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FAN4803
8-Pin PFC and PWM Controller Combo

Features
Internally synchronized PFC and PWM in one 8-pin IC Patented one-pin voltage error amplifier with advanced input current shaping technique Peak or average current, continuous boost, leading edge PFC (Input Current Shaping Technology) High efficiency trailing-edge current mode PWM Low supply currents; start-up: 150 A typ., operating: 2mA typ. Synchronized leading and trailing edge modulation Reduces ripple current in the storage capacitor between the PFC and PWM sections Overvoltage, UVLO, and brownout protection PFC VCCOVP with PFC Soft Start

General Description
The FAN4803 is a space-saving controller for power factor corrected, switched mode power supplies that offers very low start-up and operating currents. Power Factor Correction (PFC) offers the use of smaller, lower cost bulk capacitors, reduces power line loading and stress on the switching FETs, and results in a power supply fully compliant to IEC1000-3-2 specifications. The FAN4803 includes circuits for the implementation of a leading edge, average current "boost" type PFC and a trailing edge, PWM. The FAN4803-1 s PFC and PWM operate at the same frequency, 67kHz. The PFC frequency of the FAN4803-2 is automatically set at half that of the 134kHz PWM. This higher frequency allows the user to design with smaller PWM components while maintaining the optimum operating frequency for the PFC. An overvoltage comparator shuts down the PFC section in the event of a sudden decrease in load. The PFC section also includes peak current limiting for enhanced system reliability.

Block Diagram
7 VEAO 4 35 A
1

7V

PFC OFF

VCC
17.5V 16.2V

REF VCC OVP
COMP

VREF GND 2

COMP

M3 M4 PFC CONTROL LOGIC PFC OUT 1

M1

M2 R1 M7 C1 30pF

LEADING EDGE PFC ONE PIN ERROR AMPLIFIER 3 ISENSE
4

PFC ILIMIT
VCC

COMP

SOFT START

TRAILING EDGE PWM

1V

PFC/PWM UVLO OSCILLATOR PFC 67kHz PWM 134kHz

VREF VDC 26k

DUTY CYCLE LIMIT

5

PWM COMPARATOR PWM CONTROL LOGIC

40k 1.2V 6 ILIMIT

COMP

COMP

PWM OUT 8

M6 1.5V

DC ILIMIT

REV. 1.2.3 11/2/04

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FAN4803-2 DATASHEET