AAT3129_07 datasheet(9/15 Pages) ANALOGICTECH

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AAT3129

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

for RGB Color LED Applications

3129.2007.01.1.4

Functional Block Diagram

Voltage

Reference

Soft Start

1MHz

Oscillator

1.5X

Charge

Pump

AS2Cwire

Interface

Control

C1-

C2+

C2-

ISRC

GND

EN/SET

VIN

C1+

Functional Description

The AAT3129 is a tri-mode load switch (1X) and

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

intended for fashion color LED lighting applications.

To maximize power conversion efficiency, an inter-

nal sensing circuit monitors the voltage required on

the 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

AAT3129 charge pump is enabled when the current

source output nears dropout. The charge pump ini-

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

put drops enough for the current source output to

become close to dropout, the charge pump will

automatically transition to 2X mode.

The AAT3129 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 output capacitor (CP).

The color and brightness of an RGB color LED is

maintained by PWM signals, which are pro-

grammed via the AS2Cwire interface. The control

block generates three gate drive PWM signals for

the N-channel MOSFET switches. Please refer to

the interface description and timing in the following

section for details.

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