AP5724

WHITE LED STEP-UP CONVERTER

AP5724

Document number: DS31843 Rev. 3 - 2

1 of 17

www.diodes.com

July 2010

© Diodes Incorporated

Description

The AP5724 is a step-up DC/DC converter specifically

designed to drive white LEDs with a constant current. The

device can drive 2 ~ 6 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. For driving higher number of LEDs,

AP5724

also

supports

a

single

feedback

of

parallel

connected multiple strings of equal number of LEDs.

The AP5724 switches at 1.2MHz that allows the use of tiny

external components. A low 0.1V feedback voltage minimizes

power loss in the current setting resistor for better efficiency.

Pin Assignments

1

2

3

74

6

OVP

FB

5

EN

SW

(Top View)

GND

SOT26 / TSOT23-6

SW

OVP

1

2

3

6

5

4

GND

FB

EN

(Top View)

DFN2020C-6

Features

•

High efficiency: 84% typical

•

Fast 1.2MHz switching frequency

•

Current limit and UVLO protections

•

Internal thermal shutdown

•

Internal Over Voltage Protection

•

Integrated soft-start function

•

SOT26, TSOT23-6 and DFN2020C-6: Available in

“Green” Molding Compound (No Br, Sb)

•

Lead Free Finish/ RoHS Compliant (Note 1)

Applications

•

Cellular Phones

•

PDAs, Hand held Computers

•

Digital Cameras

•

MP3 Players

•

GPS Receivers

Notes:

1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at

http://www.diodes.com/products/lead_free.html.

Typical Application Circuit

V

IN

SW

EN

GND

FB

AP5724

C

OUT

1uF

5

L1

22uH

D1

V

IN

1uF

OVP

2~6 LEDs

PWM Dimming

OFF

ON

Figure 1. Typical Application Circuit