Datasheet SG6841_SYSTEMGENERAL, datasheet Datasheet

Product Specification

High-integrated Green-mode PWM Controller SG6841

FEATURES

 Green-mode PWM to support “Blue Angel” Norm  Low start up current 30uA  Low operation current 3mA  Leading-edge blanking  Built-in synchronized slope compensation

 Constant output power limit for universal AC input

 Current mode operation  Cycle-by-cycle current limiting  Under voltage lockout (UVLO)  Programmable PWM frequency  GATE output maximum voltage clamped at 18V  Totem pole output includes soft driving for better

EMI

 Build-in limited-power-control to meet safety

requirement

 Programmable over-temperature protection  Few external components & low cost solution

APPLICATIONS

General-purpose switching mode power supplies

and flyback power converters, and

 Power Adapter  Open-frame SMPS  Battery Charger Adapter

DESCRIPTION

This highly integrated PWM controllers, SG6841 series, provides several features to enhance the performance of low power flyback converters. To minimize standby power consumption, the proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. This green-mode function assists the power supply to easily meet the power conservation requirement. Due to BiCMOS process, the start-up current and operation current is reduced to 30uA and 3mA, respectively, to improve power conversion efficiency. Large start-up resistance can be used for further power saving. Built-in synchronized slope compensation ensures the stability of peak current mode control. A proprietary internal compensation ensures constant output power limit for universal AC input voltage from 90VAC to 264VAC.

SG6841 provides many protection functions. Pulse by pulse current limit ensures a constant output current under short circuit. If a short circuit failure or over load happens, the SG6841 will shut off after a continuous high voltage detection on FB pin. The gate output is clamped at 18V to protect the power MOS from over voltage damage. An external NTC thermistor can be applied to sense the ambient temperature for over-temperature protection. The SG6841 series are available in 8-pin DIP and SO packages.

TYPICAL APPLICAT ION

From bridge re ctifie r

127~ 373VDC

RT

RA

RIN

VIN

RT

SG6842

RI

FB

GND

VDD

GATE

SENSE

C

IN

©System General Corp. - 1 - www.sg.com.tw

Version 1.7 (IRO33.0001.B1) JUL.25,2003

D1

Rg

From auxiliary

winding

Q1

R

S

Product Specification

High-integrated Green-mode PWM Controller SG6841

MARKING DIAGRAMS

8

T: D = DIP, S = SOP

XXXXXXX: Wafer Lot

SG6841T

XXXXXXXYYWWV

YY: Year; WW: Week

V: Assembly Location

1

ORDERING INFORMATION

Part Number Package

SG6841S 8-Pin SOP

SG6841D 8-Pin DI P

PIN DESCRIPT IONS

PIN CONFIGURATION

GND

FB

VIN

Ri

1

2

3

4

Gate

8

VDD

7

Sense

6

5

RT

Pin No. Symbol Function Description

1 GND Ground Ground.

2 FB Feedback

3 VIN Start-Up Input

4 Ri Referenc e Setting

5 RT

6 SENSE Current S ense

7 VDD Power supply

8 GATE Driver Output

Temperature

Protec tion

The signal from external compensation circuit is feed into this pin. The PW M duty cycle is

determined by this FB pin and current sens e signal from Pin 6.

This pin is pulled high to the rectified line input through a resistor for start-up. Since the

start-up current requir ement f or SG6841 is very small, a large start-up resistance can be

used to minimize power loss. Under normal operation, this pin is also used to detect lin e

voltage to compensate for c onstant output power limit f or universal AC input.

A resistor from R I pin to ground will generate a const ant current source forSG6841. This

current is used to charge an internal capacitor and hence the switching fr equency are

determined. Increasing the resistance will decrease the current sourc e and reduce the

switching frequency. A 26kΩ resistor R

65kHz switching frequency.

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

to ground. The impedance of the NTC will decrease under high temperature. Once the

voltage on RT pin drops below a fixed limit, the PWM output will be disabled.

Current s ense. The s ensed voltage is used for current mode c ontrol and puls e-by-pulse

current limiting. If a short circuit failure happens on current sense resistor, the SG6841

will shut off after a continuous low voltage detection on SENSE pin.

Power Supply.

