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Need a high temperature current loop driver?

Dave McLaughlin
Prodigy 50 points
Other Parts Discussed in Thread: XTR105, XTR117

I have a design using the XTR105UA that measures ambient temperature and I need to find a replacement that can handle ambient temperatures of up to 115C so ideally a 125C rated part. Accuracy is not as important as being able to work at the ambient temperature.

I've checked the parts from IT but I don't see any that are rated for this working temperature.

I need to find a solution that has a small board space as this is installed in a sealed enclosure that has an internal diameter of 25mm. As a test I ran the current design above the working temperature and it failed at 97 deg C.

  • 0
    TI__Guru 63995 points

    Hi Dave,

    The XTR105, 112 and 114 which feature the RTD linearization and current-loop driving circuitry are only rated up to +85C as you've noted.  We don't recommend trying to use them above this temperature because of the issues you experienced around +97C. 

    That said, we can construct a similar circuit discretely using some op-amps and INAs along with the XTR117 which is rated for operating temperatures up to +125C.  It will be difficult to keep the PCB size as small as the XTR105 because it is a fully integrated solution, but let us know if you're interested in pursuing this route and we can work towards a solution. 

  • 0 in reply to Collin Wells
    Prodigy 50 points
    Just for a quick reference, I was able to build a nice small temp sensor board with the XTR117 and an LM35CH with a 2.5V reference also rated for +125C. This has proven to be reliable and accurate enough for this application. Thanks for the initial heads up on the XTR117.