General Description
The MAX639/MAX640/MAX653 step-down switching regulators provide high efficiency over a wide range of load currents, delivering up to 225mA. A current-limiting pulse-frequency-modulated (PFM) control scheme gives the devices the benefits of pulse-width-modulated (PWM) converters (high efficiency at heavy loads), while using only 10µA of supply current (vs. 2mA to 10mA for PWM converters). The result is high efficiency over a wide range of loads.

FEATUREs
♦ High Efficiency for a Wide Range of Load Currents
♦ 10µA Quiescent Current
♦ Output Currents Up to 225mA
♦ Preset or Adjustable Output Voltage:
    5.0V (MAX639)
    3.3V (MAX640)
    3.0V (MAX653)
♦ Low-Battery Detection Comparator
♦ Current-Limiting PFM Control Scheme

APPLICATIONs
    9V Battery to 5V, 3.3V, or 3V Conversion
    High-Efficiency Linear Regulator Replacement
    Portable Instruments and Handy-Terminals
    5V-to-3.3V Converters