SG6846LDZ - System General Corporation

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

FEATURES

 Two-level OCP with 96mS delay time

 Peak-current-mode operation with cycle-by-cycle

current limiting

 PWM frequency continuously decreasing w/ burst

mode at light loads

 Low start-up current (8uA)

 Low operating current (3.7mA)

 VDD over-voltage protection (OVP)

 AC input brownout protection with hysteresis

 Programmable over-temperature protection (OTP)

 Constant power limit over universal AC input range

 Internal latch circuit for OTP, OVP, OCP

 Very few external components

APPLICATIONS

General-purpose switch mode power supplies and

flyback power converters, including:

 Power adapters

 Open-frame SMPS

 Specifically fit for SMPS with surge-current output,

such as for printers, scanners, motor drivers, etc.

DESCRIPTION

The highly integrated SG6846 series of PWM

controllers provides several features to enhance the

performance of flyback converters. To minimize standby

power consumption, a proprietary green-mode function

provides off-time modulation to continuously decrease

the switching frequency under light-load conditions.

Under zero-load conditions, the power supply enters

burst-mode. This completely shuts off PWM output. The

output restarts just before the supply voltage drops below

the UVLO lower limit. This green-mode function enables

power supplies to easily meet international power

conservation requirements.

The SG6846 is especially designed for SMPS with

surge-current output. It is incorporated with a two-level

OCP function. Besides the cycle-by-cycle current limiting,

if the switching current is higher than 2/3 of the

peak-current threshold for a delay time, over-current

protection will be activated such that the SG6846 will be

totally shutdown. Other protection functions include: AC

input brownout protection with hysteresis, and VDD

over-voltage protection. For over-temperature protection,

an external NTC thermistor can be applied to sense the

ambient temperature. When OCP, VDD OVP, or OTP are

activated, an internal latch circuit is used to latch-off the

controller. The latch will reset when the VDD supply is

removed.

Other features of this controller include: Built-in

synchronized slope compensation, proprietary internal

compensation for constant output power limit over

universal AC input range. Also, the gate output is clamped

at 18V to protect the external MOSFET from over-voltage

damage.

The SG6846 series controllers are available in both

8-pin DIP and SO packages.

TYPICAL APPLICATION

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

MARKING DIAGRAMS PIN CONFIGURATION

ORDERING INFORMATION

Part Number Package OTP Mode

SG6846LS 8-Pin SOP Latch off

SG6846LD 8-Pin DIP Latch off

SG6846CS 8-Pin SOP Hysteresis

SG6846CD 8-Pin DIP Hysteresis

SG6846LSZ 8-Pin SOP (Lead Free) Latch off

SG6846LDZ 8-Pin DIP (Lead Free) Latch off

SG6846CSZ 8-Pin SOP (Lead Free) Hysteresis

SG6846CDZ 8-Pin DIP (Lead Free) Hysteresis

SG6846FTP

MXXXXXXYYWWV

8

1

F: L = OTP Latch

C = Hysteresis OTP

T: D = DIP, S = SOP

P: Null = regular

Z = Lead free

M: Mask version

XXXXXX: Wafer Lot

YY: Year; WW: Week

V: Assembl

y

Location

RI

VIN

GATE

VDD

SENSE

RT

GND

FB

3

1

2

5

6

8

7

4

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

PIN DESCRIPTIONS

Pin No. Symbol Function Description

1 GND Ground Ground.

2 FB Feedback

The signal from the external compensation circuit is fed into this pin. This FB pin and the

current-sense signal from Pin 6 determine the PWM duty cycle.

3 VIN

Line-voltage

Detection

Line-voltage detection. The line-voltage detection is used for brownout protection with

hysteresis. Constant output power limit over universal AC input range is also achieved using

this VIN signal. It is suggested to add low pass filter to filter out line ripple on bulk capacitor.

4 RI

Reference

Setting

A resistor from the RI pin to ground will generate a reference current source inside SG6846.

This determines the switching frequency. Increasing the resistance will reduce the switching

frequency. Using a 26kΩ resistor Ri results in a 65kHz switching frequency.

5 RT

Temperature

Detection

For over-temperature protection. An external NTC thermistor is connected from this pin to

GND pin. The impedance of the NTC will decrease at high temperatures. Once the voltage

of the RT pin drops below a threshold, PWM output will be disabled.

