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Resolution and SNR of the ADS1282

Robert 54013
Prodigy 20 points
Other Parts Discussed in Thread: ADS1282

Dear Community

I'd like to know how a resolution of 31bit can be specified while the SNR is 130dB (=21.5Bit). I'm even more interested how I could prove it.

Thanks for any answer.

  • 0
    TI__Intellectual 1600 points

    Hi Robert,

     

    The ADS1282 is an ADC specifically for low frequency vibrational (e.g. seismic) measurement.  The device has a delta-sigma ADC architecture which can generate many more bits of resolution than the theoretical limit based on the input noise level.  In the case of the ADS1282, 32 bits of resolution are generated as a convenience for some systems that the device goes into.  

    It is not a performance metric that could be proven.  Instead, it is simply a feature of the device. The user could stop clocking out data after 24 bits, 3 bytes rather than 4bytes, with no degradation in performance.

     

    Rudye

  • 0 in reply to RudyeM
    Prodigy 20 points

    Dear Rudye

     

    Thanks for the answer. I'm actually in the seismic business. Did any one ever prove that resolution in your lab. How high was the resolution you could actually measure. And do you hav a measurement setup to measure its linearity short of applying a high accurate dc source and a A/D converter which higher lineariyt as a reference?

     

    Thanks

     

    Robert

  • 0 in reply to Robert 54013
    TI__Intellectual 1600 points

    Hi Robert,

    The spectral plots on pages 7 and 8 of the datasheet represent typical measurements from the bench setup.  The actual performance of the data converter, in terms of resolution, can be calculated using the SNR information measured from these plots.  As I mentioned in my previous post, the 4th byte of information from the device is purely a convenience provided for some system architectures and provides no additional information.  

    As to the linearity measurement, you have it correct.  The measurement is made by first measuring a very steady, very low noise voltage with a high precision reference ADC.  Then, that voltage is introduced the the ADS1282, and the two measurements are compared.  

    Rudye