FAN6791_技术文档

April 2009

FAN6791 / FAN6793

Highly Integrated, Dual-PWM Combination Controller

Features

Description

The highly integrated FAN6791/3 dual PWM

combination controller provides several features to

enhance the performance of converters.

High-Voltage Startup

Low Operating Current

Interleaved Stand-by PWM / Forward PWM Switching

Green Mode Stand-by PWM / Forward PWM

To minimize standby power consumption, a proprietary

green-mode function provides off-time modulation to

linearly decrease the switching frequency at light-load

conditions. To avoid acoustic-noise problems, the

minimum PWM frequency is set above 20KHz. This

green-mode function enables the power supply to meet

international power conservation requirements. With the

internal high-voltage startup circuitry, the power loss

due to bleeding resistors is also eliminated. To further

Linearly Decreasing Stand-by PWM Frequency to

20kHz

Remote On / Off

AC Brownout Protection

Forward PWM with Soft-Start

Frequency Hopping to Reduce EMI Emissions

reduce

power

consumption,

FAN6791/3

is

manufactured using the CMOS process, which allows

an operating current of only 6mA.

Cycle-by-Cycle Current Limiting for Stand-by PWM /

Forward PWM

FAN6791/3 integrates

a frequency-jittering function

internally to reduce EMI emissions of a power supply

with minimum line filters. The built-in synchronized slope

compensation achieves stable peak-current-mode

control. The proprietary internal line compensation

ensures constant output power limit.

Leading-Edge Blanking for Stand-by PWM / Forward

PWM

Synchronized Slope Compensation for Stand-by

PWM / Forward PWM

GATE Output Maximum Voltage Clamp

V_DDOver-Voltage Protection (OVP)

V_DDUnder-Voltage Lockout (UVLO)

FAN6791/3 provides many protection functions,

including brownout protection, cycle-by-cycle current

limiting, and an internal open-loop protection circuit to

ensure safety should an open-loop or output short-

circuit failure occur. PWM output is disabled until V_DD

drops below the UVLO lower limit when the controller

restarts. As long as V_DDexceeds ~24.5V, the internal

OVP circuit is triggered.

Internal Open-Loop Protection for Stand-by PWM /

Forward PWM

Constant Power Limit for Stand-by PWM / Forward

PWM

Applications

General-purpose switch-mode power supplies and

flyback power converters, including:

PC-ATX Power Supplies

FAN6791 / FAN6793 • Rev. 1.0.2

www.fairchildsemi.com

Ordering Information

Part

Number

OPWM

Operating

Packing

Method

Package

Eco Status

Green

Maximum Duty Temperature Range

16-pin Dual In-Line

Package (DIP)

FAN6791NY

FAN6793NY

FAN6791MY

FAN6793MY

48%

65%

48%

65%

-40°C to +105°C

Tube

16-pin Dual In-Line

Package (DIP))

Green

Tube

16-pin Small Out-Line

Package (SOP)

Green

Tape & Reel

16-pin Small Out-Line

Package (SOP)

Green

For Fairchild’s definition of “green” Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.

Application Diagram

Figure 1. Typical Application

FAN6791 / FAN6793 • Rev. 1.0.2

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2

Block Diagram

Pattern

Generator

Figure 2. Function Block Diagram

FAN6791 / FAN6793 • Rev. 1.0.2

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3

Marking Information

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 (N:DIP, M:SOP)

P – Y: Green Package

M – Manufacture Flow Code

Figure 3. Top Mark

Pin Configuration

Figure 4. Pin Configuration (Top View)

FAN6791 / FAN6793 • Rev. 1.0.2

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4

Pin Definitions

Pin # Name Description

For startup, this pin is pulled HIGH to the line input or bulk capacitor via resistors.

1

2

3

HV

NC

No connection.

Ground.

GND

Oscillator Setting. One resistor connected between RI and ground pins determines the switching

frequency (resistance between 12 ~ 47kΩ is recommended). The switching frequency is equal to

[1560 / RI]kHz, where RI is in kΩ. For example, if RI is equal to 24kΩ, then the switching frequency

is 65kHz.