6 SENSE Current Sense

Current sense. The sensed voltage is used for peak-current-mode control and

cycle-by-cycle current limiting. If the switching current is higher than 2/3 of the peak-current

threshold for longer than 96ms, over-current protection will be activated. This two-level OCP

feature is especially suitable for SMPS with surge current output.

7 VDD Power Supply

Power Supply. The internal protection circuit will disable PWM output when VDD over

voltage.

8 GATE Driver Output

The totem-pole output driver for the power MOSFET. A soft driving waveform is

implemented for improved EMI.

BLOCK DIAGRAM (OTP LATCH VERSION)

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Test Condition Value Unit

VDD Supply Voltage 25 V

VL Input Voltage to VIN, FB, SENSE, RT, RI Pin -0.3 to 7V V

PD Power Dissipation at TA < 50°C DIP

SOP

800

400 mW

RΘ J-C Thermal Resistance Junction-Case DIP

SOP

67.1

41.2 °C/W

TJ Operating Ambient Temperature -40 to 125 °C

TSTG Storage Temperature Range -65 to +150 °C

TL Lead Temperature (Soldering) 10 sec DIP

10 sec SOP

260

230 °C

*All voltage values, except differential voltages, are given with respect to GND pin.

*Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device.

RECOMMENDED OPERATING JUNCTION TEMPERATURE: -30°C ~ 85°C*

*For proper operation

ELECTRICAL CHARACTERISTICS (VDD = 15V, TA = 27°C, unless noted)

