How to use a digital potentiometer to calibrate and control an adjustable power supply.
A resistive feedback network is often used to set the output voltage of a power supply, since fixed resistors are simple to use and low cost. However, because a fixed network is not adjustable, the output voltage cannot be accurately set. Therefore, many power supplies use a mechanical potentiometer (pot) in the feedback network to set the output voltage. For easier automatic calibration, a mechanical potentiometer can be replaced with a digital potentiometer. Digital potentiometers are smaller, do not move significantly with age or vibration, and can even be recalibrated remotely. This application note explains some of the calculations required to use a digital potentiometer in this way and also provides a spreadsheet for easy calculations.