4

RI

Voltage Feedback for Flyback PWM Stage. It is internally pulled HIGH through a 6.5kΩ resistor.

An external opto-coupler from secondary feedback circuit is usually connected to this pin.

5

6

7

FBFYB

IFYB

PWM Current Sense for Flyback PWM Stage. The sensed voltage is used for peak-current-

mode control and cycle-by-cycle current limiting.

Voltage Feedback for Forward PWM Stage. It is internally pulled HIGH through a 6.5kΩ resistor.

An external opto-coupler from secondary feedback circuit is usually connected to this pin.

FBPWM

PWM Current Sense for Forward PWM Stage. Via a current sense resistor, this pin provides the

control input for peak-current-mode control and cycle-by-cycle current limiting.

8

9

IPWM

VREF

Reference voltage. This pin can provide a reference voltage 5V.

PWM Soft-Start. During startup, the SS pin charges an external capacitor with a 20µA constant

current source. The voltage on FBPWM is clamped by SS during startup. In the event of a

protection condition occurring and/or forward PWM being disabled, the SS pin quickly discharges.

10

SS

PWM Remote ON/OFF. Active HIGH. The forward PWM is disabled whenever the voltage at this

pin is lower than 0.8V or the pin is open.

11

12

13

ON/OFF

PGND

Ground. The power ground.

Forward PWM Gate Drive. The totem-pole output drive for the forward PWM MOSFET. This pin is

internally clamped under 16V to protect the MOSFET.

OPWM

Power Supply. The internal protection circuit disables PWM output as long as V_DDexceeds the

OVP trigger point.

14

15

16

VDD

OFYB

VRMS

Flyback PWM Gate Drive. The totem-pole output drive for the forward PWM MOSFET. This pin is

internally clamped under 16V to protect the MOSFET.

Line-Voltage Detection. The pin is used for line compensation, for forward, and brownout

protection.

FAN6791 / FAN6793 • Rev. 1.0.2

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5

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. All voltage values, except differential voltage, are given with

respect to GND pin. Stresses beyond those listed under “absolute maximum ratings “may cause permanent damage

to the device.

Symbol

Parameter

Min.

Max.

Unit

V_DD

V_HV

V_HIGH

V_LOW

P_D

DC Supply Voltage

27

500

27.0

7.0

V

Input Voltage to HV Pin

OPWM, OFYB, ON/OFF

Others

-0.3

V

Power Dissipation (T_A< 50°C)

Operating Junction Temperature

Storage Temperature Range

°C/W

°C

800

+125

T_J

-40

-55

T_STG

R_{Θ j-a}

+150

82.5

Thermal Resistance (Junction-to-Case)

°C/W

°C

T_L

Lead Temperature (Wave Soldering, 10 Seconds)

+260

3.5

Human Body Model , JEDEC:JESD22-A114

(All Pins Except HV Pin)

ESD

kV

Charged Device Model , JEDEC:JESD22-C101

(All Pins Except HV Pin)

1.5

Recommended Operating Conditions

The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended

operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not

recommend exceeding them or designing to Absolute Maximum Ratings.

Symbol

Parameter

Operating Ambient Temperature

Min.

Max.

Unit

T_A

-40

+105

°C

FAN6791 / FAN6793 • Rev. 1.0.2

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6

Electrical Characteristics

V_DD=18V; R_I=24kΩ;T_A=25°C, unless noted.

Symbol

V_DDSection

V_DD-OP

Parameter

Conditions

Min.

Typ.

Max.

