Dual High Efficiency Charge Pump
for White LED and Flash Applications
General Description
The AAT2806 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 80mA. The cur-
rent sinks may be operated individually 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 automati-
cally selected by comparing the forward voltage of
each LED with the input voltage. AnalogicTech's
S
2
Cwire™ (Simple Serial Control™) serial digital
input is used to enable, disable, and set current for
each LED with an eight-level logarithmic scale plus
four low-current settings down to 50µA for optimized
efficiency, with a typical operating 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 AAT2806 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 AAT2806 is available in a Pb-free, space-saving,
thermally-enhanced TDFN44-16 package and is
rated over the -40°C to +85°C temperature range.
AAT2806
Features
•
•
•
ChargePump
™
•
•
•
•
•
•
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
— S
2
Cwire Brightness Control
— Tri-Mode Charge Pump
— Maximum 20mA 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
C1
1μF
C2
1μF
C3
1μF
C1+ C1- C2+ C2- C3+ C3-
VOUT_FL
VIN
V
IN
C
IN
1μF
C
OUT
1μF
V
OUT_FLASH
Flash
AAT2806
VOUT_BL
Backlight
D1
EN/SET
EN_FLSH
EN/SET
EN_FLSH
GND
D1
D2
D3
D4
D2
D3
D4
C
OUT
1μF
2806.2006.04.1.8
1
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