VDD Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

VOP Continuously Operating Voltage 20 V

VTH-ON On Threshold Voltage 15.5 16.5 17.5 V

VTH-OFF Off Threshold Voltage 9.5 10.5 11.5 V

IDD-ST Start-Up Current VDD = 15V 8 30 uA

IDD-OP Operating Supply Current GATE Open 3.7 5 mA

VDD-OVP VDD Over Voltage Protection (Latch off) 22.6 23.6 24.6 V

TVDD-OVP VDD OVP Debounce Time RI = 26KΩ 100 usec

IDD-OVP VDD OVP Latch-up Holding Current VDD = 5V, TA = 27oC 45 uA

VDD-TH-G VDD Low-threshold Voltage to Exit Green-OFF

Mode

VTH(OFF) +

1.25 V

VIN Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

VIN-OFF PWM Turn-off Threshold Voltage 0.67 0.72 0.77 V

VIN-ON PWM Turn-on Threshold Voltage VIN-OFF +

0.2 V

Feedback Input Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

AV Input-Voltage to Current-Sense Attenuation 1/4.2 V/V

ZFB Input Impedance 4 5.5 7 KΩ

VFB0 FB Pin open voltage 6.2 V

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

Current Sense Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

ZCS Input Impedance 12 kΩ

TPD Delay to Output 100 200 nsec

BNK Leading Edge Blanking Time 360 nsec

VTH-P @VIN=1V Threshold Voltage for Current Limit VIN = 1V, RI = 26kΩ 0.83 V

VTH-P @VIN=3V Threshold Voltage for Current Limit VIN =3V, RI = 26kΩ 0.70 V

VTH-O @VIN=1V 2/3 Threshold Voltage for Current Limit VIN = 1V, RI = 26kΩ 0.61 V

VTH-O @VIN=3V 2/3 Threshold Voltage for Current Limit VIN =3V, RI = 26kΩ 0.51 V

TDELAY-OCP The Delay Time for Over-current Protection RI = 26KΩ 96 msec

Oscillator Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

FOSC PWM Frequency RI = 26kΩ 60 65 70 KHz

FOSC-GREEN Green-mode Frequency RI = 26kΩ 20 22.5 25 KHz

VN FB Pin Threshold for the Beginning of Green

Mode 2.1 V

VG Green-OFF Mode Voltage at FB pin 1.6 V

SG Slope for Green-Mode Modulation RI = 26kΩ 85 Hz/mV

FDV Frequency Variation Versus VDD Deviation VDD = 11.5V to 20V 5 %

FDT Frequency Variation Versus Temp. Deviation TA = -30 to 85 ℃ 1.5 5 %

Frequenc

y

VF

B

FOSC-GOFF: 0kHz

VN: 2.1V

PWM Frequency

VG: 1.6V

SG: 85Hz/mV

FOSC-GREEN: 22.5kHz

FOSC: 65kHz

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

PWM Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

DMAX Maximum Duty Cycle 80 85 90 %

VOL Output Voltage Low VDD = 15V, Io = 50mA 1.5 V

VOH Output Voltage High VDD = 12V, Io = 50mA 8V V

TR Rising Time VDD = 15V, CL=1nF 350 nsec

TF Falling Time VDD = 15V, CL=1nF 50 nsec

VCLAMP Gate Output Clamping Voltage VDD = 20V 18 V

Over Temperature Protection Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

IRT Output Current of RT Pin RI = 26kΩ 64 70 76 uA

VOTP-LATCH-OFF Threshold Voltage for Over-Temperature

Protection.

1.015 1.065 1.115 V

TDOTP-LATCH Over-Temperature Latch-Off Debounce. RI = 26kΩ 100 usec

VOTP-RESET OTP Release Voltage (for non-latch-off version) VOTP-LATCH-

OFF + 0.1

V

RI Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

RINOR R

I Operating Range 15.5 36 kΩ

RIMAX Max. RI value for Protection 216 kΩ

RIMIN Min. RI value for Protection 6 kΩ

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

TYPICAL CHARACTERISTICS

Start-up Threshold Voltage vs Temperature

15.5

16.0

16.5

17.0

17.5

-40 -25 -10 5 20 35 50 65 80 95 110 125

Temperature (℃)

VTH-ON (V)

Start-up Current vs Temperature

13.500

14.000

14.500

15.000

15.500

16.000

-40 -25 -10 5 20 35 50 65 80 95 110 125

Temperature (℃)

IDD-ST (uA)

PWM Turn-off Threshold Voltage vs

Temperature

0.400

0.500

0.600

0.700

0.800

0.900

1.000

-40 -25 - 10 5 20 35 50 65 80 95 110 125

Temperature (℃)

VIN-OFF (V)

Min. Opperating Voltage vs Temperature

9.5

9.7

9.9

10.1

10.3

10.5

10.7

10.9

11.1

11.3

11.5

- 40 - 25 -10 5 20 35 50 65 80 95 110 125

Temperature (℃)

VTH-OFF (V)

Start-up Current vs VDD Voltage

0

4

8

12

16

20

5101520

VDD (V)

IDD-ST (uA)

PWM Turn-on Threshold Voltage vs

Temperature

0.400

0.500

0.600

0.700

0.800

0.900

1.000

-40 -25 - 10 5 20 35 50 65 80 95 110 125

Temperature (℃)

VIN-ON (V)

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

PWM Frequency vs Temperature

64.600

64.700

64.800

64.900

65.000

65.100

65.200

65.300

-40 -25 -10 5 20 35 50 65 80 95 110 125

Temperature (℃)

FOSC (Khz)

Current-limit Threshold vs VIN Voltage

0

0.2

0.4

0.6

0.8

1

11.522.53

VIN (V)

VTH-P (V)

Output Current of pin RT vs Temperature

70.000

71.000

72.000

73.000

74.000

75.000

76.000

77.000

78.000

-40 -25 -10 5 20 35 50 65 80 95 110 125

Temperature (℃)

IRT (uA)

PWM Frequency vs FB Voltage (RI = 26KΩ)

0

20

40

60

1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3

VFB (V)

PWM Frequency (Khz)

2/3 Current-limit Threshold vs VIN Voltage

0

0.2

0.4

0.6

0.8

1

11.522.53

VIN (V)

VTH-O (V)

OTP Threshold Voltage vs Temperature

1.015

1.035

1.055

1.075

1.095

1.115

-40 -25 -10 5 20 35 50 65 80 95 110 125

Temperature (℃)

VOTP-OFF (V)

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

OPERATION DESCRIPTION

Start-up Operation

The turn-on/turn-off thresholds are fixed internally

at 16.5V/10.5V. To enable the SG6846 during start-up,

the hold-up capacitor must first be charged to 16.5V

through the start-up resistor.

The hold-up capacitor will continue to supply VDD

before energy can be delivered from the auxiliary winding

of the main transformer. The VDD must not drop below

10.5V during this start-up process. This UVLO hysteresis

window ensures that the hold-up capacitor can adequately

supply VDD during start-up.