Units

Continuously Operating Voltage

Startup Current

22

50

10

V

I_{DD ST}

V_DD– 0.16V

10

6

μA

mA

I_DD-OP1

Operating Current 1

V_DD=15V, GATE Open

V_DD=15V, GATE Open,

_REF=10mA

I_DD-OP2

Operating Current 2

16

20

I

V_TH-ON

V_TH-OFF

V_TH-OLP

I_TH-OLP

Start Threshold Voltage

Minimum Operating Voltage

I_DD-OLPOff Voltage

15

9

16

10

7.5

80

17

11

V

6.5

70

8.0

100

V

Internal Sink Current

V_TH-OLP+0.1V

V_DD-OVP=26V

μA

V

V_DDOver-voltage Protection

(Turn Off PWM with Delay)

V_DD-OVP

23.4

80

24.5

100

25.5

120

V_DDOver-Voltage Protection

Debounce

μs

t_OVP

HV

V_AC=90V(V_DC=120V),

V_DD=10µF

I_D

Maximum Input Current

Internal Current Source

1.5

2.5

10

3.5

50

mA

I_HV-CS

HV=500V,V_DD=15V

μA

Oscillator and Green-Mode Operation

V_RI

RI Voltage

1.176

62

1.200

65

1.224

68

V

Center Frequency,

R_I=24kΩ

f_OSC

Normal PWM Frequency

kHz

Jitter Range

±3.7

18

±4.2

20

±4.7

22

Minimum Frequency in Green

Mode

f_OSC-G-MIN

RI

R_I=24kΩ

kHz

kΩ

RI Range

12

24

47

If RI > RI_OPEN, PWM

Turned Off

RI_OPEN

RI Pin Open Protection

1

MΩ

If RI > RI_SHORT, PWM

Turned Off

RI_SHORT

RI Pin Short Protection

6

kΩ

V_RMSfor AC Brownout Protection

Off Threshold Voltage for AC

Brownout Protection

V_RMS-OFF

V_RMS-ON

t_RMS

0.75

0.80

0.85

V

Start Threshold Voltage for AC

Brownout Protection

V_RMS-UVP-1V_RMS-UVP-1V_RMS-UVP-1

+0.17

+0.19

+0.21

AC Brownout Protection

Debounce Time

R_I=24kΩ

150

195

240

ms

VREF

V_REF

Reference Voltage

I_REF=1mA, C_REF=0.1µF

4.75

5.00

5.25

80

V

Load Regulation of Reference

Voltage

C_REF=0.1µF,

△V_REF1

mV

I_REF=1mA to 10mA

Line Regulation of Reference

Voltage

C_REF=0.1µF,

V_DD=12V to 22V

△V_REF2

25

mV

I_{REF_MAX}

I_OS

Maximum Current

10

15

25

mA

Output Short Circuit

20

FAN6791 / FAN6793 • Rev. 1.0.2

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7

Electrical Characteristics

V_DD=18V; R_I=24kΩ;T_A=25°C, unless noted.

Symbol

Parameter

Conditions

Min.

Typ.

Max.

Units

ON/OFF

R_ON/OFF

Impedance ON/OFF Pin

50

100

3.6

kΩ

High Threshold Level of

Synchronizing Signal

V_ON

2.4

3.0

1.0

V

Low Threshold Level of

Synchronizing Signal

V_OFF

0.8

1.2

V

Over Temperature Protection (OTP)

Protection Junction

T_Off

130

100

140

110

+150

+120

°C

Temperature⁽¹⁾

T_Restart

Restart Junction Temperature⁽²⁾

Flyback PWM Stage

FBFYB Feedback Input

FB Input to Current Comparator

Attenuation

A_V-FLY

1/3.75

1/3.20

1/2.75

7

V/V

Z_FB

V_HGH

V_FB-OLP

t_OLP

Input Impedance

4

5

kΩ

Output High Voltage

FB Pin Open

5.0

4.2

53

5.2

4.5

56

V

FB Open-Loop Trigger Level

FB Open-Loop Protection Delay

Green Mode Entry FB Voltage

Slope of Green-Mode Modulation

Green Mode Ending FB Voltage

4.8

59

ms

V

V_N

2.4

60

2.5

75

2.6

90

S_G

Hz/mV

V

V_G

1.8

1.9

2.0

V_FBPWMfor Zero Duty Cycle

(Forward Turn On)

