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