AP3503 datasheet(2/11 Pages) BCDSEMI

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Data Sheet

340kHz, 3A Synchronous DC-DC Buck Converter

AP3503

May. 2012

Rev. 1. 7

BCD Semiconductor Manufacturing Limited

Pin Configuration

MP Package

(PSOP-8)

Figure 2. Pin Configuration of AP3503 (Top View)

Pin Description

Pin Number

Pin Name

Function

Bootstrap pin. A bootstrap capacitor is connected between the BS pin

and SW pin. The voltage across the bootstrap capacitor drives the

internal high-side power MOSFET

Supply power input pin. A capacitor should be connected between the

IN pin and GND pin to keep the input voltage constant

Power switch output pin. This pin is connected to the inductor and

bootstrap capacitor

GND

Ground pin

Feedback pin. This pin is connected to an external resistor divider to

program the system output voltage. When the FB pin voltage exceeds

1.1V, the over voltage protection is triggered. When the FB pin

voltage is below 0.3V, the oscillator frequency is lowered to realize

short circuit protection

COMP

Compensation pin. This pin is the output of the transconductance

error amplifier and the input to the current comparator. It is used to

compensate the control loop. Connect a series RC network from this

pin to GND. In some cases, an additional capacitor from this pin to

GND pin is required

Control input pin. EN is a digital input that turns the regulator on or

off. Drive EN high/low to turn on/off the regulator. Pull up with

100k

Ω resistor for automatic startup

Soft-start control input pin. SS controls the soft-start period. Connect

a capacitor from SS to GND to set the soft-start period. A 0.1

µF

capacitor sets the soft-start period to 15ms. To disable the soft-start

feature, leave SS unconnected

Exposed pad. It should be connected to GND in PCB layout

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