Datasheet SG6859A Datasheet (Fairchild)

August 2010

SG6859A

Low-Cost, Green-Mode PWM Controller for Flyback Converters

SG6859A — Low Cost, Green-Mode PWM Controller for Flyback Converters

Features



Green-Mode PWM

 Supports the “Blue Angel” Standard  Low Startup Current: 9μA  Low Operating Current: 3mA  300mA Driving Capability  Leading-Edge Blanking  Constant Output Power Limit  Universal Input  Built-in Synchronized Slope Compensation  Current-Mode Operation  Cycle-by-cycle Current Limiting  Under-Voltage Lockout (UVLO)  Programmable PWM Frequency with Frequency

Hopping

 V

Over-Voltage Protection (Auto Restart)

DD

 Gate Output Voltage Clamped at 17V  Low Cost  Few External Components Required  Small SSOT-6 Package

Applications

General-purpose switching mode power supplies and flyback power converters, such as:

 Battery chargers for cellular phones, cordless

phones, PDAs, digital cameras, and power tools

 Power adapters for ink jet printers, video game

consoles, and portable audio players

 Open-frame SMPS for TV/DVD standby and auxiliary

supplies, home appliances, and consumer electronics

 Replacements for linear transformers and RCC SMPS  PC 5V standby power

Description

This highly integrated PWM controller provides several enhancements designed to meet the low standby-power needs of low-power SMPS. 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 enables the power supply to meet even the strictest power conservation requirements.

The BiCMOS fabrication process enables reducing the startup current to 9μA and the operating current to 3mA. To further improve power conservation, a large startup resistance can be used. Built-in synchronized slope compensation ensures the stability of peak current mode control. Proprietary internal compensation provides a constant output power limit over a universal AC input range (90V limiting ensures safe operation during short-circuits.

To protect the external power MOSFET from damage by supply over voltage, the SG6859A’s output driver is clamped at 17V. SG6859A controllers can be used to improve the performance and reduce the production cost of power supplies. The best choice for replacing linear and RCC-mode power adapters, the SG6859A is available in 8-pin DIP and 6-pin SSOT-6 packages.

to 264VAC). Pulse-by-pulse current

AC

Ordering Information

Part Number Operating Temperature Range Package Packing Method

SG6859ATZ

SG6859ATY

SG6859ADZ

SG6859ADY (Preliminary)

-40 to +105°C

SSOT-6 Tape & Reel

DIP-8 Tube

Application Diagram

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters

Internal Block Diagram

Figure 1. Typical Application

Figure 2. Functional Block Diagram

Marking Information

*Marking for SG6859ATZ (Pb-free)

AAJFW

AAJF: SG6859A W

: Week Code A~Z=W1~W26 A

~Z=W27~W52

: Lead Free Package

XXXX: AAJF=SG6859A

T : Die Run Code

. . . . : Year Code

---: Week Code

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters

*Marking for SG6859ATY (Green Compound)

T: D=DIP P: Z= Lead Free + RoHS Compatible

Null=Regular Package XXXXXXXX: Wafer Lot Y: Year WW: Week V: Assembly Location

*Marking for SG6859ADZ (Pb-free)

F- Fairchild Logo

Z- Plant Code X- 1-Digit Year Code Y- 1-Digit Week Code TT: 2-Digit Die Run Code T: Package Type (D=DIP) P: Y: Green Package M: Manufacture Flow Code

*Marking for SG6859ADY (Green Compound)

Figure 3. Top Mark

Pin Configurations

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters

Figure 4. SSOT-6 Pin Configuration Figure 5. DIP-8 Pin Configuration

Pin Definitions

DIP

Pin #

SSOT

Pin #

1 6 GATE The totem-pole output driver for driving the power MOSFET.

2 5 VDD Power supply

3 NC No connection

4 4 SENSE

5 3 RI

6 NC No connection

7 2 FB

8 1 GND Ground

Name Description

Current sense. This pin senses the voltage across a resistor. When the voltage reaches the internal threshold, PWM output is disabled. This activates over-current protection. This pin also provides current amplitude information for current-mode control.

A resistor connected from the RI pin to ground generates a constant current source used to charge an internal capacitor and determine the switching frequency. Increasing the resistance reduces the amplitude of the current source and the switching frequency. A 95kΩ resistor R 70kHz switching frequency.

Feedback. The FB pin provides the output voltage regulation signal. It provides feedback to the internal PWM comparator, so that the PWM comparator can control the duty cycle.

results in a 50μA constant current II and a

I

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters

Absolute Maximum Ratings

Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only.

