LINEAR TECHNOLOGY LT3497 User Guide

LT3497

Dual Full Function White LED Driver with Integrated Schottky Diodes

FEATURES DESCRIPTION ■ Drives Up to 12 White LEDs (6 in Series per

The LT®3497 is a dual full function step-up DC/DC con-

Converter) from a 3V Supply verter specifi cally designed to drive up to 12 white LEDs ■ Two Independent Boost Converters Capable of

(6 white LEDs in series per converter) from a Li-Ion cell. Se-

Driving Asymmetric LED Strings ries connection of the LEDs provides identical LED currents ■ Independent Dimming and Shutdown Control of the

resulting in uniform brightness and eliminating the need

Two LED Strings for ballast resistors and expensive factory calibration. ■ High Side Sense Allows “One Wire Current Source”

The two independent converters are capable of driving

per Converter

asymmetric LED strings. Accurate LED dimming and

■ Internal Schottky Diodes

shutdown of the two LED strings can also be controlled

■ Open LED Protection (32V)

independently. The LT3497 features a unique high side LED

■ 2.3MHz Switching Frequency

current sense that enables the part to function as a “one

■ ±5% Reference Accuracy

wire current source;” one side of the LED string can be

■ VIN Range: 2.5V to 10V

returned to ground anywhere, allowing a simpler 1-wire

■ Dual Wide 250:1 True Color PWMTM Dimming

LED connection. Traditional LED drivers use a grounded

■ Requires Only 1µF Output Capacitor per Converter EF FI CI EN CY

resistor to sense LED current, requiring a 2-wire connec-

■ Available in a 3mm × 2mm 10-Pin DFN Package

tion to the LED string. APPLICATIONS The 2.3MHz switching frequency allows the use of tiny inductors and capacitors. Few external components are

■ Cellular Phones

needed for the dual white LED Driver: open-LED protection

■ PDAs, Handheld Computers

and the Schottky diodes are all contained inside the 3mm

■ Digital Cameras

× 2mm DFN package. With such a high level of integra-

■ MP3 Players

tion, the LT3497 provides a high effi ciency dual white LED

■ GPS Receivers

driver solution in the smallest of spaces. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. True Color PWM is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.

TYPICAL APPLICATION Li-Ion Power Driver for 4/4 White LEDs Effi ciency

3V TO 5V VIN = 3.6V 4/4LEDs

SW1 VIN SW2 CAP1 CAP2

LT3497 10Ω10Ω

LED1 LED2 CTRL1 GND CTRL2

3497 TA01a

OFF ON OFF ON

SHUTDOWN SHUTDOWN

LED CURRENT (m A) 3497 TA01b

AND DIMMING AND DIMMING CONTROL 1 CONTROL 2