AL3157

HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER

FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT

AL3157

Document number: DS35116 Rev. 1 - 2

1 of 9

www.diodes.com

March 2011

© Diodes Incorporated

Description

The AL3157 is a low noise, constant frequency charge

pump DC/DC converter that uses a Dual mode load switch

(1x), and doubling (2x) conversion for driving white LEDs.

Low external part count (one 1µF flying capacitor and two

suited for small, battery-powered applications

The AL3157 drives 3 channels at up to 30mA for small

screen backlighting and an additional channel up to 210mA

for LED Flash or LED Flashlight – All from a 2.7V to 5.5V

input.

The

AL3157

uses

two

control

inputs

(EN1/2)

to

enable/disable it and PWM dim the LED current. EN2

controls/PWM dims the backlight LEDs at 30mA per

channel and EN1 controls/PWM dims the Flash/Flashlight

LEDs at 210mA.

short circuit and auto-disable for LED failure conditions.

Built-in soft-start circuitry prevents excessive in-rush

current during start-up and mode switching. A low-current

quiescent current less than 1µA.

The AL3157 is available in a lead-free, space-saving

thermally enhanced 12-pin 3x3mm DFN package.

Pin Assignments

D4

D1

D2

EN1

7

6

5

4

3

2

1

10

11

12

9

8

PGND

EN2

Exposed Pad

( Top View )

D3

GND

U-DFN3030-12

Features

•

Dual-Mode 1x and 2x Charge Pump

•

Up to 300mA drive capability

o

3-channel for backlight – 30mA/ch

o

1-channel for Flight/light – 210mA

•

•

Two simple PWM dimming control inputs up to

50kHz

•

1.2 MHz Constant Switching Frequency

•

Protection

•

Soft Start for reducing in-rush current

•

•

Thermally-Enhanced DFN3030-12 Package:

Available in “Green” Molding Compound (No Br, Sb)

•

Lead Free Finish/ RoHS Compliant (Note 1)

Applications

•

Smart Touch Phone LED Backlighting

•

PDA White LED backlighting

•

Backlighting + Torch light

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

AL3157

V

OUT

D1

D2

D3

D4

EN2

EN1

EN2

EN1

2.2µF

C

IN

V

IN

V

IN

1µF

C

1

C

P

C

N

5

3

6

12

10

8

7

1

11

4

PGND

GND

29

2.2µF

C

OUT

Flash/

Light

(EN1)

Backlight

(EN2)

AL3157

V

OUT

D1

D2

D3

D4

EN2

EN1

EN2

EN1

2.2µF

C

IN

V

IN

V

IN

1µF

C

1

C

P

C

N

5

3

6

12

10

8

7

1

11

4

PGND

GND

29

2.2µF

C

OUT

Flash/

Light

(EN1)

Backlight

(EN2)