V_OZ-OFYB

1.2

1.3

1.4

V

IFYB Current Sense

Z_CS

Input Impedance

12

kΩ

Peak Current Limit Threshold

Voltage 1

V_LIMIT1

V_RMS=1V

0.75

60

0.80

0.85

120

V

Peak Current Limit Threshold

Voltage 2

V_LIMIT2

t_PD

V_RMS=1.5V

V_LIMIT1-0.1

V

Propagation Delay to GATE

Output

V_DD=15V, OFYB Drops

to 9V

ns

t_BNK

Leading-Edge Blanking Time

Slope Compensation

200

270

350

ns

V

Duty=DCY_MAX

0.34

0.37

0.41

ΔV_SLOPE

Threshold Voltage for SENSE

Short-Circuit Protection

V_S-SCP

t_D-SSCP

0.1

0.15

180

0.2

V

Delay Time for SENSE Short-

Circuit Protection

V_SENSE<0.15V,

R_I=24KΩ

100

240

µs

OFYB-GATE Driver

Flyback PWM Gate Output

V_OFYB-CLAMP

V_DD=22V

16

18

V

Clamping Voltage

Output Voltage Low

Output Voltage High

V_OL-OFYB

V_OH-OFYB

V_DD=15V; I_O=20mA

V_DD=12V; I_O=20mA

1.5

V

8

V_DD=15V; Gate=1nF;

Gate=2~9V

t_R-OFYB

t_F-OFYB

Rising Time

Falling Time

30

60

120

ns

V_DD=15V; Gate=1nF;

Gate=9~2V

30

60

50

65

90

70

ns

%

DCY_MAX-OFYBMaximum Duty Cycle

FAN6791 / FAN6793 • Rev. 1.0.2

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Electrical Characteristics

V_DD=18V; R_I=24kΩ;T_A=25°C, unless noted.

Symbol

Parameter

Conditions

Min.

Typ.

Max.

Units

Forward PWM Stage

FBPWM-Feedback Input

FB to Current Comparator

Attenuation

A_V

1/3.2

1/2.7

1/2.2

7

V/V

Z_FB

Input Impedance

Output High Voltage

4

5

kΩ

V_HGH

FB Pin Open

5.0

5.2

V

PWM Open-Loop Protection

Voltage

V_OPEN-PWM

4.2

4.5

4.8

V

t_OPEN-PWM-Interval of PWM Open-Loop

R_I=24kΩ

500

600

700

ms

Protection Reset

HICCUP

PWM Open-Loop Protection

Delay Time

t_OPEN-PWM

80

95

120

1.4

ms

V

V_OZ-OPWM

V_FBPWMfor Zero Duty Cycle

1.2

1.3

IPWM-Current Sense

Propagation Delay to Output –

V_LIMITLoop

V_DD=15V, OPWM

Drops to 9V

t_PD

60

120

ns

V

Peak Current Limit Threshold

Voltage 1

V_LIMIT1

V_RMS=1V

0.75

0.80

0.85

Peak Current Limit Threshold

Voltage 2

V_LIMIT2

t_BNK

V_RMS=1.5V

V_LIMIT1-0.1

350

V

Leading-Edge Blanking Time

270

450

ns

Slope Compensation

ΔV_s=ΔV_SLOPEx (t_on/t)

ΔV_s: Compensation Voltage

Added to Current Sense

0.40

0.45

16

0.55

V

ΔV_SLOPE

OPWM-GATE Driver

Output Voltage Maximum

(Clamp)

V_OPWM-CLAMP

V_DD=22V

18

V

V_OL

V_OH

Output Voltage Low

Output Voltage High

V_DD=15V; I_O=100mA

V_DD=13V; I_O=100mA

1.5

V

8

V_DD=15V; C_L=5nF;

O/P=2V to 9V

t_R

t_F

Rising Time

Falling Time

30

60

50

120

110

ns

V_DD=15V; C_L=5nF;

O/P=9V to 2V

30

FAN6791 Maximum Duty Cycle

FAN6793 Maximum Duty Cycle

47

60

48

65

49

70

DCY_MAX-OPWM

%

R_I=24kΩ

Soft Start

Constant Current Output for

Soft-Start

I_SS

17

20

23

µA

R_I=24kΩ

R_D

Discharge Resistance

470

564

Ω

Notes:

1. When activated, the output is disabled and the latch is turned off.

2. This is the threshold temperature for enabling the output again and resetting the latch after over-temperature

protection has been activated.

