Dual LED Flash Driver with

ADP1655

Rev. 0

Information furnished by Analog Devices is believed to be accurate and reliable. However, no

responsibilityis assumedbyAnalogDevicesforitsuse,norforanyinfringementsof patentsorother

rightsofthirdpartiesthatmayresultfromitsuse.Specificationssubjecttochangewithoutnotice.No

license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781.329.4700

www.analog.com

Fax: 781.461.3113

©2009 Analog Devices, Inc. All rights reserved.

FEATURES

Ultracompact solution

Small 2 mm × 1.5 mm 12-ball WLCSP package

Tiny, low profile 2.2 μH power inductor

LED current source for local LED grounding and low EMI

Synchronous 2 MHz PWM boost convertor, no external diode

High efficiency: 88% peak

Reduces high levels of input battery current during flash

Limits battery current drain in torch mode

Currents up to 400 mA in flash mode for two LEDs

Currents up to 500 mA in flash mode for one LED with

5% accuracy

Currents up to 160 mA in torch mode with 10% accuracy

Peak inductor current limit

Flash timer

Control

External STROBE pin

External direct TORCH pin

TX_MASK input to prevent high input battery current levels

Safety

Thermal overload protection

Flash timeout

Inductor fault detection

Output overvoltage

Short circuit protection

Soft start reduces inrush input current

APPLICATIONS

Camera-enabled cellular phones and smart phones

Digital still cameras, camcorders, and PDAs

FUNCTIONAL BLOCK DIAGRAM

ADP1655

10µF

2.2µH

INPUT VOLTAGE = 2.5V TO 5.5V

TORCH

SCL/EN1

I2C/EN SGND PGND

SDA/EN2

VOUT

LED_OUT

TX_MASK

STROBE VIN

SW

10µF

Figure 1.

L1

INDUCTOR

DIGITAL

INPUT/

OUTPUT

LED

ANODE

Li-ION +

Li-ION +

PGND

C1

3mm

6.5mm

C2

Figure 2. PCB Layout

GENERAL DESCRIPTION

The ADP1655 is a very compact, highly efficient, dual white

LED flash driver for high resolution camera phones, which

improves picture and video quality in low light environments.

The device integrates a 2 MHz synchronous inductive boost

source. The high switching frequency enables the use of a tiny,

low profile 2.2 μH power inductor, and the current source

permits LED cathode grounding for thermally enhanced,

low EMI and compact layouts.

The efficiency is high over the entire battery voltage range to

maximize the input power to LED power conversion and

minimize battery current draw during flash events. In addition,

a Tx-mask input permits the flash LED current to reduce quickly

and, therefore, the battery current reduces quickly, during a

GSM power amplifier current burst.

of timers, currents, and status bit readback for operation

monitoring and safety control.

The ADP1655 comes in a compact 12-ball 0.5 mm pitch

WLCSP package and is specified over the full −40°C to

+125°C junction temperature range.