Electronic Design

Digital Potentiometers

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What is a digital potentiometer?

A conventional potentiometer or "pot" is an analog device used to vary, or control, the amount of current that flows through an electronic circuit. It's a mechanical device with a wiper that's used to select the value of the variable resistance desired. A digital potentiometer is either a volatile or nonvolatile device. The former consists of resistors or resistor arrays. It also has other electronic circuit elements like switches, logic gates, multiplexers, and data converters. A nonvolatile device additionally includes memory in the form of EEPROM or a one-time programmable (fuse link) memory. A digital potentiometer can be used to calibrate system tolerances or dynamically control system parameters. Nonvolatile memory parts retain the wiper-setting values after a power cycle from off to on. In addition, fuse link parts offer a one-time program trimmer feature.

What's the primary advantage of a digital potentiometer compared to an analog potentiometer?

Digital potentiometers are excellent cost-effective replacements for mechanical potentiometers because of their robustness. They also have excellent settability, better resolution, and lower noise levels. They're more stable over time. And, their resistance values drift minimally, are more reliable, and allow for remote control. Other advantages include smaller physical size, a lower temperature coefficient of resistance, more resistance range options, and numerous packages to choose from. Since it is a digital device, a designer has the option of using it in either volatile or nonvolatile memory configurations as well.

What are the various digital-potentiometer applications?

Digital potentiometers can be used as a variable low-pass filter, a programmable-gain amplifier, a programmable oscillator, a voltage-to-current converter, and a programmable rise- and fall-time waveform controller. They also can be used for precision calibration of set point thresholds, sensor trimming, LCD bias trimming, audio attenuation, adjustable power supplies, motor-control overcurrent trip setting, and offset trimming.

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