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