The typical start-up current is only 8uA. This allows

a high resistance, low-wattage start-up resistor to be used,

to minimize power loss. A 1.5 MΩ/0.25W, start-up

resistor and a 10uF/25V VDD hold-up capacitor would be

sufficient for a universal input range.

The required operating current has been reduced to

3.7mA. This enables higher efficiency and reduces the

VDD hold-up capacitance requirement.

Green-Mode Operation

The proprietary green-mode function provides

off-time modulation to continuously decrease the

switching frequency under light-load conditions.

Maximum on time is limited to provide protection against

abnormal conditions. To further reduce power

consumption under zero-load condition, the PWM

oscillator will be completely turned off, and the power

supply will enter burst-mode. After the PWM oscillator is

turned off, the IC’s supply voltage VDD will drop

gradually. Before the VDD voltage drops below the

UVLO threshold, the PWM oscillator will be turned on

again. This green-mode function dramatically reduces

power consumption under light-load and zero-load

conditions. Power supplies using the SG6846 can easily

meet even the most restrictive international regulations

regarding standby power consumption.

Oscillator Operation

A resistor connected from the RI pin to GND

generates a reference current source inside the SG6846.

This current is used to determine the PWM frequency.

Increasing the resistance will decrease the amplitude of

the current source and reduce the PWM frequency. Using

a 26kΩ resistor Ri results in a corresponding 65kHz

switching frequency. The relationship between RI and the

switching frequency is:

)(k

Ω

=

i

PWM

R

f1690

(kHz) ---------------------------- (1)

If an open circuit or short circuit to ground occurs at the

RI pin, the internal protection circuit will immediately

shut down the controller.

Two-level Over-current Protection

The cycle-by-cycle current limiting will shut down

the PWM immediately when the switching current is over

the peak-current threshold. Additionally, when the

switching current is higher than 2/3 of the peak-current

threshold, the internal counter starts counting up. When

the switching current is lower than 2/3 of the peak current

threshold, the internal counter will count down. When the

total accumulated counting time is more than about 96ms

(Ri = 26kohm), the controller will be latched off.

This two-level OCP protection and up/down counter

are especially designed for SMPS with surge current

output such as those for printers, scanners, motor drivers,

etc.

Constant Output Power Limit

For constant output power limit over universal

input-voltage range, the peak-current threshold is

adjusted by the voltage of the VIN pin. Since the VIN pin

is connected to the rectified AC input line voltage through

the resistive divider, a higher line voltage will generate a

higher VIN voltage. The threshold voltage decreases as

the VIN voltage increases, making the max. output power

at high line input voltage equal to that at low line input.

Brownout Protection

Since the VIN pin is connected through a resistive

divider to the rectified AC input line voltage, it can also

be used for brownout protection. If the VIN voltage is less

than 0.72V, the PWM output will be shut off. As the VIN

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

voltage over 0.92V, the PWM output will be turned on

again. The hysteresis window for ON/OFF is around

0.2V.

VDD Over-voltage Protection

VDD over-voltage protection is built in to prevent

the controller from over-voltage destruction. When VDD

voltage is over 23.6V, the SG6846 is latched off.

Over-temperature Protection

An external NTC thermistor can be connected from

the RT pin to GND. The impedance of the NTC will

decrease at high temperatures. When the voltage of the

RT pin drops below 1.065V, the SG6846 will be turned

off. There are two options for the protection modes,

please see ORDER INFORMATION.

Noise immunity

Noise from the current sense or the control signal

may cause significant pulse width jitter, particularly in

continuous-conduction mode. Slope compensation helps

alleviate this problem. Good placement and layout

practices should be followed. The designer should

avoiding long PCB traces and component leads.

Compensation and filter components should be located

near the SG6846.

