White LED Driver in SC70 with Integrated Schottky

The LT3491 is a fixed frequency step-up DC/DC converter specifically designed to drive up to six white LEDs in series from a Li-Ion cell. Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors. The device features a unique high side LED current sense that enables the part to function as a “one wire current source;” one side of the LED string can be returned to ground anywhere, allowing a simpler one wire LED connection. Traditional LED drivers use a grounded resistor to sense LED current, requiring a 2-wire connection to the LED string.

The 2.3MHz switching frequency allows the use of tiny inductors and capacitors. A single pin performs both shutdown and accurate LED dimming control. Few external components are needed: open-LED protection and the Schottky diode are all contained inside the tiny SC70 package. With such a high level of integration, the LT3491 provides a high efficiency LED driver solution in the smallest of spaces.

Applications

* Cellular Phones

* PDAs, Handheld Computers

* Digital Cameras

* MP3 Players

* GPS Receivers

* Drives Up to Six White LEDs from a 3V Supply

* High Side Sense Allows “One Wire Current Source”

* Internal Schottky Diode

* One Pin Dimming and Shutdown

* 27V Open LED Protection

* 2.3MHz Switching Frequency

* ±5% Reference Accuracy

* VIN Range: 2.5V to 12V

* Requires Only 1µF Output Capacitor

* Wide 300:1 True Color PWMTM Dimming Range

* 8-Lead SC70 Package

* Low Profile 6-Lead DFN Package (2mm × 2mm × 0.75mm)