LTC3452

Synchronous Buck-Boost MAIN/CAMERA White LED Driver

* High Efficiency: ≥85% Over Entire Li-Ion Battery Range

* Wide VIN Range: 2.7V to 5.5V

* Independent MAIN/CAMERA Current Control

* Up to 425mA Continuous Output Current

* Internal Soft-Start

* Open/Shorted LED Protection

* PWM Brightness Control

* LED Current Matching Typically <2.5%

* Constant Frequency 1MHz Operation

* Low Shutdown Current: 6.5µA

* Overtemperature Protection

* Small Thermally Enhanced 20-Lead (4mm × 4mm) QFN Package

The LTC3452 is a synchronous buck-boost DC/DC converter optimized for driving two banks of white LEDs from a single Li-Ion battery input. Five parallel LEDs can be driven at up to 25mA each in the low power LED bank, while two LEDs can be driven at up to 150mA each (or a single LED at 300mA) in the high power LED bank. 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 by sensing which LED requires the largest forward voltage drop at its programmed current, and regulating the common output rail for lowest dropout. Efficiency of 85% can be achieved over the entire usable range of a Li-Ion battery (2.7V to 4.2V). Maximum LED current for each LED display is programmable with a single external resistor. Dual enable pins allow for PWM brightness control in the low power bank and independent on/off control for the high current bank (optimal for LED camera flash). In shutdown, the supply current is only 6.5µA.

A high constant operating frequency of 1MHz allows the use of a small external inductor. The LTC3452 is offered in a low profile (0.75mm) thermally enhanced 20-lead (4mm × 4mm) QFN package. Applications

* Cell Phones

* Digital Cameras

* PDAs

* Portable Devices