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 MAX639, MAX640 and MAX653 are step‑down switching regulators that deliver high efficiency over a wide range of load currents, with up to 225 mA output current and a quiescent supply current of only 10 µA. They accept an input voltage from 4 V to 11.5 V and offer preset output voltages of 5 V (MAX639), 3.3 V (MAX640) and 3 V (MAX653), or an adjustable output from 1.3 V up to the input voltage.
The datasheet details electrical characteristics, absolute maximum ratings, pin descriptions, typical operating curves, startup time, transient response, and design guidelines such as inductor selection and component recommendations. It also includes ordering information and a list of recommended part numbers for inductors, capacitors, and diodes.
| Input voltage range | 4 V to 11.5 V |
|---|---|
| Maximum output current | 225 mA |
| Quiescent supply current | 10 µA |
| Internal power MOSFET switch rating | 1 A |
| Preset output voltages | 5 V (MAX639), 3.3 V (MAX640), 3 V (MAX653) |
They can deliver up to 225 mA of output current.
The quiescent supply current is only 10 µA.
They operate with an input voltage from 4 V to 11.5 V.
The output can be adjusted to any voltage between 1.3 V and the input voltage using an external voltage divider on the VFB pin.