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

implemented to improve EMI.

creates a 50uA constant current Ii and generates

i

©System General Corp. - 2 - www.sg.com.tw

Version 1.7 (IRO33.0001.B1) JUL.25,2003

Product Specification

High-integrated Green-mode PWM Controller SG6841

BLOCK DIAGRAM

1

GND

RI

4

QS

Limited Power Controller

VDD

ON/OFF

Driver

OSC

R

4.2V

Green Mode Controll er

Comp

Slope Compensation

2R

R

8

GATE

6

SENSE

6V

2

FB

VIN

VDD

RT

0.85V

IRT

+

_

+

_

16V/10V

+

_

0.65V

UVLO

Internal BIAS

3

7

5

©System General Corp. - 3 - www.sg.com.tw

Version 1.7 (IRO33.0001.B1) JUL.25,2003

Product Specification

High-integrated Green-mode PWM Controller SG6841

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

VDD

I

Gate Out put Current 500 mA

OUT

VFB Input Voltage to FB Pin -0.3 to 7V V

V

Input Voltage to SENSE Pin -0.3 to 7V V

Sense

V

RT

VRI Input Voltage to Ri Pin -0.3 to 7V V

PD Power Dissipation 1 W

RΘ j-a

TJ Operating Junction T emperature 150 ℃

TA Operating Ambient T emperature -30 to 85 ℃

Tstg Storage Temperature Range -55 to +150 ℃

ESD Capability, HBM model 3.0 kV

ESD Capability, Machine model 250 V

DC Supply Voltage

Zener clamp

Zener current

Input Voltage to RT Pin -0.3 to 7V V

Thermal Resistance Junction-air

DIP

SOP

30

32

10

82.5

141

V

mA

℃/W

RECOMMENDED OPERATING CONDITIONS

Symbol Parameter Value Unit

VDD DC Supply Voltage <20 V

TA Operating Ambient Temperature -20 to +85

RI Current s ource Setting 26 kohms

℃

ELE CTRICAL CHARACTERISTICS Feedback Input Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

AV Input-voltage to current-sense attenuation 1/3.25 1/3 1/2.75 V/V

ZFB Input impedance 2 4.5 8 kΩ

IFB Bias current 2 mA

VOZ Input voltage for zer o duty cycle 1.2 V

©System General Corp. - 4 - www.sg.com.tw

Version 1.7 (IRO33.0001.B1) JUL.25,2003

Product Specification

High-integrated Green-mode PWM Controller SG6841

Current Sense Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

ZCS Input impedance 8 12 16 KΩ

TPD Delay to Output 150 200 ns ec

VTH Threshold voltage for current limit I

= 0 uA 0.8 0.85 0.9 V

VIN

∆VTH @ I

V

Threshold voltage for I

SENSE0

Tdelay-lps The delay time of limited-power-control RI=26KOhms 31 msec

The change of threshold voltage versus the input

VIN

current of th e Vin

= 80uA I

VIN

I

= 220 uA -0.09 -0.15 -0.21 V

VIN

= 80 uA 0.73 0.81 0.89 V

VIN

Oscillator Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

F

Frequency in nominal mode RI=26KOhms 60 65 70 KHz

OSC

Fosc-green Frequenc y in green mode RI=26KOhms 10 16 KHz

VG End of green mode volt age at FB pin 1.9 V

VN Beginning of frequency reducing at FB pin 2.6 V

SG Slope for green mode modulation RI=26KOhms 50 80 120 Hz/mV

FDV Frequenc y variation versus VDD deviation VDD=10 to 20V 5 %

FDT Frequency variation versus Temp. deviation TA=-30 to 85 ℃ 5 %

PWM Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

DC

Maximum Duty Cycle 75 80 90 %

(MAX)

DC

Minimum Duty Cycle - - 0 %

(MIN)

Bnk Leading edge blanking time 200 270 350 nsec

Output Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

VOL Output Voltage Low VDD = 12V, Io = 150mA 1.5 V

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

tr Rising Time VDD =13V, CL=1nF 150 250 350 nsec

tf Falling Time VDD =13V, CL=1nF 30 50 90 nsec

Under-voltage Lockout Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

V

Start Threshold Voltage 15 16 17 V

TH(ON)

V

Min. Operating Voltage 9 10 11 V

DD(min)

©System General Corp. - 5 - www.sg.com.tw

Version 1.7 (IRO33.0001.B1) JUL.25,2003

Product Specification

High-integrated Green-mode PWM Controller SG6841

Over-Temperature Protection Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

IRT Output current of pin RT RI=26KOhms 92 100 108 uA

V

OTP,STOP

V

OTP,START

Threshold voltage for over-temperature protection.

Turn-off point. Duty cycle is reduced to 0%.

Threshold voltage for over-temperature protection.