Symbol Parameter Min. Max. Unit

V

DC Supply Voltage

VDD

VFB Input Voltage to FB Pin -0.3 7.0 V

V

Input Voltage to Sense Pin -0.3 7.0 V

SENSE

TJ Operating Junction Temperature 150

ΘJA

T

STG

Thermal Resistance (Junction-to-Air)

Storage Temperature Range -55 +150

TL Lead Temperature (Wave Soldering or IR, 10 Seconds) +260

Electrostatic Discharge Capability, Human Body Model JESD22-A114 3.5 kV

ESD

Electrostatic Discharge Capability, Charged Device Model JESD22-C101 1.5 kV

Electrostatic Discharge Capability, Machine Model, JESD22-A115 200 V

Notes:

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

2. Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.

(1, 2)

30 V

°C

SSOT 273

DIP 113

°C/W

°C

Electrical Characteristics

Unless otherwise noted, VDD=15V and TA=25°C.

Symbol Parameter Conditions Min. Typ. Max. Units

VDD Section

V

Continuously Operation Voltage 22 V

DD-OP

V

Turn-on Threshold Voltage 15.5 16.5 17.5 V

DD-ON

V

Turn-off Threshold Voltage 8.5 9.5 10.5 V

DD-OFF

I

Startup Current VDD=V

DD-ST

I

Operating Supply Current

DD-OP

V

VDD Over-Voltage Protection Level Auto Restart 24 25 26 V

DD-OVP

t

D-VDDOVP

V

VDD Over-Voltage Protection Debounce Auto Restart 125 μs

Low-Threshold Voltage to Exit

V

DD

DD-G OFF

Green-off Mode

V

=15V, CL=1nF

DD

Feedback Input Section

ZFB Input Impedance 5 kΩ

V

FB Output High Voltage 5 V

FB-OPEN

V

FB Open-loop Trigger Level 4.3 4.6 4.9 V

FB-OL

t

Delay of FB Pin Open-loop Protection 56 ms

D-OLP

V

Green-Mode Entry FB Voltage 2.60 2.85 3.10 V

FB-N

V

Green-Mode Ending FB Voltage 2.2 V

FB-G

SG Green-Mode Modulation Slope RI=95kΩ 40 75 100 Hz/mV

Current-Sense Section

Z

Input Impedance 10 kΩ

SENSE

tPD Delay to Output 40 55 100 ns

V

Flat Threshold Voltage for Current Limit 1 V

STHFL

V

Valley Threshold Voltage for Current Limit 0.75 0.80 0.85 V

STHVA

t

Leading-Edge Blanking Time

LEB

DCY

Duty Cycle of SAW Limit 40 %

SAW

Oscillator Section

Center Frequency

f

Frequency

OSC

T

Hopping Period RI=95kΩ 3.7 ms

HOP

f

Green-Mode Frequency RI=95kΩ 20 kHz

OSC-G

Hopping Range

RI=95kΩ

fDV Frequency Variation vs. VDD Deviation VDD=13.5 to 22V 0 0.02 2.00 %

fDT Frequency Variation vs. Temp. Deviation TA=-20 to 85°C 2 %

Output Section

DCY

V

Maximum Duty Cycle 62 67 72 %

MAX

V

Output Voltage Low VDD=15V, IO=20mA 1.4 V

GATE-L

Output Voltage High VDD=13.5V, IO=20mA 8 V

GATE-H

tr Rising Time VDD=15V, CL=1nF 150 ns

tf Falling Time VDD=15V, CL=1nF 55 ns

V

GATE-CLAMP

Output Clamp Voltage VDD=22V 16 17 18 V

– 0.1V 9 15 μA

DD-ON

3.0 3.5 mA

V

DD-

+ 1

OFF

270 320 370 ns

65 70 75

±4.9

kHz

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters

V

Typical Performance Characteristics

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters

17.0

16.8

16.6

(V)

DD-ON

16.4

V

16.2

16.0

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

Temperature (℃)

Figure 6. Turn-on Threshold Voltage (V

vs. Temperature

3.0

2.5

2.0

(μA)

DD-ST

1.5

I

DD-ON

)

13.0

12.0

11.0

(V)

DD-OFF

10.0

V

9.0

8.0

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

Temperature (℃)

Figure 7. Turn-off Threshold Voltage (V

vs. Temperature

3.5

3.3

3.1

(mA)

2.9

DD-OP

I

DD-ON

)

1.0

0.5

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

Figure 8. Startup Current (I

Temperature (℃)

DD-ST

) vs. Temperature Figure 9. Operating Supply Current (I

70.0

69.0

68.0

(KHz)

OSC

67.0

F

66.0

65.0

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

Figure 10. Center Frequency (f

Temperature (℃)

