AAT3172 datasheet(8/15 Pages) AAT

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AAT3172

High Current LED Flash Driver Charge Pump IC

3172.2006.05.1.5

Functional Description

The AAT3172 is a high efficiency, low noise, dual

stage tri-mode 1X/1.5X/2X charge pump device

intended for photo-flash LED applications. The

AAT3172 requires only four external components:

two 1.0µF ceramic capacitors for the charge pump

flying capacitors, one 4.7µF ceramic capacitor for

CIN, and one 2.2µF ceramic capacitor for COUT.

The charge pump is designed to deliver load cur-

rents up to 600mA. The dual stage charge pump

section contains soft-start circuitry to prevent

excessive in-rush current during start-up. System

efficiency is maximized with a tri-mode, dual stage

charge pump topology. The internal clock oscilla-

tor, which operates at 1MHz, allows the use of

small external components.

The tri-mode charge pump architecture optimizes

power conversion efficiency. Depending upon the

combination of load current, input voltage, and

nominal LED forward voltage, the charge pump will

operate in a 1X, 1.5X, or 2X mode to generate the

output voltage required to power the load for a pro-

grammed constant current setting. This results in

significant power savings over voltage doubling

architectures, especially when the LEDs are con-

tinuously operated at lower current levels in movie

viewing or flashlight modes.

Constant Current Channels

The AAT3172 contains two programmable constant

current sinks for integrated flash circuit control.

Efficiency is optimized with the low dropout char-

acteristic of the current sinks. The low dropout per-

formance extends the battery operating range for

1X and 1.5X modes, improving efficiency and

extending battery life. Each constant current sink is

3172.2006.05.1.5

Functional Block Diagram

Charge Pump

Section 1

Charge Pump

Section 2

1MHz

Oscillator

Soft Start

Control

C1+

C1-

C2+

C2-

OUT

GND

EN/SET

VIN

System Control;

AS2Cwire

AAT3172 Datasheet(PDF) 8 Page - Advanced Analog Technology, Inc.

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