Starting point. Duty cycle starts to decrease.

0.585 0.62 0.655 V

0.65 V

Total Standby Current Section

Symbol Parameter Test Condition Min. Typ. Max. Unit

I

DD ST

I

DD OP

Start-up Current VDD=14.5V 30 40 uA Operating Supply Curr ent FB=SENSE=0V

GATE=1000pF VDD=15.5V

- 3 5 mA

©System General Corp. - 6 - www.sg.com.tw

Version 1.7 (IRO33.0001.B1) JUL.25,2003

Product Specification

High-integrated Green-mode PWM Controller SG6841

TYPICAL CHARACTERISTICS

S ta rt-up Current (I

25.5

25.0

24.5

24.0

23.5

23.0

22.5

Start-up Current (uA)

22.0

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

TEMPERATURE (

) vs Temperature

DD ST

℃℃℃℃

)

Frequency vs. FB Voltage

70

60

50

40

30

20

Frequency (KHz)

10

0

1.1 1.4 1.7 2 2.3 2.6 2.9

FB VOLTAGE (V)

Start-up Current (I

35

30

25

20

15

10

5

Start-up Current (uA)

0

0 2 4 6 8 10 12 14 16

) vs VDD Voltage

DD ST

VDD VOLTAGE (V)

Frequency in green mode (Fosc-green) vs

Temperature

10.52

10.50

10.48

10.46

10.44

10.42

10.40

10.38

Fosc-green (KHz)

10.36

10.34

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

TEMPERATURE (℃℃℃℃)

PWM O sci l lat or Frequency (Fosc) vs

Tempe r ature

64.4

64.3

64.2

64.1

64.0

Fosc (KHz)

63.9

63.8

63.7

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

TEMPERATURE (

)

℃℃℃℃

Max. Duty Cycle (%)

Maximum Duty Cycle DC(

MAX.

Tempe r ature

84.75

84.70

84.65

84.60

84.55

84.50

84.45

84.40

84.35

84.30

84.25

84.20

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

TEMPERATURE (

)

℃℃℃℃

)vs

©System General Corp. - 7 - www.sg.com.tw

Version 1.7 (IRO33.0001.B1) JUL.25,2003

Product Specification

High-integrated Green-mode PWM Controller SG6841

Min. Operating Voltage (V

DD(min)

) vs

Tempe r ature

10.20

10.15

10.10

10.05

(V)

10.00

9.95

9.90

DD(min)

V

9.85

9.80

9.75

9.70

-40 -25 -10 5 20 35 50 65 8 0 95 110 125

TEMPERATURE (

14

12

10

8

6

Ton (uS)

4

2

0

-2

0.620 0.628 0.636 0.644 0.652 0.660

RT Voltage vs Ton

RT VOLTAGE (V)

)

℃℃℃℃

Start Threshold Volta ge (V

TH(ON)

Temperature

16.6 0

16.5 5

16.5 0

16.4 5

(V)

16.4 0

TH(ON)

16.3 5

V

16.3 0

16.2 5

16.2 0

-40 -25 -10 5 2035 5065 80 95110 125

TEMPERATURE (

)

℃℃℃℃

Output Curre nt of pin R T (IRT) vs

Temperature

101.5

101.0

100.5

100.0

(uA)

RT

I

99.5

99.0

98.5

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

TEMPERATURE (℃℃℃℃)

) vs

V

0.63

0.62

(V)

0.61

OTP, STOP

0.61

V

0.60

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

vs Temperature

OTP, STOP

TEMPERATURE (

)

℃℃℃℃

0.84

0.79

0.74

0.69

SENSE

0.64

V

0.59

0.54

0.49

0.44

04080120 16 0 200 240 280 32 0 3 60

V

SENSE

I

VIN

vs I

(uA)

VIN

©System General Corp. - 8 - www.sg.com.tw

Version 1.7 (IRO33.0001.B1) JUL.25,2003

Product Specification

High-integrated Green-mode PWM Controller SG6841

OPERATION DESCRIPTION Start-up current

Typical start-up current is only 30uA so that a high resistance, and low-wattage, start-up resistor can be used to minimize power loss. For an AC/DC adapter with universal input range, a 1.5 MΩ, 0.25W, start-up resistor and a 10uF/25V VDD hold-up capacitor are enough for this application.

Operating current

Operating current has been reduced to 3mA. The low operating current enables a better efficiency and reduces the requirement of VDD hold-up capacitance.

