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LMP90100: LMP90100 2 RTD CONNECTİON

Part Number: LMP90100
Other Parts Discussed in Thread: ADS124S08
I want to read values ​​from 2 RTDs using LMP90100 AFE software. But it cannot separate the current sources as two different channels. If I make another connection like 3-Wire RTD using 1 Current Source in LMP90100 datasheet, can I provide measurement?
Thanks
  • Hi ASSA,

    The LMP90100 EVM & software are not intended for use with all different RTD configurations. It should be possible to flywire two RTDs to the board, but this will not work with the software unfortunately.

    I'm sorry, I did not understand the second question about the 3-wire RTD using 1x IDAC. Are you asking if this is possible with the EVM? You should be able to implement this just by disabling IEXC2 (removing the appropriate jumper on JP11). You would also have to take a second measurement between VIN1 and VIN6 on JP11. Again, the EVM is not really setup for this (taking two measurements back to back and calculating the difference), so you would need to use your own software for this RTD configuration.

    -Bryan

  • Hi Bryan,

    My problem is exactly as follows: I want to take measurements using 3-wire 2 Rtd. Instead of the development card, I have only the LMP90100 integrated. I have provided two identical connections like Typical Application 10.2.2 in the LMP90100 datasheet. How can i set it? I have an additional question. In the sample codes on the LMP90100 page, there are only examples of writing and reading register values, but I could not find a sample code to make sense of the data received from the ADC channel. Can you help with this?

  • Hi ASSA,

    Thanks for clarifying. Are you saying that you want to measure two 3-wire RTDs with the LMP90100? If so, I can point you to our RTD cookbook for how to connect multiple 3-wire RTDs to an ADC. You can modify this to fit the LMP90100: https://www.ti.com/lit/an/sbaa275/sbaa275.pdf. Specifically check out Section 2.10 on page 31.

    This section also provides pseudo-code for how to configure the ADC for the 3-wire RTD measurements, as well as how to convert the ADC's output code to a temperature. You should be able to convert this information into workable code.

    I will also point out that the ADS124S08 is the next-next-generation version of the LMP90100 if you still have the option of upgrading to a different ADC. The ADS124S08 has more features, more channels, faster data rates, lower power, lower noise, better DC performance, smaller size and similar cost compared to the LMP90100. If you can, you should consider the ADS124S08 for this design as well as any of your future designs.

    -Bryan

  • Hi Bryan,

    Thanks for your help.This answer was helped for me.

    Best Regards,