AAT3152 datasheet(8/12 Pages) AAT

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AAT3152

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

For White LED Applications

3152.2005.08.1.2

Functional Block Diagram

1X, 1.5X and 2X

Charge Pump

D/A

6 x 16 bit

ROM

6 x 16 bit

ROM

S2Cwire

Interface

Soft-Start

Control

1MHz

Oscillator

Voltage

Reference

VIN

EN/SET

GND

VOUT

C1+

C1- C2+

C2-

Functional Description

The AAT3152 is a tri-mode load switch (1X) and

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

intended for white LED backlight applications. To

maximize power conversion efficiency, an internal

sensing circuit monitors the voltage required on

each constant current sink input and sets the load

switch and charge pump modes based on the input

battery voltage and the current sink input voltage.

As the battery discharges over time, the AAT3152

charge pump is enabled when any of the four cur-

rent sink inputs near dropout. The charge pump ini-

tially starts in 1.5X mode. If the charge pump out-

put drops enough for any current source output to

become close to dropout, the charge pump will

automatically transition to 2X mode. The AAT3152

requires only four external components: two 1µF

ceramic capacitors for the charge pump flying

capacitors (C

1 and C2), one 1µF ceramic input

capacitor (C

IN), and one 0.33µF to 1µF ceramic

charge pump output capacitor (C

OUT).

The four constant current sink inputs (D1 to D4)

can drive four individual LEDs with a maximum cur-

rent of 20mA each. The unused sink inputs must be

connected to V

OUT, otherwise the part will operate

only in 2X charge pump mode. The S

2Cwire serial

interface enables the AAT3152 and sets the cur-

rent sink magnitudes. S

2Cwire addressing allows

independent control of two groups of current sink

input: D1-D3 and D4.

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