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AAT3141ITP-T1

High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications

Advanced Analogic Technologies 

Functional Block Diagram

AAT3141

High Efficiency 1X/1.5X/2X Charge Pump

for White LED Applications

VIN

Soft Start

Control

1MHz

Oscillator

Voltage

Reference

1x

1.5x

2x

Charge

Pump

C1+

C1-

C2+

C2-

CP

32 x 8 bit

D/A

D1

ROM

D/A

D2

D/A

D3

EN/SET

AS2Cwire

Interface

32 x 8 bit

D/A

ROM

D4

GND

Functional Description

The AAT3141 is a tri mode Load Switch (1X) and

high efficiency (1.5X or 2X) charge pump device

intended for white LED back light applications. To

maximize power conversion efficiency, an internal

sensing circuit monitors the voltage required on

each constant current source output and sets the

load switch and charge pump modes based on the

input battery voltage and the current source output

voltage. As the battery discharges over time, the

AAT3141 charge pump is enabled when any of the

four current source outputs nears dropout. The

charge pump initially starts in 1.5X mode. If the

charge pump output droops enough for any current

source output to become close to dropout, the

charge pump will automatically transition to 2X

mode. Each of the four current source outputs is

independently switched between the battery input

(1X) or the charge pump output (1.5X or 2X)

depending on the voltage at the current source out-

put. Since the LED to LED VF can vary as much as

1 volt, this function significantly enhances overall

device efficiency when the battery input voltage

level is greater than the voltage required at any

current source output.

The AAT3141 requires only four external compo-

nents: two 1µF ceramic capacitors for the charge

pump flying capacitors (C1 and C2), one 1µF

ceramic input capacitor (CIN) and one 0.33µF to

1µF ceramic charge pump output capacitor (CCP).

The four constant current outputs (D1 to D4) drive

four individual LEDs with a maximum current of

30mA each. The EN/SET AS2Cwire serial interface

enables the AAT3141, and sets the current source

magnitudes.

10

3141.2004.07.0.91

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