AP1537

PWM Control 3A Step-Down Converter

This datasheet contains new product information. Anachip Corp. reserves the rights to modify the product specification without notice. No liability is assumed as a result of the use of

this product. No rights under any patent accompany the sale of the product.

Rev. 1. 3

May 09, 2006

1/7

Features

- Input voltage: 3.6V to 18V.

- Duty ratio: 0% to 100% PWM control

- Oscillation frequency: 500KHz typ.

- Soft-start, Current Limit, Enable function

- Thermal Shutdown function

- Built-in internal SW P-channel MOS

- Low ESR output capacitor (Multi-layer chip

capacitor (MLCC)) application

- SOP-8L Pb-Free Package.

Applications

- PC Motherboard

- LCD Monitor

- Graphic Card

- DVD-Video Player

- Telecom Equipment

- ADSL Modem

- Printer and other Peripheral Equipment

- Microprocessor core supply

- Networking power supply

General Description

AP1537 consists of step-down switching regulator

with PWM control. These devices include a reference

voltage source, oscillation circuit, error amplifier,

internal PMOS and etc.

AP1537 provides low-ripple power, high efficiency,

and excellent transient characteristics. The PWM

control circuit is able to vary the duty ratio linearly

from 0 up to 100%. This converter also contains an

error amplifier circuit as well as a soft-start circuit that

prevents overshoot at startup. An enable function,

an over current protect function and a short circuit

protect function are built inside, and when OCP or

SCP happens, the operation frequency will be

reduced from 500KHz to 50KHz. Also, an internal

compensation block is built in to minimum external

component count.

With the addition of an internal P-channel Power MOS,

a coil, capacitors, and a diode connected externally,

these ICs can function as step-down switching

regulators. They serve as ideal power supply units for

portable devices when coupled with the SOP–8L

mini-package, providing such outstanding features as

low current consumption. Since this converter can

accommodate an input voltage up to 18V, it is also

suitable for the operation via an AC adapter.

Pin Assignments

)

1

2

3

4

8

7

6

5

FB

Output

Comp

AP1537

Output

EN

Vss

Vss

Pin Descriptions

Name

Pin

Description

FB

1

Feedback pin

EN

2

Power-off pin

H: Normal operation

(Step-down operation)

L: Step-down operation stopped

(All circuits deactivated)

Comp

3

Compensation pin

4

IC power supply pin

Output

5、6

Switch

Pin.

Connect

external

inductor/diode here. Minimize trace

area at this pin to reduce EMI.

7、8 GND Pin