FAN6791 / FAN6793 • Rev. 1.0.2

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Typical Characteristics

10.0

9.0

8.0

7.0

6.0

5.0

4.0

3.0

2.0

1.0

0.0

10.0

9.0

8.0

7.0

6.0

5.0

4.0

3.0

2.0

1.0

0.0

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

Figure 5. Startup Current I_DD-STvs. Temperature

Figure 6. I_DD-OP1vs. Temperature

20.0

19.0

18.0

17.0

16.0

15.0

14.0

13.0

12.0

11.0

2.5

2.0

1.5

1.0

0.5

0.0

10.0

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

Figure 7. I_DD-OP2vs. Temperature

Figure 8. I_D-MAXvs. Temperature

16.2

16.1

16.0

15.9

15.8

15.7

15.6

10.2

10.1

10.0

9.9

9.8

9.7

9.6

9.5

9.4

9.3

9.2

15.5

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

Figure 9. V_DD-ONvs. Temperature

Figure 10. V_DD-OFFvs. Temperature

47.50

47.45

47.40

47.35

47.30

47.25

47.20

47.15

64.4

64.3

64.2

64.1

64.0

63.9

63.8

63.7

63.6

63.5

63.4

63.3

47.10

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

Figure 11. OPWM Maximum Duty Cycle

vs. Temperature

Figure 12. OFYB Maximum Duty Cycle

vs. Temperature

FAN6791 / FAN6793 • Rev. 1.0.2

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10

Typical Characteristics

32.10

32.05

32.00

31.95

31.90

31.85

31.80

31.75

57.5

57.0

56.5

56.0

55.5

55.0

54.5

54.0

53.5

31.70

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

Figure 13. Rising Time t_R-OPWMvs. Temperature

Figure 14. Falling Time t_F-OPWMvs. Temperature

27.4

27.2

27.0

26.8

26.6

26.4

26.2

26.0

39

38

37

36

35

34

33

32

31

25.8

30

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

Figure 15. Rising Time t_R-OFYBvs. Temperature

Figure 16. Falling Time t_F-OFYBvs. Temperature

0.802

0.800

0.798

0.796

0.794

0.792

0.790

0.667

0.666

0.665

0.664

0.663

0.662

0.661

0.660

0.788

0.659

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

Figure 17. I_PWM-VLIMIT(V_RMS=1V) vs. Temperature

Figure 18. I_PWM-VLIMIT(V_RMS=1.5V) vs. Temperature

0.815

0.810

0.805

0.800

0.795

0.790

0.785

0.653

0.652

0.651

0.650

0.649

0.648

0.647

0.646

0.645

0.644

0.780

0.643

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

Figure 19. I_FYB-VLIMIT(V_RMS=1V) vs. Temperature

Figure 20. I_FYB-VLIMIT(V_RMS=1.5V)vs. Temperature

FAN6791 / FAN6793 • Rev. 1.0.2

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11

Typical Characteristics

66.1

66.0

65.9

65.8

65.7

65.6

66.3

66.2

66.1

66.0

65.9

65.8

65.7

65.6

65.5

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

Figure 21. OPWM Frequency vs. Temperature

Figure 22. OFYB Frequency vs. Temperature

FAN6791 / FAN6793 • Rev. 1.0.2

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12

Functional Description

The highly integrated FAN6791 / FAN6793 dual-PWM

combination controller provides several features to

enhance the performance of converters.

Proprietary interleave switching synchronizes the

flyback and forward PWM stages. This reduces

switching noise.

The proprietary frequency jittering function for the

flyback and forward PWM stages helps reduce

switching EMI emissions.

