AAT3131
High Efficiency 1X/1.5X Fractional
Charge Pump for White LED Applications
General Description
The AAT3131 is a low noise, constant frequency
charge pump DC/DC converter that uses a dual
mode load switch (1X) and fractional (1.5X) con-
version to maximize efficiency for white LED appli-
cations. The device can be used to produce cur-
rent levels up to 20mA in three of its outputs and
30mA in one of its outputs to drive LEDs from a
2.7V to 5.5V input. Outputs may be operated indi-
vidually or paralleled for driving higher-current
LEDs. A low external parts count (two 1µF flying
capacitors and two small 1µF capacitors at V
IN
and
OUT) makes the AAT3131 ideally suited for small
battery-powered applications.
AnalogicTech's Simple Serial Control™ (S
2
Cwire™)
interface is used to enable, disable, and set the LED
drive current in two groups: the three 20mA outputs
and the single 30mA output with multiple level loga-
rithmic scales. The AAT3131 has a thermal man-
agement system to protect the device in the event of
a short-circuit condition at the 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
capacitors. A low-current shutdown feature discon-
nects the load from V
IN
and reduces quiescent cur-
rent to less than 1µA. The AAT3131 is available in
a Pb-free 12-pin TSOPJW12 package and is rated
over the -40°C to +85°C temperature range.
Features
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ChargePump
™
V
IN
Range: 2.7V to 5.5V
<1.0µA of Shutdown Current
1MHz Switching Frequency
White LED Backlighting
Fully Independent Display Lighting
Dual Mode 1X and 1.5X Charge Pump for
Maximum Efficiency
Drives Low-V
F
and High-V
F
Type LEDs
Up to Three 20mA Outputs
Single 30mA Output
Multi-Position Logarithmic Scale with Digital
Control
Low Noise Constant Frequency Operation
Regulated Output Current
Automatic Soft Start
No Inductors
Temperature Range: -40°C to +85°C
12-Pin TSOPJW Package
Applications
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Color (RGB) Lighting
Programmable Current Source
White LED Backlighting
White Photo Flash for Digital Still Cameras
Typical Application
VIN
C1+
C1
1µF
VOUT
V
BATTERY
C
IN
1µF
C
OUT
1µF
C1-
C2+
C2
1µF
AAT3131
C2-
D1
D2
D3
D4
EN/SET
EN/SET
D5
GND
D4
D3
D2
D1
3131.2005.12.1.2
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ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
