AP1521

White LED Step-Up 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. 0.1 Apr. 27, 2004

1/8

Features

- Inherently Matched LED Current

- Drives Up to Four LEDs from a 3.2V Supply

- Drives Up to Six LEDs from a 5V Supply

- High Efficiency: 84% Typical

- Fast 1MHz Switching Frequency

- 36V Rugged Bipolar Switch

- Low Profile SOT23-5 Pb-Free Packaging

Applications

- Cellular Phones

- PDAs, Hand-held Computers

- Digital Cameras

- MP3 Players

- GPS Receivers

General Description

The AP1521 is a step-up DC/DC converter

specifically designed to drive white LEDs with a

constant current. The device can drive two, three or

four LEDs in series from a Li-Ion cell. Series

connection of the LEDs provides identical LED

currents resulting in uniform brightness and

eliminates the need for ballast resistors. The

AP1521 switches at 1MHz that allows the use of

tiny external components. A low 300mV feedback

voltage minimizes power loss in the current setting

resistor for better efficiency.

Pin Assignments

V

IN

SHDN

SW V

SS

FB

Top View

SOT23-5L

Pin Descriptions

Name

Description

SW

Switch Pin. Connect inductor/diode

here. Minimize trace area at this pin

to reduce EMI.

GND pin

FB

Feedback Pin. Reference voltage is

310mV. Connect cathode of lowest

LED and resistor here. Calculate

resistor value according to the

SHDN

Shutdown Pin. Tie to 1.5V or higher

to enable the device；0.4V or less to

disable the device.

Input Supply Pin. Must be locally

bypassed.

Ordering Information

Package

W: SOT23-5L

AP1521 X X

Packing

Blank : Tube

A

: Taping