Figure 23. Oscillation Frequency in Green Mode

For the flyback and forward PWM, the synchronized

slope compensation ensures the stability of the current

loop under continuous-mode operation. In addition,

FAN6791/3 provides complete protection functions,

such as brownout protection and RI open/short.

Line Voltage Detection (V_RMS

)

Figure 24 shows a resistive divider with low-pass

filtering for line-voltage detection on VRMS pin. The

V_RMSvoltage is used for the PFC multiplier and

brownout protection. For brownout protection, when the

V_RMSvoltage drops below 0.8V, OPFC turns off.

Startup Current

For startup, the HV pin is connected to the line input or

bulk capacitor through external resistor RHV,

recommended as 100KΩ. Typical startup current drawn

from pin HV is 2mA and it charges the hold-up capacitor

through the resistor RHV. When the V_DDcapacitor level

reaches V_DD-ON, the startup current switches off. At this

moment, the V_DDcapacitor only supplies the FAN6791/3

to maintain the V_DDbefore the auxiliary winding of the

main transformer provides the operating current.

Oscillator Operation

A resistor connected from the RI pin to the GND pin

generates a constant current source for the FAN6791/3

controller. This current is used to determine the center

PWM frequency. Increasing the resistance reduces

PWM frequency. Using a 24KΩ resistor results in a

corresponding 65kHz PWM frequency. The switching

frequency is programmed by the resistor R_Iconnected

between RI pin and GND. The relationship is:

Figure 24. Line-Voltage Detection on VRMS Pin

Remote On/Off

Figure 25 shows the remote on / off function. When the

supervisor FPO pin pulls down and enables the system

by connecting an opto-coupler, V_REFapplies to the

ON/OFF pin to enable forward PWM stage.

1560

f_PWM

=

(kHz)

(1)

R_I(kΩ)

The range of the PWM oscillation frequency is designed

as 33KHz ~ 130KHz. FAN6791/3 integrates frequency

hopping function internally. The frequency variation

ranges from around 61KHz to 69KHz for a center

frequency 65KHz. The frequency hopping function helps

reduce EMI emission of a power supply with minimum

line filters.

For power saving, flyback PWM stage has a green

mode function. Frequency linearly decreases when V_FB

is within V_Gand V_N. Once V_FBis lower than V_G,

switching frequency disables, and it enters burst mode.

Figure 25. Remote On/Off

FAN6791 / FAN6793 • Rev. 1.0.2

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13

Interleave Switching

Constant Power Control

The FAN6791/3 uses interleaved switching to

synchronize the stand-by PWM / forward PWM stages.

This reduces switching noise and spreads the EMI

emissions. Figure 26 shows that an off-time t_OFFis

inserted in between the turn-off of the stand-by gate

drives and the turn-on of the forward PWM.

To limit the output power of the converter constantly, a

power-limit function is included. Sensing the converter

input voltage through the VRMS pin, the power limit

function generates a relative peak-current-limit threshold

voltage for constant power control, as shown in Figure 28.

Figure 26. Interleaved Switching

Slope Compensation

The stand-by PWM and forward PWM stage are

designed for flyback and forward power converters.

Peak-current-mode control is used to optimize system

performance. Slope compensation is added to stabilize

Figure 28. Constant Power Control

Protections

the current loop. The FAN6791/3 inserts

a

synchronized, positively sloped ramp at each switching

cycle. The positively sloped ramp is represented by the

voltage signal V_s-compin Figure 27.

The FAN6791/3 provides full protection functions to

prevent the power supply and the load from being

damaged. The protection features include:

V_DDOver-Voltage Protection. The stand-by PWM and

forward PWM stages will be disabled whenever the

VDD voltage exceeds the over-voltage threshold.

AC Under-Voltage Protection. The VRMS pin is used to

detect the AC input voltage. When voltage is lower than

the brownout threshold, voltage disables both forward

and stand-by PWM.

RI Pin Open / Short Protection. The RI pin is used to set

the switching frequency and internal current reference.