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

REFERENCE CIRCUIT

Application circuit for 32V/16V output

F1

21

+

C2

R16

21

+C12

21

+C13

FB

P16V P32V

P16V

CX1

32V

RI

4

VI N

3

FB

2

GND

1

RT 5

SENSE 6

VDD 7

GAT E 8

U1

12

34

LF2

21

+

C3

21

+

C5

1 2

3 4

LF1

VZ1

t

RT1

R1 R2

R3

R4

R12 C4

21

D2

C6

21

D1

12

43

U2

R18

R15

R20

A K

R

U3 R21

R19

C9

1

3

2

D4

R7

R13

R14

1

23

Q1

L1

C7

2

1

3

4

BD1

5

1

7 9

11

13

3

6

10

TX1

R17

21

+C14

21

+C15

16V

C11

1

3

2

D5

L2

P32V

P16V

21

D3

1 2

L4

R8

R9

R5

21

+

C1

R6

R10

NTC1

CX2

P1

P2

FB

1 2

L3

21

+

C16

21

+

C17

CY1

CY2

P7

R11

FB

16V

32V

P32V

P16V

P32VP16V

P16V

BOM

PART NO. VALUE PART NO. VALUE PART NO. VALUE

R1, R2, R3, R4 470KΩ +/-5% C4 103 P 630V D3 FR103 1.0A 200V

R8, R9 S1MΩ +/-1% C10,C11 102 P 1KV BD1 DBL406G

R5 16K2Ω +/-1% C6,C7 102 P 50V D4 BYT28-300

R15 1K5Ω +/-5% C9 222 P 50V D5 BYV32-150

R13 10Ω +/-5% C14,C17 470u 25V F1 250V4A QUICK

R18 4K7Ω +/-5% C15 220u 25V L1,L2 1.8uH

R21 15KΩ +/-1% C13,C16 220u 50V L4 10uH

R7 27KΩ +/-5% C2 150u 400V U3 TL431 +/-1%

R6 330Ω +/-1% C1 4u7 50V U1 SG 6846

R19 102KΩ +/-1% C3 10u 50V U2 PC817

R14 0Ω22 +/-5% CX1 X1 0.47u 275V Q1 7NB60

R16, R17 1W 20Ω +/-5% C8 Y2 222P 250V TX1 EI-33

R11 20KΩ +/-5% C5 100u 50V RT1 SCK053

R12 100KΩ +/-5% CX2 X2 0.1uF 275V VZ1 14ψ 470V

R20 887KΩ +/-1% D1 1N4148

R22 10KΩ +/-1% D2 BYV95C

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

PACKAGE INFORMATION

DIP-8 Outline Dimensions

41

85

D

E1

EeB

A1

A2

A

b

b1

L

e

°

Θ

Dimension

Millimeter Inch

Symbol Min. Typ. Max. Min. Typ. Max.

A 5.334 0.210

A1 0.381 0.015

A2 3.175 3.302 3.429 0.125 0.130 0.135

b 1.524 0.060

b1 0.457 0.018

D 9.017 9.271 10.160 0.355 0.365 0.400

E 7.620 0.300

E1 6.223 6.350 6.477 0.245 0.250 0.255

e 2.540 0.100

L 2.921 3.302 3.810 0.115 0.130 0.150

eB 8.509 9.017 9.525 0.335 0.355 0.375

θ˚ 0˚ 7˚ 15˚ 0˚ 7˚ 15˚

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

SOP-8 Outline Dimensions

Θ

14

85

H

E

e

b

A

A1

D

C

F

L

Dimension:

Millimeter Inch

Symbol Min. Typ. Max. Min. Typ. Max.

A 1.346 1.752 0.053 0.069

A1 0.101 0.254 0.004 0.010

b 0.406 0.016

c 0.203 0.008

D 4.648 4.978 0.183 0.196

E 3.810 3.987 0.150 0.157

e 1.270 0.050

F

0.381X45˚

0.015X45˚

H 5.791 6.197 0.228 0.244

L 0.406 1.270 0.016 0.050

θ˚ 0˚ 8˚ 0˚ 8˚

Product Specification

Highly-Integrated Green-Mode PWM Controller SG6846

Version 1.0(IAO33.0008.B0) Sep. 30, 2004

DISCLAIMERS

LIFE SUPPORT

System General’s products are not designed to be used as components in devices intended to support or sustain human

life. Use of System General’s products in components intended for surgical implant into the body, or other applications in

which failure of System General’s products could create a situation where personal death or injury may occur, is not

authorized without the express written approval of System General’s Chief Executive Officer. System General will not be

held liable for any damages or claims resulting from the use of its products in medical applications.

MILITARY

System General's products are not designed for use in military applications. Use of System General’s products in

military applications is not authorized without the express written approval of System General’s Chief Executive Officer.

System General will not be held liable for any damages or claims resulting from the use of its products in military

applications.

RIGHT TO MAKE CHANGES

System General reserves the right to change this document and/or this product without notice. Customers are advised

to consult their System General sales representative before ordering.