Dual LED Flash Driver with
I2C-Compatible Interface
ADP1655
FEATURES
FUNCTIONAL BLOCK DIAGRAM
INPUT VOLTAGE = 2.5V TO 5.5V
Ultracompact solution
10µF
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
I2C programmable
2.2µH
STROBE VIN
TORCH
SW
VOUT
10µF
ADP1655
SCL/EN1
SDA/EN2
LED_OUT
TX_MASK
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
I2C/EN SGND PGND
Figure 1.
Flash timer
Control
I2C-compatible control registers
External STROBE pin
Li-ION +
C1
L1
Li-ION +
PGND
External direct TORCH pin
TX_MASK input to prevent high input battery current levels
Safety
3mm
INDUCTOR
Thermal overload protection
Flash timeout
DIGITAL
C2
INPUT/
OUTPUT
Inductor fault detection
Output overvoltage
LED
ANODE
Short circuit protection
6.5mm
Soft start reduces inrush input current
Figure 2. PCB Layout
APPLICATIONS
Camera-enabled cellular phones and smart phones
Digital still cameras, camcorders, and PDAs
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
convertor, an I2C-compatible interface and a 500 mA current
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.
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.
The I2C-compatible interface enables the programmability
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.
The efficiency is high over the entire battery voltage range to
maximize the input power to LED power conversion and
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
www.analog.com
©2009 Analog Devices, Inc. All rights reserved.
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