General Description
The MAX1575 charge pump drives up to four white LEDs in the main display and up to two white LEDs in the sub-display with regulated constant current for uniform intensity. By utilizing adaptive 1x/1.5x chargepump modes and very-low-dropout current regulators, it achieves high efficiency over the full 1-cell lithium battery input voltage range. A 1MHz fixed-frequency switching allows for tiny external components, and the regulation scheme is optimized to ensure low EMI and low input ripple.

Features
♦ Powers Main and Sub-Display LEDs
♦ 85% Average Efficiency (PLED / PBATT) Over Li+
   Battery Discharge
♦ 2% LED Current Matching
♦ Up to 30mA/LED Drive Capability
♦ Adaptive 1x/1.5x Mode Switchover
♦ Low Input Ripple and EMI
♦ Individual 5% to 100% Dimming Through
   Single-Wire Serial Pulse Interface
♦ Low 0.1µA Shutdown Current
♦ 2.7V to 5.5V Supply Voltage Range
♦ Soft-Start Limits Inrush Current
♦ Output-Overvoltage Protection
♦ Thermal-Shutdown Protection
♦ 16-Pin Thin QFN 4mm x 4mm Package

Applications
   Cell Phones with Main and Sub-Displays
   PDAs/Smart Phones with Up to Six White LEDs