EYE ON NPI - Microchip Technology MCP41U83 (Single) and MCP42U83 (Dual) Potentiometers

Adafruit Industries

This week's EYE ON NPI takes a look at a new product with a lot of potential: it's the Microchip Technology MCP41U83 (Single) and MCP42U83 (Dual) Digital Potentiometer series. This family of solid-state potentiometers is ready to replace your mechanical knobs and trimmers: no through hole soldering, and no mechanical failures due to oil, dirt or vibration. With 10-bit resolution, you'll get excellent repeatability and precision for tweaking analog voltages. And, the high 100MHz+ bandwidth means you can use it for filters, audio, sensors, without worry that about losing your signal shape. Potentiometers are trusty mechanical-to-electrical components, used in almost every design to convert mechanical motion - both linear and rotational - to an electronic signal that can easily be measured. They're inexpensive, available in thousands of configurations (https://www.digikey.com/en/products/category/potentiometers-variable-resistors/5): linear or logarithmic, panel mount or SMT, single or dual, linear or rotational, in values from 1 ohm up to 1 Meg. They all pretty much work the same way, with a strip of conductive material such that from end-to-end the resistance is the total 'range' of the pot, and a wiper that literally wipes across from one end to another. Pots can be easily configured as voltage dividers by putting a signal across the two ends and then 'tapping' in to the wiper. Or, they can be rheostats (https://en.wikipedia.org/wiki/Potentiometer#Rheostat) where only one end and the wiper are used to make a variable resistor value. We love pots and trimmers and use them all the time, but they have serious down-sides. Over time, the wipers eventually scrape through the conductive material creating 'scratchy' pots that jump around in value. Or, oil and dust get in and gunk up the internals (https://www.youtube.com/watch?v=AUMxFIH5BN8). They can also drift over time or with humidity so that the center isn't really centered anymore. Also, if your product gets moved around, the knob can get bumped or if its a trimmer, it can get shifted from the vibration (https://forum.digikey.com/t/potentiometer-locking-adhesive-goop/50757) - for that reason if you open up a product with trimmers often times they are dabbed with wax or glue to keep them 'set' (https://www.digikey.com/en/products/detail/mg-chemicals/4228A-55ML/17884735). Thus the genius of digital pots! The Microchip Technology MCP41U83 (https://www.digikey.com/short/wt3zwnq5) and MCP42U83 series chips can replace the mechanical versions while providing I2C or SPI interface for configuration. Unlike many digital pot chips we've used in the past, the MCP41U83 (https://www.digikey.com/short/wt3zwnq5) has 10-bits of resolution for 1024 positions - most top-out at 7-bits or 128 positions! That means you'll actually get better resolution and repeatability than a mechanical pot. Also, many digipots lose their value when power cycled, but the MCP41U83 (https://www.digikey.com/short/wt3zwnq5) comes with internal non-volatile memory so once you've settled on a value you can save it semi-permanently. Note that the NVRAM is rated for 1000 cycle writes so just be aware you can't write to it continuously. The MCP41U83 (https://www.digikey.com/short/wt3zwnq5) comes with both I2C and SPI interfaces. For I2C there are two address pins so you can select up to 4 addresses. For SPI, the pots can be 'daisy-chained' together for up to 128 without needing separate CS lines for each one. For power/logic you can use 2.7~5.5V. If you happen to want to use this for a split supply, you can but the split voltages will still need to be no more than -2.75 and +2.75V. A nice specification we noted in the datasheet is the high bandwidth, with tens-of-MHz even at 100Kohm - this makes it a fine substitute for trimmers in analog settings where signal is passing through the pot such as filters or op-amp circuits. For times when you have stereo signals you want to manage at the same time, there's also the MCP42U83 (https://www.digikey.com/short/hcqj8nn2) which has dual separated pots inside. Both configurations come in both QFN and TSSOP packages, for easy pick-and-placing. We really like the ease and simplicity of these digital potentiometers with good documentation and just enough features to solve common engineering requirements. Whether you need the signal channel MCP41U83 (https://www.digikey.com/short/wt3zwnq5) or dual MCP42U83 (https://www.digikey.com/short/hcqj8nn2), 5K or 100K, QFN or TSSOP. DigiKey has the full series in stock (https://www.digikey.com/short/wz13wpp5) right now for immediate shipment! Order today and you can start integrating these components into your next design by tomorrow afternoon.