Green Mode Operation

The patented green-mode function provides an off-time modulation to reduce the switching frequency in the light load and no load conditions. The on time is limited for better abnormal or brownout protection. V

,

FB

which is derived from the voltage feedback loop, is taken as the reference. Once V

is lower than the threshold

FB

voltage, switching frequency will be linearly decreased to the minimum green mode frequency around 10kHz (R

i

=26kΩ).

Oscillator Operation

A resistor from RI pin to ground will generate a constant current source for SG6841. This current is used to charge an internal capacitor and hence the internal clock and switching frequency are determined. Increase the resistance will decrease the current source and reduce the switching frequency. A 26kΩ resistor R 50uA constant current I

and generates 65kHz switching

i

creates a

i

frequency. The relation between Ri and switching freauency is:

1690

=

f

PWM

I

Ω

The range of the PWM oscillation frequency is designed as 50kHz ~ 90kHz.

)(kHz

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

)(kR

Current sensing and PWM current limiting

Peak current mode control is utilized in SG6841 to regulate output voltage and provide pulse by pulse current limiting. The switch current is detected by a sense resistor into the sense pin of SG6841. The PWM duty cycle is determined by this current sense signal and V

, the

FB

feedback voltage. When the voltage on sense pin reaches V

= (VFB–1.0)/3, a switch cycle will be terminated

COMP

immediately. V

is internally clamped to a variable

COMP

voltage around 0.85v for output power limit.

Leading Edge Blanking

Each time when the power MOSFET is switched on, a turn-on spike will inevitably occur on the sense-resistor. To avoid premature termination of the switching pulse, a 270 nsec leading-edge blanking time is built in. Conventional RC filtering can therefore be omitted. During this blanking period, the current-limit comparator is disabled and it cannot switch off the gate driver.

Under-voltage lockout (UVLO)

The turn-on and turn-off threshold of SG6841 are fixed internally at 16V/10V. During start-up, the hold-up capacitor must be charged to 16V through the start-up resistor so that SG6841 will be enabled. The hold-up capacitor will continue to supply V

before the energy

DD

can be delivered from auxiliary winding of the main transformer. V

must not drop below 10V during this

DD

start-up process. This UVLO hysteresis window insures that hold-up capacitor is adequate to supply V

during

DD

start-up.

Gate Output / Soft Driving

The SG6841 BiCMOS output stage is a fast totem pole gate driver. Cross conduction has been avoided to minimize heat dissipation, increases efficiency and enhances reliability. The output driver is clamped by an internal 18V Zener diode in order to protect power MOSFET transistors against undesirable gate over voltage. A soft driving waveform is implemented to minimize EMI.

Version 1.7 (IRO33.0001.B1) JUL.25,2003

Product Specification

High-integrated Green-mode PWM Controller SG6841

Built-in Slope Compensation

The sensed voltage across the current sense resistor is used for current mode control and pulse-by-pulse current limiting. Built-in slope compensation will improve stability or prevent sub-harmonic oscillation of peak current mode control. SG6841 inserts a

At high ambient temperature, Rntc will be smaller such that V (V

OTP,START

will decrease. When VRT is less than 0.65V

RT

), the PWM duty cycle will be decreased to lower the internal temperature of power supply. If the over heating situation still exists such that V further to 0.62V (V

), the PWM will be completely

OTP,STOP

decreases

RT

turned off.

synchronized positive-going ramp at every switching cycle. Vs-comp = 0.33V.

Limited Power Control

Const ant Output Power Limit

When the SENSE voltage, across the sense resistor Rs, reaches the threshold voltage, around 1.0V, the output GATE drive will be turned off after a small propagation delay t additional current proportional to t propagation delay is nearly constant regardless of the input line voltage V in a larger additional current and hence the output power limit is also higher than that under low input line voltage. To compensate this variation for wide AC input range, the threshold voltage is adjusted by the V VIN pin is connected to the rectified input line voltage through the start-up resistor, a higher line voltage will generate higher V threshold voltage is decreased if the V increased. Smaller threshold voltage, forces the output GATE drive to terminate earlier, thus reduce the total PWM turn-on time and make the output power equal to that of low line input. This proprietary internal compensation ensures a constant output power limit for wide AC input voltage from 90VAC to 264VAC.

