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TIDA-010019: Filter between TMP235 and ADS112U04

Kurumi Hasegawa
Expert 6341 points
Part Number: TIDA-010019
Other Parts Discussed in Thread: TMP235, , ADS112U04, LMT70

Hi team,

 

The datasheet of TMP235 shows how to determine Cfilter and Rfilter when connecting an (SAR) ADC.

However when I was referring TIDA-010019, there is no Cfilter/Rfilter implemented. Why? Is it because ADS112U04 is delta-sigma ADC?

TIDA-010019 has Cfilter and Rfilter between LMT70 and ADS112U04 though.

 

If implementation of Cfilter and Rfilter between TMP235 and ADS112U04 depends on system requirement, how can we determine the value?

I could not find Cmux+Csample equivalent value on ADS112U04’s datasheet.

 

Best regards,

Kurumi

  • +1
    TI__Intellectual 1035 points

    Hi Kurumi,

    the TMP235s datasheet explains that the capacitor is needed to provide enough charge to charge the (SAR) ADCs internal sampling capacitor. If we have a buffered input or there is no sample capacitor as part of the ADC, this is not needed. Another use case could be a low pass filter to reduce noise and as an anti-alias filter. 

    On the TIDA there are place holders to add a filter if needed, however during testing we have seen, that there is no need for this filter in this design. We have no sample capacitor that we need to charge and there are no high frequency components that we need to filter out.

    For the LMT70 I choose to use the recommended circuit for high resolution, figure 35 from the datasheet. I could imaging, that it also works with same performance without the filter network.

    Best regards,

    Steffen

  • 0 in reply to Steffen Graf70
    TI__Expert 6341 points

    Hi Steffen,

    Thank you so much for detailed explanation. I understand.

    Best regards,

    Kurumi