MAX1574

19-3117; Rev 0; 12/03 KIT ATION EVALU E L B AVAILA 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN General Description Features ♦ Up to 180mA (60mA/LED) Drive Capability ♦ 83% Average Efficiency (PLED / PBATT) Over Li+ Battery Discharge ♦ 0.5% (typ) LED Current Matching ♦ Adaptive 1x/2x Mode Switchover ♦ Low Input Ripple and EMI ♦ 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 ♦ 10-Pin 3mm x 3mm TDFN Package MAX1574 The MAX1574 charge pump drives up to three white LEDs with regulated constant current for uniform intensity. By utilizing adaptive 1x/2x charge-pump modes and very-low-dropout current regulators, it achieves 180mA output drive capability and high efficiency over the 1-cell lithium-battery input voltage range. Fixed-frequency (1MHz) switching allows for tiny external components, and the regulation scheme is optimized to ensure low EMI and low input ripple. The MAX1574 uses an external resistor to set the fullscale 100% LED current. An enable input (EN) is used for simple on/off control or can be pulsed repeatedly to set lower LED current in multiple steps down to 5%. Once the desired brightness is set, the MAX1574 maintains constant LED current as long as EN is kept high. If EN is kept low for more than 2ms, the MAX1574 enters shutdown. The MAX1574 is available in a 10-pin 3mm x 3m...