AAT3140_07 Datasheet, PDF(10/16 Page) Advanced Analogic Technologies – High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications

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AAT3140_07 Datasheet, PDF (10/16 Pages) Advanced Analogic Technologies – High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications

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Functional Block Diagram

AAT3140

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

for White LED Applications

VIN

Soft-Start

Control

1MHz

Oscillator

Voltage

Reference

1.5X

Charge

Pump

C1+

C1-

C2+

C2-

D/A

EN/SET

S2Cwire

Interface

32 x 8 bit

ROM

D/A

GND

Functional Description

The AAT3140 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 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

AAT3140 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 drops enough for any current

source output to become close to dropout, the

charge pump will automatically transition to 2X

mode.

AutoBias Technology

Each of the four current source outputs is inde-

pendently switched between the battery input (1X)

or the charge pump output (1.5X or 2X), depending

on the voltage at the current source output. Since

the LED-to-LED forward voltage (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 AAT3140 requires only four external compo-

nents: two 1ÂµF ceramic capacitors for the charge

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

ceramic input capacitor (CIN), and one 0.33ÂµF to

1ÂµF 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 S2Cwire serial interface

enables the AAT3140 and sets the current source

magnitudes.

3140.2007.03.1.3

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