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50/60Hz Noise Rejection, ADS1248

G Hann
Prodigy 560 points

Hey Guys,

 

I was at a dataconverter seminar in Mil and we were looking for a deeper dive into understanding 50/60Hz rejection. The specific question is if the sample rate is associated with the 50/60Hz filter. Do you know if we have any good deep dives into this topic that we can share with him to give him a better understanding?

 

Thanks,

Gina

 

  • 0
    TI__Prodigy 560 points

    Response from some of our team members:

    Gina,

    Yes, the sample rate is associated to 50/60Hz rejection in that generally only certain datarates less than 50/60SPS offer strong attenuation. Depending on the type of filter used, different data rates may have 50/60Hz rejection capabilities. TI has a distinct advantage in data rate with 50 & 60Hz rejection - we can run at 20SPS with single-cycle settling where others can only get to 16SPS  - we are 25% faster which is a big deal when you are scanning through a lot of inputs.  The design of the digital filter has a lot to do with this, and we have a custom finite impulse response (FIR) digital filter that is optimized for speed while still providing 50 & 60 Hz rejection. 

    As a starting point, our ADS1248 family offers excellent 50/60Hz rejection with this FIR implementation. In comparison our ADS1231 offers 50/60Hz through a high order sinc filter. You might suggest that starting with those datasheets and looking at the filter plots to gain some understanding.

    Best regards,
    Mike