DESCRIPTION

      The AT8854 is a synchronous buck-boost DC/DC converter optimized for driving a single high power LED at currents up to 1A from a single cell Li-lon battery input. The regulator operates in either synchronous buck, synchronous boost, or buck-boost mode depending on input voltage and LED forward voltage. P_LED/P_IN efficiency greater than 90% can be achieved over the entire usable range of a Li-Ion battery (2.7V to 4.2V).

      LED current is programmable to one of four levels, including shutdown, with dual external resistors and dual enable inputs. In shutdown no supply current is drawn.A high constant operating frequency of 1MHz allows the use of small external components. The AT8854 is offered in a low profile (0.75mm) thermally enhanced 10-lead(3mm×3mm) DFN package.

FEATURES

High Efficiency: >90% Typical in Torch Mode, >80% in Flash Mode.

Wide VIN Range: 2.7V to 5.5V

Up to 1A Continuous Output Current

3.5% LED Current Programming Accuracy

Internal Soft-Start

Open/Shorted LED Protection

Constant Frequency 1MHz Operation

Zero Shutdown Current

Over temperature Protection

Small Thermally Enhanced 10-lead (3mm×3mm) DFN Package

APPLICATIONS

Cell Phone Camera Flash

Cell Phone Torch Lighting

Digital Cameras

PDAs

Misc Li-lon LED Drivers

TYPICAL APPLICATION

High Efficiency Torch/Flash LED Driver

LED Power Efficiency vs V_IN

500mA LED Flashlight Driver

DIAGRAM