OSC

) vs. Temperature Figure 11. Maximum Duty Cycle (DCY

2.7

2.5

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

Temperature (℃)

vs. Temperature

70.0

69.0

68.0

(%)

MAX

67.0

DCY

66.0

65.0

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

Temperature (℃)

vs. Temperature

DD-OP

MAX

)

Typical Performance Characteristics

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters

3.2

3.0

2.8

(V)

FB-N

V

2.6

2.4

2.2

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

Temperature (℃)

Figure 12. Green-Mode Entry FB Voltage (V

vs. Temperature

350.0

330.0

310.0

(ns)

LEB

t

290.0

FB-N

)

3.0

2.8

2.6

(V)

FB-G

V

2.4

2.2

2.0

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

Temperature (℃)

Figure 13. Green-Mode Ending FB Voltage (V

vs. Temperature

3.5

3.0

2.5

(mA)

DD-OP

2.0

I

FB-G

)

270.0

250.0

-40-25-10 5 203550658095110125

Temperature (℃ )

Figure 14. Leading-Edge Blanking Time (t

vs. Temperature

LEB

)

1.5

1.0 12 13 14 15 16 17 18 19 20 21 22 23 24

VDD (V)

Figure 15. Operating Supply Current vs.

VDD Voltage

Operation Description

SG6859A devices integrate many useful designs into one controller for low-power, switch-mode power supplies. The following descriptions highlight some of the features of the SG6859A series.

Startup Current

The startup current is only 9μA. Low startup current allows a startup resistor with high resistance and lowwattage to supply the startup power for the controller. A

1.5MΩ, 0.25W, startup resistor and a 10µF/25V V hold-up capacitor are sufficient for an AC-to-DC power adapter with a wide input range (100V

to 240VAC).

AC

Operating Current

The operating current has been reduced to 3mA. The low operating current results in higher efficiency and reduces the V

hold-up capacitance requirement.

DD

Green-Mode Operation

The proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. On-time is limited to provide stronger protection against brownouts and other abnormal conditions. The feedback current, which is sampled from the voltage feedback loop, is taken as the reference. Once the feedback current exceeds the threshold current, the switching frequency starts to decrease. This green-mode function dramatically reduces power consumption under light-load and zeroload conditions. Power supplies using the SG6859A can meet even the strictest regulations regarding standby power consumption.

Oscillator Operation

A resistor connected from the RI pin to ground generates a constant current source used to charge an internal capacitor. The charge time determines the internal clock speed and the switching frequency. Increasing the resistance reduces the amplitude of the input current and the switching frequency. A 95kΩ R resistor results in a 50µA constant current, I

, and a

I

70kHz switching frequency. The relationship between R and the switching frequency is:

6650

=

PWM

f

Ω

I

The recommended f

(1)

(kHz)

)(kR

is from 50kHz to 80kHz.

PWM

Leading-Edge Blanking

Each time the power MOSFET is switched on, a turn-on spike occurs at the sense-resistor. To avoid premature termination of the switching pulse, a 320ns leadingedge blanking time is built in. Conventional RC filtering can be omitted. During this blanking period, the currentlimit comparator is disabled and cannot switch off the gate driver.

Constant Output Power Limit

When the SENSE voltage across the sense resistor, R

, reaches the threshold voltage (around 1V), the

S

DD

I

output GATE drive is turned off following a short propagation delay, t

. This propagation delay

PD

introduces an additional current proportional to t

PD•VIN/LP

regardless of the input line voltage V

. The propagation delay is nearly constant,

. Higher input line

IN

voltages result in larger additional currents. At high input line voltages, the output power limit is higher than at low input line voltages. To compensate for this output power limit variation across a wide AC input range, the threshold voltage is adjusted by adding a positive ramp. This ramp signal rises from 0.8V to 1V, then flattens out at 1V. A smaller threshold voltage forces the output GATE drive to terminate earlier, which reduces the total PWM turn-on time and makes the output power equal to that of low line input. This proprietary internal compensation ensures a constant output power limit for a wide AC input voltage range (90V

to 264VAC).

AC

Under-Voltage Lockout (UVLO)

The turn-on and turn-off thresholds are fixed internally at 16.5V and 9.5V. During startup, the hold-up capacitor must be charged to 16.5V through the startup resistor to enable the SG6859A. The hold-up capacitor continues to supply VDD until power can be delivered from the auxiliary winding of the main transformer. V

must not

DD

drop below 9.5V during this startup process. This UVLO hysteresis window ensures that hold-up capacitor is adequate to supply V

during startup.

