www.fairchildsemi.com

REV. 1.0.2 5/30/03

Features

• Parallel LED Driver Supports All Forward Voltages

• Internally Matched LED Current Sources

• No External Components Needed to Set LED Current

• Built-in Charge Pump has Three Modes of Operation:

• Up to 86% Efficiency

• Low EMI, Low Ripple

• Up to 80mA Output Current (4

× 20mA)

• Built-in DAC for Digital or PWM Brightness Control

• Can be Duty Cycle Modulated between 0 to 18mA

• 2.7V to 5.5V Input Voltage Range

• 1MHz Operating Frequency

• Shutdown Isolates Output from Input

• Soft-Start Limits Inrush Current

• Short Circuit Protection

• Minimal External Components Needed

• Available in a 14-lead TSSOP Package

• Available in a 16-lead MLP Package

Applications

• Cell Phones

• Handheld Computers

• PDA, DSC, MP3 Players

• Keyboard Backlight

• LED Displays

Description

The FAN5609 generates regulated output current from a

battery with input voltage varying between 2.7V to 5.5V.

Switch reconfiguration and fractional switching techniques

are utilized to achieve high efficiency over the entire input

voltage range. A proprietary internal circuitry continuously

monitors each LED current loop and automatically adjusts

the generated output DC voltage to the lowest minimum

value required by the LED having the highest forward

voltage. This adaptive nature of the FAN5609 eliminates the

need for LED pre-selection (matching) and ensures opera-

tion at high efficiency. When the input voltage is sufficiently

high to sustain the programmed current level in the LEDs,

the FAN5609 re-configures itself to operate as a linear

regulator, and the DC-DC converter is turned off. An internal

two-bit digital to analog converter provides programmability

of the output currents. Only two 0.1µF bucket capacitors and

two 4.7µF input/output capacitors are needed for proper

operation.

Soft-start circuitry prevents excessive current draw during

power on. The device has built-in short circuit protection.

FAN5609

LED Driver with Adaptive Charge Pump DC/DC

Converter

Typical Application

CAP1

CAP2

LED-

LED-

LED-

LED-

V

OUT

GND

FAN5609

IN B

IN A

D

A

C

CAP+

CAP+

CAP-

CAP-