AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
™
ChargePump
General Description
Features
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 AS2Cwire™ (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.
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VIN Range: 2.7V to 5.5V
Dual Charge Pump to Support Backlight and
Flash LEDs
Backlight Charge Pump:
— Regulated Current
— Four Current Sink Inputs
— AS2Cwire Brightness Control
— Tri-Mode Charge Pump
— Maximum 30mA of Current Per Input
— Low IQ (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
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Automatic Soft-Start
No Inductors
Available in TDFN44-16 Package
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.
Applications
The AAT2805 has thermal protection and built-in
soft-start circuitry. A low-current shutdown feature
disconnects the load from VIN and reduces quiescent
current to less than 1µA.
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Color (RGB) Lighting
White LED Backlighting
White LED Photo Flash
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.
Typical Application
C1
1µF
C2
1µF
C3
1µF
C1+ C1- C2+ C2- C3+ C3-
VOUT_FL
VOUT_FLASH
COUT
1µF
Flash
VIN
AAT2805
V
CIN
1µF
IN
Backlight
D4
VOUT_BL
D2
D3
D1
EN/SET
EN/SET
D1
D2
D3
EN_FLSH
EN_FLSH
COUT
1µF
D4
GND
2805.2005.05.1.2
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