. This propagation delay will introduce an

D

*Vin/Lp. Since the

D

Higher input line voltage will result

IN.

current. Since

IN

current into the VIN pin. The

IN

current is

IN

Every time when the output of power supply is shorted or over loaded, the FB voltage will increase. If the FB voltage is higher than a designed threshold, 4.2V, for longer than 31msec, the PWM output will then be turned off eternally. V decrease due to the supply current for SG6841. When V

, the supply voltage for SG6841, will

DD

is lower than the turn-off threshold such as 10V, SG6841 will be totally shut down. Due to the start up resistor, V

DD

will be charged up to the turn-on threshold voltage 16V until SG6841 is enabled again. If the over loading condition still exists, above protection will take place repeatedly. This will prevent the power supply from being overheated under over loading condition.

Noise immunity

Noise on the current sense or control signal may cause significant pulse width jitter, particularly in the continuous conduction mode. Slope compensation helps alleviate this problem. Good placement and layout practices should be followed. Avoiding long PCB traces and component leads, locating compensation and filter components near to the SG6841, and increasing the power MOS gate resistance will always help.

 Thermal Protection

An NTC thermistor Rntc in series with a resistor Ra can be connected from pin RT to ground. A constant current I can be expressed as V 2 x (1.3V / Ri).

Version 1.7 (IRO33.0001.B1) JUL.25,2003

is output from pin RT. The voltage on RT pin

RT

= IRT × (Rntc + Ra) in which IRT =

RT

Product Specification

High-integrated Green-mode PWM Controller SG6841

REFERENCE CIRCUIT Circuit

F1

2

C2

SG6841

4

R7

GATE

VDD

SENSE

THER2

BD1

1

R3

3

C4

R5

8

7

6

1

R10

R12

+

C9

1 2

D2

2 1

23

Q2

R8

D4

1,2

3

4

5 6,7

21

U2

4

C3

+

Q1

1

8,9

3 2

8,9

R4

C6

C7

1

23

R13

3

C10

R14

1

U3

R15

2

L3

1 2

+

R11

Vo+

+

C8

Vo+

21

D1

D3

2 1

R6

CN1

1 2 3

12

VZ1

THER1

1 2

3 4

L1

1 2

R1

3 4

L2

C1

1 2

R2

C5

U1

1

GND

2

FB

3

VIN

4 5

RI RT

R9

BOM

Reference Component Reference Component

BD1 BD 4A/600V R1,R2 R 1Mohm 1/4W

C1 XC 0.1uF/275V R3 R 100Kohm 1/2W

C2 XC 0.22uF/275V R4 R 47ohm 1/4W

C3 CC 0.01uF/500V R5,R7 R 750Kohm 1/4W

C4 EC 120u/400V R6 R 20Kohm 1/8W

C5 YC 222p/Y1 R8 R 0.3ohm 2W

C6 CC 1000pF/100V R9 R 33Kohm 1/ 8W

C7 CC 1000pF/50V R9 R 20Kohm 1/8W 1%

C8 EC 1000uF/35V R11 R 220ohm 1/8W

C9 EC 220uF/35V R12 R 4.7ohm 1/8W

D1 LED R13 R 6.8Kohm 1/8W

D2 Diode FR157 R14 R 154Kohm 1/8W

D3 ZD 18V R15 R 390Kohm 1/8W

D4 Diode FR102 THER1 Thermist or SCK054

F1 FUSE 4A/250V T1 Transformer

L1 900uH U1 IC SG6841

L2 15mH U2 IC PC817

Q1 Diode 20A100V U3 IC TL431

Q2 MOS 7A/600V VZ1 VZ 9G

Version 1.7 (IRO33.0001.B1) JUL.25,2003

Product Specification

High-integrated Green-mode PWM Controller SG6841

PACKAGE INFORMATION 8 PINS– DIP (D)

D

°

85

Θ

Dimension

E1

41

A2

A1

L

b1

e

b

E

A

eB

Symbol

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˚˚˚˚

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

Version 1.7 (IRO33.0001.B1) JUL.25,2003

Product Specification

High-integrated Green-mode PWM Controller SG6841

8 PINS– SOP (S)

85

E

1

4

b

e

D

A

A1

C

H

F

Θ

L

Dimension

Symbol

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 0.381 3.987 0.150 0.157 e 1.270 0.050 F H 5.791 6.197 0.228 0.244 L 0.406 1.270 0.016 0.050

θ˚˚˚˚ 0˚˚˚˚ 8˚˚˚˚ 0˚˚˚˚ 8˚˚˚˚

Version 1.7 (IRO33.0001.B1) JUL.25,2003

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

Product Specification

High-integrated Green-mode PWM Controller SG6841

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 the 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.

Version 1.7 (IRO33.0001.B1) JUL.25,2003