Customer:
I’m looking for a digipot that can go down to the 0 ohm range with a step resolution of around 5-10 ohms. The 0-5k 7bit digipot is close but not quite enough.
Do you have any variants or can custom digipots be built? For example:
– a 10 bit version of the 0-5k ohm digipot would give a resolution of 4.88 ohm steps
– the existing 7bit version with reduced range of 0–1k ohm (instead of 0-5k ohm) would yield a resolution of 7.8 ohms per step
I’m trying to simulate the analogue output of an NTC thermistor with decent resolution without using a DAC setup, which adds lots of complexity.
Originally submitted via email support on 18 May 2025. Migrated to the forum for community visibility.
Soldered Support:
We don’t have plans to make custom versions. You can technically use the breakout board and replace the digipot IC with one that meets your specifications.
Alternatively, you could wire multiple digipots in series to create a cascade that offers more control. Connecting multiple pots in parallel is also technically possible—since we have a 5k minimum, this could work for achieving a 0 to 1k range. An electrical engineering solution like this could apply to your use case.
You might also consider your microcontroller’s analog output or PWM, which can provide very specific voltage output control.
Customer:
I now understand the limitation better. The crux of the challenge in simulating an analogue resistance from an NTC sensor is when you need to get into the 0-100 ohm range total resistance. All solid state digipot wipers are typically 70+ ohms as the lowest they will go.
I think a viable solution is to have parallel digipots, which can be harmonised to provide resistance combinations to get down to those low total resistances below that of a single wiper minimum—for example, 14 ohms. I’m thinking of having a 32bit microcontroller that algorithmically solves for 1/Rt = 1/R1 + 1/R2 to hit a target resistance.
I’ve also realised I can just use a fixed resistor in parallel to a single high resolution digipot, and if I select it correctly I can potentially still hit the target range at the resolution I need.
Soldered Support:
Your proposed solution with parallel digipots is definitely viable. Good luck with your project.