Preliminary Datasheet

380kHz, 3A Asynchronous DC - DC Buck Converter

AP3203

Mar. 2011 Rev. 1. 0

BCD Semiconductor Manufacturing Limited

2

Pin Configuration

MP Package

(PSOP-8)

Figure 2. Pin Configuration of AP3203 (Top View)

Pin Description

Pin Number

Pin Name

Function

1

BS

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 NMOS switch

2

IN

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

and GND pin to keep the DC input voltage constant

3

SW

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

bootstrap capacitor

4

GND

Ground pin

5

FB

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

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

20% of the nominal regulation value of 1.222V, the over voltage

protection is triggered. When the FB pin voltage is below 0.6V, the

oscillator frequency is lowered to realize short circuit protection

6

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

7

EN

Control input pin. Forcing this pin above 1.5V or set this pin floating

enables the IC. Forcing this pin below 0.5V shuts down the IC. When

the IC is in shutdown mode, all functions are disabled to decrease the

supply current below 1

µA

8

SS

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

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

capacitor sets the soft-start period to 10ms. To disable the soft-start

feature, leave SS disconnected