High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
General Description
The AAT3140 is a low noise, constant frequency
charge pump DC/DC converter that uses a tri-mode
load switch (1X), fractional (1.5X), and doubling (2X)
conversion to maximize efficiency for white LED appli-
cations. The device produces current levels up to
30mA on each of its four current source outputs to
drive various arrangements of LEDs from a 2.7V to
5.5V input. Outputs may be operated individually or in
parallel for driving higher-current LEDs. A low external
parts count (two 1µF flying capacitors and two small
1µF capacitors at V
IN
and CP) make the AAT3140 ide-
ally suited for small battery-powered applications.
The AAT3140 is equipped with AnalogicTech’s unique
AutoBias™ technology which allows individual LEDs
to be powered either by charge pump or battery input,
determined internally and automatically to maximize
the power efficiency even with a large difference in
LED forward voltage.
AnalogicTech's Simple Serial Control™ (S
2
Cwire™)
digital input is used to enable, disable, and set the
LED drive current with a 32-level logarithmic scale
LED brightness control. The AAT3140 has a thermal
management system to protect the device in the event
of a short-circuit condition at an output pin. Built-in
soft-start circuitry prevents excessive inrush current
during start-up. A high charge pump switching fre-
quency enables the use of very small external capac-
itors. In shutdown mode, the device disconnects the
load from V
IN
and reduces quiescent current to less
than 1µA. The AAT3140 is available in the very small
12-pin TSOPJW package.
AAT3140
Features
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ChargePump
™
V
IN
Range: 2.7V to 5.5V
Tri-Mode 1X, 1.5X, and 2X Charge Pump for
Maximum Efficiency and V
F
Coverage
Drives Low-V
F
and High-V
F
Type LEDs
Up to 4, 30mA Outputs
32-Position Logarithmic Scale with Digital
Control
Low Noise Constant Frequency Operation
1MHz Switching Frequency
AutoBias Technology
Small Application Circuit
Regulated Output Current
Automatic Soft Start
No Inductors
I
Q
< 1µA in Shutdown
12-Pin TSOPJW Package
Applications
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Color (RGB) Lighting
Programmable Current Sources
White LED Backlighting
White Photo Flash for DSCs
Typical Application
VIN
C1+
C1
1µF
CP
V
BATTERY
C
IN
1µF
C
CP
1µF
C1-
C2+
C2
1µF
AAT3140
C2-
D1
D2
D3
D4
EN/SET
EN/SET
D4
GND
D3
D2
D1
3140.2005.03.1.1
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ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