DD

Gate Output

The BiCMOS output stage is a fast totem pole gate driver. Cross conduction has been avoided to minimize heat dissipation, increase efficiency, and enhance reliability. The output driver is clamped by an internal 17V Zener diode to protect power MOSFET transistors against undesired over-voltage gate signals.

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 improves stability and prevents sub-harmonic oscillations due to peak-current mode control. The SG6859A has a synchronized, positively-sloped ramp built-in at each switching cycle. The slope of the ramp is:

Duty0.36 ×

Duty(max.)

Noise Immunity

Noise from the current sense or the control signal can cause significant pulse-width jitter, particularly in continuous-conduction mode (CCM). While slope compensation helps alleviate these problems, further precautions should still be taken. Good placement and layout practices should be followed. Avoiding long PCB traces and component leads, locating compensation and filter components near the SG6859A, and increasing power MOS gate resistance improve performance.

(2)

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters

Applications Information

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters

F1

L

CX1

N

C6

1

BD1

2

3

U1

1

GND

2

FB

RI3SENSE

R9

1 2

4

C1

GATE

VDD

L1

C3

R5 R4

D1

23 2 1

Q1

R6

D2

R3

21

T1

10

9

8 5

7 3,4

U2

3 4

1,2

CY1

2 1

12

C8

U3

2 3

L2

1 2

D5

2 1

R14

1

VO

C9

GND

R13

C10

R12

D4

R10

C7

R11

R1

C2

R2

R7

6

5

4

1

R15

C11

R8

C4

Figure 16. Reference Circuit

Bill of Materials (BOM)

Reference Component Reference Component

BD1 BD 1A/500V L2 10µH 6mm

CX1 (Optional) XC 0.1μF Q1 MOSFET 1A/600V

CY1 (Optional) YC 1nF/400V (Y1) R1,R2 R 750KΩ 1206

C1 CC 10nF/500V R3,R4 R 47KΩ 1206

C2 EC 10μF/400V 105°C R5 R 47Ω 1206

C3 CC 1nF/500V R6 R 4.7Ω 1206

C4 EC 10μF/50V R7 R 100Ω 0805

C6 CC 4.7nF 0805 R8 R 10Ω 1206

C7 (Optional) CC 1nF/100V 1206 R9 R 100KΩ 0805

C8 EC 470μF/10V 105°C R10 (Optional) R 10Ω 1206

C9 EC 220μF/10V 105°C R11 R 100Ω 1/8W

C10 CC 2.2nF 0805 R12 R 33KΩ 0805

C11 N.C. R13 R 33KΩ 1/8W

D1 Diode FRI07 R14 R 4.7KΩ 0805

D2 Diode FR102 R15 R 0Ω 0805

D4 Diode SB360 T1 EE-16

D5 (Optional) ZD 6.8V 0.5W U1 IC SG6859A

F1 R 1Ω/0.5W U2 PC817

L1 20mH 6•8mm U3 TL431

Physical Dimensions

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters

9.83

9.00

6.67

6.096

8.255

7.61

3.60

3.00

3.683

3.20

0.356

0.20

5.08 MAX

0.33 MIN

(0.56)

2.54

0.56

0.355

1.65

1.27

7.62

NOTES: UNLESS OTHERWISE SPECIFIED A) THIS PACKAGE CONFORMS TO

JEDEC MS-001 VARIATION BA

B) ALL DIMENSIONS ARE IN MILLIMETERS.

C) DIMENSIONS ARE EXCLUSIVE OF BURRS,

MOLD FLASH, AND TIE BAR EXTRUSIONS.

D) DIMENSIONS AND TOLERANC

ES PER

ASME Y14.5M-1994

E) DRAWING FILENAME AND REVSION: MKT-N08FREV2.

Figure 17. 8-Pin, Dual Inline Package (DIP)

7.62

9.957

7.87

Package drawings are provided as a service to customers considering Fairchild components. Draw i ngs may change in any manner without notice. Pl ease note the revision and/or date on the drawing and contact a Fairchild Semic onductor representative to verify or obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products.

Always visi t Fai rchild Semiconductor’s online packaging area for the most recent package drawings:

http://www.fairchildsemi.com/packaging/

.

Physical Dimensions (Continued)

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters

Figure 18. 6-Pin, SSOT-6 Package

Package drawings are provided as a service to customers considering Fairchild components. Draw i ngs may change in any manner without notice. Pl ease note the revision and/or date on the drawing and contact a Fairchild Semic onductor representative to verify or obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products.

Always visi t Fai rchild Semiconductor’s online packaging area for the most recent package drawings:

http://www.fairchildsemi.com/packaging/

.

SG6859A — Low-Cost, Green-Mode PWM Controller for Flyback Converters