5V/3.3V/3V Adjustable, High-Efficiency, Low-I, Step-Down DC-DC Converters

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.

The MAX639/MAX640/MAX653 input range is 4V to 11.5V, and the devices provide lower preset output voltages of 5V, 3.3V, and 3V, respectively. Or, the output can be user-adjusted to any voltage from 1.3V to the input voltage.

The MAX639/MAX640/MAX653 have an internal 1A power MOSFET switch, making them ideal for minimum-component, low- and medium-power applications. For increased output drive capability, use the MAX649/MAX651/MAX652 step-down controllers, which drive an external P-channel FET to deliver up to 5W.

Applications

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

* 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