AAT1235 Datasheet, PDF (1/21 Pages) Advanced Analogic Technologies – High Efficiency White LED Drivers for Backlight and Keypad

General Description
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.
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.
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.
A similar device is also available with an I²C two-
wire interface; please see the AAT1236 datasheet.
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.
Typical Application
L= 2.2µH
D1
COUT
2.2µF
AAT1235
High Efficiency White LED Drivers
for Backlight and Keypad
Features
SwitchReg^™
• 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
• User-Programmable Full-Scale LED Current, Up
to 30mA
• Single-Wire AS²Cwire Serial Interface
— Five Addressable Registers
• Independent LED Current Control by Group
— Backlight Group B1-B2, 16 Settings
— Auxiliary Group A1-A3, 16 Settings
• Independent LED ON/OFF Control
— Fast, 1MHz Serial Interface
• Non-Pulsating, High-Performance LED Current
Drive for Uniform Illumination
— 10% Absolute Accuracy
— 2% Channel-to-Channel Matching
• Over-Voltage and Over-Temperature Protection
• Automatic Soft-Start Minimizes Large Inrush
Current at Startup
• Available in 3x4mm TDFN34-16 Package
Applications
• Digital Still Cameras (DSCs)
• Keypad Backlight
• Large Panel Displays
• Mobile Handsets
• Personal Media Players
• PDAs and Notebook PCs
• White LED Backlight
Up to 24V Max
Keypad or
RGB LEDs
LIN
Input :
2.7V~5.5V
VIN
CIN
2.2µF
IN
AS ²Cwire Control
Backlight
LEDs
SW
B1 B2 A1 A2 A3
AAT1235
OV
EN /SET
RSET
R1
22.6kΩ
GND AGND
R2
187kΩ
R3
12.1kΩ
1235.2007.02.1.1
1