General Description
The MAX1649/MAX1651 BiCMOS, step-down, DC-DC switching controllers provide high efficiency over loads ranging from 1mA to more than 2.5A. A unique, current limited pulse-frequency-modulated (PFM) control scheme gives these devices the benefits of pulse-width-modulation (PWM) converters (high efficiency at heavy loads), while using only 100µA of supply current (vs. 2mA to 10mA for PWM converters). Dropout performance down to 300mV is provided by a high switch duty cycle (96.5%) and a low current-sense threshold (110mV).

Features
♦ More than 90% Efficiency (10mA to 1.5A Loads)
♦ More than 12.5W Output Power
♦ Less than 0.3V Dropout Voltage at 500mA
♦ 100µA Max Quiescent Supply Current
♦ 5µA Max Shutdown Supply Current
♦ 16V Max Input Voltage
♦ 5V (MAX1649), 3.3V (MAX1651), or Adjustable
   Output Voltage
♦ Current-Limited Control Scheme
♦ Up to 300kHz Switching Frequency
♦ Up to 96.5% Duty Cycle

Applications
   PDAs
   High-Efficiency Step-Down Regulation
   5V-to-3.3V Green PC Applications
   Battery-Powered Applications