DESCRIPTION
The LTC®3453 is a synchronous buck-boost DC/DC converter optimized for driving up to 4 white LEDs at a combined current of up to 500mA from a single Li-Ion battery input. The regulator operates in either synchronous buck, synchronous boost, or buck-boost mode, depending on input voltage and LED maximum forward voltage. Optimum efficiency is achieved using a proprietary architecture that determines which LED requires the largest forward voltage drop at its programmed current, and regulates the common output rail for lowest dropout. Efficiency of 90% can be achieved over the entire usable range of a Li-Ion battery (2.7V to 4.2V).

FEATURES
■ High Efficiency: 90% Typical Over Entire Li-Ion Battery Range
■ Wide VIN Range: 2.7V to 5.5V
■ Up to 500mA Continuous Output Current
■ Internal Soft-Start
■ Open/Shorted LED Protection
■ LED Current Matching Typically <2%
■ Constant Frequency 1MHz Operation
■ Low Shutdown Current: 6µA
■ Overtemperature Protection
■ Small Thermally Enhanced 16-Lead (4mm x 4mm) QFN Package

APPLICATIONS
■ Cell Phones
■ Digital Cameras
■ PDAs
■ Portable Devices