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ADS8881EVMV2-PDK: SNR has a huge gap between tested result and datasheet

Lucas Ding
Prodigy 320 points
Part Number: ADS8881EVMV2-PDK
Other Parts Discussed in Thread: ADS8881, REF6045,

             I met a new problem about the test of ADS8881EVMV2, and that is my SNR(tested in “ADS8881 GUI”) is much worse than datasheet.

              Here is my tested conditions:

  1. 2.25 Vp, 1.5kHz full scale sine input.

  2. Sample rate: 20ksps

  3. My analog input is from AP525, and the configurations are showed as follows:

    My tested results are:

    The SNR should be about 100dB in datasheet and my calculated result is about 98dB, but the tested result is so far from above values.

    How does it happen, and what actions can I take to improve the performance?

  • 0
    TI__Prodigy 320 points
    I has failed to insert Figs, and the filter settings are:
    high pass: AC(<10Hz)
    Low pass: AES17
    Weighting: 50us de-emph

    my SNR tested result is 88dB(best value I can test).
  • 0 in reply to Lucas Ding
    TI__Mastermind 49405 points

    Hi Lucas,

    To obtain the performance, a fully-differential signal close to full-scale needs to be used.  Please note the GUI displays the Signal power on the Spectral Analysis page at the bottom right of the screen. The ADS8881EVMV2-PDK is built with the REF6045 (4.5V); therefore a fully-differential signal of about  +/- 4.39V (8.78Vpp or about -0.2dB from full-scale) should provide the performance.

    Other questions:  Is the function generator connected through SMAs J1 and J2? Are you using the balanced output of the APx525 or a different connection?  If possible,  please provide a picture showing the signal function generator connections to the evaluation board. 

    Many Thanks,

    Kind Regards,

    Luis

  • 0 in reply to Luis Chioye
    TI__Prodigy 320 points
    Thanks for your support! I think it's a connection problem.