The stand-by PWM and forward PWM stages are

disabled whenever the RI pin is short or open.

Open-Loop Protection. The stand-by PWM and forward

PWM stages of FAN6791/3 is disabled whenever the

FBFYB / FBPWM pin is open.

Figure 27. Slope Compensation

Gate Drivers

FAN6791/3 output stages are fast totem-pole gate

drivers. The output driver is clamped by an internal 18V

Zener diode to protect the power MOSFET.

FAN6791 / FAN6793 • Rev. 1.0.2

www.fairchildsemi.com

14

Reference Circuit

Figure 29. Reference Circuit

FAN6791 / FAN6793 • Rev. 1.0.2

www.fairchildsemi.com

15

BOM List

Reference

Component

C/0.47µF/X2

C/471P/50V

C/102P/50V

C/472/400V

C/102P/50V

C/10µF/50V

C/104P/50V

C/102P/1KV

C/470µF/200V

C/103P/1KV

C/1000µF/10V

C/330µF/10V

C/103P/50V

R/680K 1/4W NC

R/680K 1/4W

R/51.1K 1/4W

R/2.4M 1/4W

R/24K 1/8W

R/1K 1/8W

Reference

R18

R20

R21

R22

R23

R24

R26

R29

R31

R35

R37

R38

Q1

Component

R/100 1/8W

R/1/1W

C1

C2

C3

R/1 1/8W

R/402 1/8W

R/47K 3W

R/10K 1/8W

R/2K 1/8W

R/470 1/8W

R/0.1/2W

R/N.A 1/4W

R/20K 1% 1/8W

2N/60

C4

C5

C6

C7

C8

C9

C10

C11

C12

C20

C21

C22

C23

C24

C25

C28

R1

Q2

9N90

Z3

7D271

Z2

7D271

Z1

7D561

D1

D/1N4007

D/UF107

D/SB540

D/UF1007

D/6A/600V

SG6791/3

PC-817

D2

D3

R2

D4

R3

BD1

U1

R4

R5

U2

R6

U3

TL431

R7

U6

PC-817

R8

R9

R/19.1K 1/8W

R/1K 1/8W

R10

R13

R14

R15

R17

R/100K 1/2W

R/10 1/8W

R/100 1/8W

FAN6791 / FAN6793 • Rev. 1.0.2

www.fairchildsemi.com

16

Physical Dimension

A

19.68

18.66

9

16

6.60

6.09

1

8

(0.40)

TOP VIEW

0.38 MIN

5.33 MAX

8.13

7.62

3.42

3.17

3.81

2.92

15

0

0.35

0.20

2.54

0.58

0.35

A

1.78

1.14

8.69

17.78

SIDE VIEW

NOTES: UNLESS OTHERWISE SPECIFIED

A

THIS PACKAGE CONFORMS TO

JEDEC MS-001 VARIATION BB

B) ALL DIMENSIONS ARE IN MILLIMETERS.

C) DIMENSIONS ARE EXCLUSIVE OF BURRS,

MOLD FLASH, AND TIE BAR PROTRUSIONS

D) CONFORMS TO ASME Y14.5M-1994

E) DRAWING FILE NAME: N16EREV1

Figure 30. 16-pin Dual In-Line Package (DIP)

Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner

without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor 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 visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:

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

FAN6791 / FAN6793 • Rev. 1.0.2

www.fairchildsemi.com

17

Physical Dimensions (Continued)

Figure 31. 16-Pin Small Outline Package (SOIC)

Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner

without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor 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 visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:

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

FAN6791 / FAN6793 • Rev. 1.0.2

www.fairchildsemi.com

18

FAN6791 / FAN6793 • Rev. 1.0.2

www.fairchildsemi.com

19


型号：	FAN6791
厂家：	FAIRCHILD SEMICONDUCTOR
描述：	Highly Integrated, Dual-PWM Combination Controller 高度集成的双PWM组合控制器控制器
文件：	总19页 (文件大小：718K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

FAN6791 [FAIRCHILD]

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