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ADS8568, SNR measurement

Yee Yong Teo
Expert 4335 points
Other Parts Discussed in Thread: ADS8568

Hi,

Questions about ADS8568 SNR measurement:

  1. Is 90dB minimum stated in the datasheet an average value?
  2. If not, during TI validation test, what is the minimum value of SNR result?
  3. How does TI calculate the SNR? Use formula SNR = 20 log (signal/noise) ? Peak signal value or RMS signal value?

Thanks.

- YY

  • 0
    TI__Intellectual 1205 points

    The minimum of 90dB of SNR is the worst case performance over the entire specified temperature range.  Minimums and maximums are tested parameters, and not averages.  Texas Instruments will not ship an ADS8568 that has less than 90dB of SNR. 

    Typical numbers in the datasheets are derived from the statistical distribution of the results, so in this case, most ADS8568's will have an SNR of more like 91.5dB.

    In the test environment, Texas Instruments makes the SNR calculation coherently sampling a signal and processing an FFT.  After excluding the DC offset, all "noise" bins are added (by taking the square root of the sum of the squares of each bin) and compared to the fundamental bin.  After that, your formula is exactly what is used.