Six-Channel White LED Backlight
Charge Pump with Flash
General Description
The AAT2803 is a dual charge pump designed to sup-
port both white LED backlight and flash applications
for systems operating with lithium-ion/polymer batter-
ies. The backlight charge pump is capable of driving
up to six LEDs at a total of 180mA. The current sinks
may be operated in group or in parallel for driving
higher current LEDs. To maximize power efficiency,
the charge pump operates in 1X, 1.5X, or 2X mode,
where the mode of operation is automatically select-
ed by comparing the forward voltage of each LED
with the input voltage. AnalogicTech's AS
2
Cwire™
(Advanced Simple Serial Control™) serial digital input
is used to enable, disable, and set current for each
LED with a 16-level logarithmic scale plus four low-
current settings down to 50μA for optimized efficien-
cy, with a low housekeeping current of only 50μA.
The flash charge pump is a charge pump doubler
with a regulated output voltage. It is designed to
deliver 120mA of continuous current and up to
300mA of pulsed current. It has an independent
enable pin for improved power savings.
The AAT2803 is equipped with built-in protection,
short-circuit, and auto-disable for load short-circuit
condition. Built-in soft-start circuitry prevents exces-
sive inrush current during start-up. A low-current
shutdown feature disconnects the load from V
IN
and
reduces quiescent current to less than 1μA.
The AAT2803 is available in a Pb-free, space-saving,
thermally enhanced 24-pin 4x4mm QFN package
and is rated over the -40°C to +85°C temperature
range.
AAT2803
Features
•
•
•
ChargePump
™
•
•
•
•
•
•
•
•
V
IN
Range: 2.7V to 5.5V
Dual Charge Pump:
— Flash: Charge Pump Doubler
— Backlight: Tri-Mode Charge Pump
Backlight Charge Pump:
— Programmable Current With Single GPIO
— 16 Current Steps
— 15/20/30mA Max Current
— Four Low Current Settings
— Individual Main/Sub-Group Control
— Low I
Q
(50μA) for Low-Current Mode
— Drives Six Channels of LEDs
Flash Charge Pump:
— Regulated V
OUT_FL
4.5/5.0 Volts
— Up to 300mA of Current for Flash
1MHz Constant Switching Frequency
Independent Backlight/Flash Control
Built-In Thermal Protection
Built-In Auto-Disable for Open Circuit
Automatic Soft Start
I
Q
<1μA in Shutdown
Available in QFN44-24 Package
Applications
•
•
•
•
Color (RGB) Lighting
Programmable Current Sink
White LED Backlighting
White Photo Flash for Digital Still Cameras
Typical Application
C1
1μF
C2
1μF
C3
1μF
C1
+
VIN
V
IN
C
IN
1μF
C1
-
C2
+
C2
-
C3
+
C3
-
VOUT
C
OUT
1μF
Flash
AAT2803
D6
D5
D4
D3
D2
Backlight
D1
EN_FL
ENFL
C
OUT
1μF
EN/SET
EN/SET
GND
D6
D5
D4
D3
D2
D1
2803.2006.04.1.5
1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
