AAT3194

High Efficiency 1.5X Fractional Charge Pump For White LED Applications

PRODUCT DATASHEET

3194.2008.05.1.1

1

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General Description

The AAT3194 is a low noise, constant frequency charge

pump DC/DC converters that use fractional (1.5X) conver-

sion to increase efficiency in white LED applications. The

devices can be used to produce current levels up to 20mA

for each output from a 2.7V to 5.5V input. A low external

parts count (two 1µF flying capacitors and two small

bypass capacitors at IN and OUT) makes these devices

ideally suited for small, battery-powered applications.

face is used to enable, disable, and set the LED drive

current for 32-level logarithmic scale LED brightness

control. The AAT3194 has a thermal management sys-

tem for protection in the event of a short-circuit condi-

tion on any of the output pins. Built-in soft-start circuitry

prevents excessive inrush current during start-up. A high

switching frequency enables the use of small external

capacitors. A low-current shutdown feature disconnects

than 1µA. The AAT3194 is available in a Pb-free 12-pin

TSOPJW package.

Features

• 20mA Full-Scale Current

• Low Noise Constant Frequency Operation

• 33% Less Input Current Than Doubler Charge Pump

• High Accuracy Brightness Matching

• Small Application Circuit

• Regulated Output Current

• Automatic Soft Start

• No Inductors

• 600kHz Switching Frequency

• Temperature Range: -40°C to 85°C

• 12-Pin TSOPJW Package

Applications

• Programmable Current Source

• White LED Backlighting

Typical Application

1µF

1µF

EN/SET

C1

1µF

C2

1µF

D4

D3

D2

D1

IN

OUT

C1+

C1-

C2+

C2-

D1

D2

D3

D4

EN/SET

GND

AAT3194