General Description

The MAX1573 fractional charge pump drives up to four white LEDs with regulated constant current for uniform intensity. By utilizing proprietary adaptive 1x/1.5x modes and ultra-low-dropout current regulators, it maintains the highest possible efficiency over the full 1-cell Li+ battery input voltage range. The 1MHz fixed frequency switching allows for tiny external components and the regulation scheme is optimized to ensure low EMI and low input ripple.

Features

? Proprietary Adaptive 1x/1.5x Modes

? High Efficiency (PLEDs/PBATT), Up to 92

? 0.2 LED Current Matching

? 28mA/LED Drive Capability

? Low Input Ripple and EMI

? Eliminates Ballast Resistors

? Logic or PWM Dimming Control

? Low 0.1μA Shutdown Current

? 2.7V to 5.5V Input Voltage Range

? Soft-Start Limits Inrush Current

? Output Overvoltage Protection

? Thermal Shutdown Protection

? No External Schottky Diode Required

? Tiny UCSP (2.1mm x 2.1mm x 0.6mm) and Thin

?? QFN (4mm x 4mm) Packages

Applications

?? Cell Phones, Smart Phones

?? PDAs, Digital Cameras, Camcorders

?? MP3 Players

?? Other Handhelds with Color Displays