1000 210.0 185.0 35.0
LM2831YMFX/NOPB SOT-23 DBV 5 3000 210.0 185.0 35.0
LM2831YSD/NOPB WSON NGG 6 1000 210.0 185.0 35.0
LM2831ZMF/NOPB SOT-23 DBV 5 1000 210.0 185.0 35.0
LM2831ZSD/NOPB WSON NGG 6 1000 210.0 185.0 35.0
PACKAGE MATERIALS INFORMATION
www.ti.com 29-Sep-2019
Pack Materials-Page 2
www.ti.com
PACKAGE OUTLINE
C
0.22
0.08 TYP
0.25
3.0
2.6
2X 0.95
1.9
1.45
0.90
0.15
0.00 TYP
5X 0.5
0.3
0.6
0.3 TYP
8
0 TYP
1.9
A
3.05
2.75
B
1.75
1.45
(1.1)
SOT-23 - 1.45 mm max heightDBV0005A
SMALL OUTLINE TRANSISTOR
4214839/E 09/2019
NOTES:
1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing
per ASME Y14.5M.
2. This drawing is subject to change without notice.
3. Refernce JEDEC MO-178.
4. Body dimensions do not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, or gate burrs shall not
exceed 0.15 mm per side.
0.2 C A B
1
34
5
2
INDEX AREA
PIN 1
GAGE PLANE
SEATING PLANE
0.1 C
SCALE 4.000
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EXAMPLE BOARD LAYOUT
0.07 MAX
ARROUND 0.07 MIN
ARROUND
5X (1.1)
5X (0.6)
(2.6)
(1.9)
2X (0.95)
(R0.05) TYP
4214839/E 09/2019
SOT-23 - 1.45 mm max heightDBV0005A
SMALL OUTLINE TRANSISTOR
NOTES: (continued)
5. Publication IPC-7351 may have alternate designs.
6. Solder mask tolerances between and around signal pads can vary based on board fabrication site.
SYMM
LAND PATTERN EXAMPLE
EXPOSED METAL SHOWN
SCALE:15X
PKG
1
34
5
2
SOLDER MASK
OPENING
METAL UNDER
SOLDER MASK
SOLDER MASK
DEFINED
EXPOSED METAL
METAL
SOLDER MASK
OPENING
NON SOLDER MASK
DEFINED
(PREFERRED)
SOLDER MASK DETAILS
EXPOSED METAL
www.ti.com
EXAMPLE STENCIL DESIGN
(2.6)
(1.9)
2X(0.95)
5X (1.1)
5X (0.6)
(R0.05) TYP
SOT-23 - 1.45 mm max heightDBV0005A
SMALL OUTLINE TRANSISTOR
4214839/E 09/2019
NOTES: (continued)
7. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
8. Board assembly site may have different recommendations for stencil design.
SOLDER PASTE EXAMPLE
BASED ON 0.125 mm THICK STENCIL
SCALE:15X
SYMM
PKG
1
34
5
2
MECHANICAL DATA
NGG0006A
www.ti.com
SDE06A (Rev A)
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