AAT1235
High Efficiency White LED Drivers
for Backlight and Keypad
™
SwitchReg
General Description
Features
The AAT1235 is a highly integrated, high efficiency
power solution for white LED backlight and keypad
backlights in mobile/portable devices. It is based on a
switching boost converter which steps up the single-
cell lithium-ion/polymer battery voltage to drive 5
strings of series-connected white LEDs with preci-
sion current regulation. The AAT1235 is capable of
driving a total of four LEDs per channel.
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Input Supply Voltage Range: 2.7V to 5.5V
Maximum Boost Output Drive: Up to 24V at 100mA
Up to 85% Efficient Operation
Up to 2MHz Switching Frequency with Small
Inductor
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User-Programmable Full-Scale LED Current, Up
to 30mA
Single-Wire AS2Cwire Serial Interface
— Five Addressable Registers
The boost converter can produce an output drive of
up to 24V at 100mA. The high switching frequency
(up to 2MHz) provides fast response to load tran-
sients and allows the use of small external compo-
nents. A fully integrated control circuit simplifies the
design and reduces total solution size.
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Independent LED Current Control by Group
— Backlight Group B1-B2, 16 Settings
— Auxiliary Group A1-A3, 16 Settings
Independent LED ON/OFF Control
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— Fast, 1MHz Serial Interface
Non-Pulsating, High-Performance LED Current
Drive for Uniform Illumination
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AnalogicTech's Advanced Simple Serial Control™
(AS2Cwire™) serial digital input is used to individual-
ly turn each output sink on/off and adjust the LED
current by group. Unlike conventional pulse width
modulation (PWM) control of LED brightness, the
AAT1235 drives the LEDs with constant, non-pulsat-
ing current.
— 10% Absolute Accuracy
— 2% Channel-to-Channel Matching
Over-Voltage and Over-Temperature Protection
Automatic Soft-Start Minimizes Large Inrush
Current at Startup
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Available in 3x4mm TDFN34-16 Package
A similar device is also available with an I2C two-
wire interface; please see the AAT1236 datasheet.
Applications
The AAT1235 is available in a Pb-free, thermally-
enhanced 16-pin 3x4mm TDFN package and is
specified for operation over the -40°C to +85°C tem-
perature range.
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Digital Still Cameras (DSCs)
Keypad Backlight
Large Panel Displays
Mobile Handsets
Personal Media Players
PDAs and Notebook PCs
White LED Backlight
Typical Application
Keypad or
RGB LEDs
L= 2.2µH
D1
Up to 24V Max
COUT
2.2µF
Backlight
LEDs
R2
187kΩ
LIN
B1 B2
A1 A2 A3
OV
SW
Input :
2.7V~5.5V
VIN
IN
AAT1235
R3
CIN
12.1kΩ
2.2µF
EN/SET
AGND
RSET GND
R1
22.6kΩ
AS2Cwire Control
1235.2007.02.1.1
1