AP3720 datasheet(2/13 Pages) BCDSEMI

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Preliminary Datasheet

CURRENT MODE PWM CONTROLLER FOR BJT

AP3720

Jul. 2009 Rev. 1. 0

BCD Semiconductor Manufacturing Limited

Pin Configuration

P Package

M Package

(DIP-8)

(SOIC-8)

LINE

BIAS

GND

DRV

VCC

LINE

BIAS

GND

DRV

VCC

Figure 2. Pin Configuration of AP3720 (Top View)

Pin Description

Pin Number

Pin Name

Function

LINE

Line compensation for OLP

No connection

Connect opto-coupler to this pin. The voltage of FB controls the mode

of operation in one of the three modes: burst mode, frequency-drop

mode (20kHz) and normal mode (65kHz). When the voltage of FB

reaches a limit-point, the system enters the OLP mode

BIAS

This pin sets the driver current inside AP3720 with an external resistor

to GND

VCC

This pin is the positive supply voltage input. During start up, the

power is supplied from line voltage. When VCC reaches 20V, the

system begins running and the power is supplied from the auxiliary

transformer winding

DRV

This pin supplies the drive current for the external power NPN switch

GND

This pin is the control ground

This pin senses the primary current and routes it to internal

comparator. By changing the value of the sense resistor, the primary

peak current set point is adjusted according to the output power

demand

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