AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
2805.2005.05.1.2 1
ChargePump
™
General Description
The AAT2805 is a dual charge pump designed to
support both the white LED backlight and flash appli-
cations for systems operating with lithium-ion/poly-
mer batteries. The backlight charge pump is capable
of driving up to four LEDs at a total of 120mA. The
current sinks may be operated individually or in par-
allel 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 selected 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, dis-
able, and set current for each LED with a 16-level
logarithmic scale plus four low-current settings down
to 50µA for optimized efficiency, with a typical oper-
ating quiescent current of less than 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
250mA of pulsed current. It has an independent
enable pin for improved power savings.
The AAT2805 has thermal protection and built-in
soft-start circuitry. A low-current shutdown feature
disconnects the load from V
IN
and reduces quiescent
current to less than 1µA.
The AAT2805 is available in a space-saving, ther-
mally-enhanced TDFN44-16 package and is rated
over the -40°C to +85°C temperature range.
Features
•V
IN
Range: 2.7V to 5.5V
• Dual Charge Pump to Support Backlight and
Flash LEDs
• Backlight Charge Pump:
— Regulated Current
— Four Current Sink Inputs
—AS
2
Cwire Brightness Control
— Tri-Mode Charge Pump
— Maximum 30mA of Current Per Input
— Low I
Q
(50µA) in Light Load Mode
• Flash Charge Pump:
— Regulated Output Voltage
— Up to 250mA of Pulsed Current
• Independent Backlight/Flash Control
• Low Noise 1MHz Constant Frequency
Operation
• Automatic Soft-Start
• No Inductors
• Available in TDFN44-16 Package
Applications
• Color (RGB) Lighting
• White LED Backlighting
• White LED Photo Flash
Typical Application
AAT2805
C
IN
1µF
V
IN
C
OUT
1µF
EN/SET
C1
1µF
D3D2D1
VIN
C1+ C1- C2+ C2- C3+ C3-
D2
GND
Backlight
C2
1µF
C3
1µF
Flash
VOUT_FL
VOUT_BL
C
OUT
1µF
EN_FLSH
EN/SET
EN_FLSH
D1
D3
D4
V
OUT_FLASH
D4