AAT3132/32A
High Efficiency 1.5X Fractional Charge
Pump for White LED Applications
General Description
The AAT3132/32A is a low noise, constant frequen-
cy charge pump DC/DC converter that uses frac-
tional (1.5X) conversion to maximize efficiency for
white LED applications. The device can be used to
produce current levels up to 20mA in three of its out-
puts and up to 25 or 30mA in one of its outputs to
drive LEDs from a 2.7V to 5.5V input. Outputs may
be operated individually or paralleled for driving
higher-current LEDs. A low external parts count
(two 1µF flying capacitors and two small 1µF capac-
itors at V
IN
and OUT) makes the AAT3132/32A ide-
ally 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 AAT3132/32A has a thermal
management 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 switch-
ing frequency 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 device also integrates a
test current/auto-disable feature for each channel.
The AAT3132/32A is available in the very small, Pb-
free, 12-pin TSOPJW package.
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
Drives Low-V
F
and High-V
F
Type LEDs
Up to Three 20mA Outputs
Single 25mA Output (AAT3132-1)
Single 30mA Output (AAT3132/32A)
Multi-Position Logarithmic Scale with Digital
Control
Low Noise Constant Frequency Operation
Regulated Output Current
Automatic Soft Start
No Inductors
-40°C to +85°C Temperature Range
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
AAT3132
C2-
D1
D2
D3
D4
EN/SET
EN/SET
D5
GND
D4
D3
D2
D1
3132.2005.12.1.4
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ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
