AAT3132/32A
High Efficiency 1.5X Fractional Charge
Pump for White LED Applications
Functional Block Diagram
VIN
Soft-Start
Control
1MHz
Oscillator
Voltage
Reference
1.5X
Charge
Pump
C1+
C1-
C2+
C2-
OUT
Current
Reference
Quad
Output
DAC
D1
D2
D3
32x16 bit
ROM
EN/SET
S
2
Cwire
Interface
32x16 bit
ROM
Single
Output
DAC
D4
GND
Functional Description
The AAT3132/32A is a high efficiency (1.5X) frac-
tional charge pump device intended for white LED
backlight applications. It consists of a 1.5X charge
pump with multiple current source outputs. To max-
imize power conversion efficiency, an internal feed-
back control sensing circuit monitors the voltage
required on the constant current source outputs.
The AAT3132/32A requires only four external
components: two 1µF ceramic capacitors for the
charge pump flying capacitors (C
1
and C
2
), one
1µF ceramic input capacitor (C
IN
), and one
0.33µF to 1µF ceramic output capacitor (C
OUT
).
The 1.5X charge pump output is converted into
three (D1 to D3) constant current outputs to drive
three individual LEDs with a maximum current of
20mA each, and one (D4) constant current output
with a maximum current of 25 or 30mA. The cur-
3132.2005.12.1.4
7
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