View max649-max652 datasheet:

19-0225; Rev 3; 9/97 5V/3.3V/3V or Adjustable, High-Efficiency, Low I , Step-Down DC-DC Controllers Q _______________General Description ____________________________Features The MAX649/MAX651/MAX652 BiCMOS, step-down DC- More than 90% Efficiency (10mA to 1.5A Loads) DC switching controllers provide high efficiency over More than 12.5W Output Power three decades of load current. A unique, current-limited 100µA Max Quiescent Supply Current pulse-frequency-modulated (PFM) control scheme gives these devices the benefits of pulse-width-modulation 5µA Max Shutdown Supply Current (PWM) converters (high efficiency at heavy loads), while Less than 1.0V Dropout Voltage using only 100µA of supply current (vs. 2mA to 10mA for 16.5V Max Input Voltage PWM converters). The result is h