Fairchild RD-268 Schematics

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Reference Design RD-268

PFC+PWM Combination Controller FAN4800A, Fairchild Power Switch,
FPS™ FSBH0370 and Supervisor IC SG 6520 - 300W Design (80 Plus)

Featured Device Application

FAN4800A
FSBH0370

SG6520

ATX PC Power 85~265V

Input Voltage

Range

AC

Output Voltage

(Rated Current)

12V1 (6A)

12V2 (10.5A)

5V (9A)

3.3V (13.5A)

-12V (0.3A)
5V

SB

(2A)

Key Features

FAN4800A

 Pin-to-Pin Compatible with ML4800, FAN4800 , CM6800, and CM6800A
 PWM Configurable for Current-Mode or Feedforward Voltage-Mode Operation
 Internally Synchronized Leading-Edge PFC and Trailing-Edge PWM in One IC
 Low Opera ting Current
 Innovative Switching-Charge Multiplier Divider
 Average-Current Mode for Input-Current Shaping
 PFC Over-Voltage, Under-Voltage, and Feedback Open-Loop Protection
 Cycle-by-Cycle Current Limiting for PWM
 Power-On Sequence Control and Soft-Start
 Brownout Protection

Rated Output

Power

300W

Topology

CCM Boost PFC

+ Two Switch

Forward +

Flyback

FSBH0370

 Internal Avalanche-Rugged SenseFET (700V) in TO220 Package
 Constant Power Limit
 Advanced Burst-Mode Operation and Green-Mode Function for Low Standby Power Consumption
 Internal High Voltage Startup Circuit
 Various Protection Functions: Over-Voltage Protection (OVP), Overload Protection (OLP), Internal

Thermal Shut down Functi on (TSD), Brownout Protection

 Built-in Slope Compensation
 Built-in Soft-Start: 5ms

SG6520

 Two 12V Sense Input Pins: VS12 and VS12B
 Over-Voltage Protection (OVP), Over-Current Protection (OCP), and Under-Voltage Protection (UVP) for

3.3V, 5V, and Two 12V

 Open-Drain Output for PGO and FPO Pins
 300ms Power Good Delay
 300ms Turn-on Delay for 3.3V, 5V, and Two 12V
 2.8ms PSON Control to FPO Turn-off Delay and 48ms PSON Control Delay
 No Lockup During the Fast AC Power On/Off
 Wide Supply Voltage Range: 4.2V to 15V
 Programmable Over-Temperature Protection (OTP)

© 2009 Fairchild Semiconductor Corporation 1 RD-268_FAN4800A • Rev. 0.0.1

www.fairchildsemi.com

1. Schematics

Figure 1. Schematic of Auxiliary Power (FSBH0X70) and Supervisory IC (SG6515/20)

© 2009 Fairchild Semiconductor Corporation 2 RD-268_FAN4800A • Rev. 0.0.1

www.fairchildsemi.com

Figure 2. Schematic of Main Power Stage (FAN4800A)

© 2009 Fairchild Semiconductor Corporation 3 RD-268_FAN4800A • Rev. 0.0.1