MAX1570

19-2526; Rev 0; 7/02 www.DataSheet4U.com White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump General Description The MAX1570 fractional charge pump drives up to five white LEDs with regulated constant current for uniform intensity. The MAX1570 maintains the highest possible efficiency over the full 1-cell lithium-ion (Li+) battery input voltage range by utilizing a 1x/1.5x fractional charge pump and very-low-dropout current regulators. The MAX1570 operates with 1MHz fixed-frequency switching, allowing for tiny external components. The regulation scheme is optimized to ensure low EMI and low input ripple. An external resistor sets the full-scale LED current, while two digital inputs control on/off and select between three levels of brightness. A pulse-width modulation (PWM) signal can also be used to modulate LED brightness. The MAX1570 is available in 16-pin 4mm ✕ 4mm Thin QFN packaging (0.8mm max height). o 30mA/LED Drive Capability o Proprietary 1x/1.5x Modes for Ultra-High Efficiency o Low Input Ripple and EMI o Eliminates Ballast Resistors o Digital or PWM LED Dimming Control o 0.1µA Shutdown Current o 2.7V to 5.5V Supply Voltage Range o Soft-Start Limits Inrush Current o Thermal-Shutdown Protection o No External Inductor, Schottky, or Zener Diode Required o Tiny 16-Pin 4mm ✕ 4mm Thin QFN Package Features o Excellent 0.3% LED-to-LED Current Matching MAX1570 Applications White LED Backlighting Cell Phones and Smart Phones PDA and Palmtop Computers Por...