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