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