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ADS8688AT: Anti-aliasing LPF details

Jim Brinkhurst1
Mastermind 44680 points

Part Number: ADS8688AT
Other Parts Discussed in Thread: ADS8688

Hi experts!

My customer has the following question about the ADS8688AT:

We’ve been interested in using AD8688  for some low frequency signal processing.  But, we’d like to do some differencing digitally and are worried about the CMRR achievable when the AA filters in the part aren’t specified tightly.  What I’m wondering is there any test data available of the statistics of the corner frequency and Q factor of the filters?  They are rated nominally as 15kHz, but not with tolerance, min-max, or most useful, matching characteristics.

Can we provide any additional guidance regarding the filter or how to achieve what they're considering?

Best regards,

Jim B

  • 0
    TI__Mastermind 49575 points

    Hi Jim,

    ADS8688 can only support single-ended input analog signal, not differential signal, the AIN_nGND should be restricted to +/-0.3V, this is the reason why there is no CMRR spec in the datasheet. The 15kHz is the -3dB cutoff frequency of 2-order low-pass filter. What's the signal frequency in the customer's system? What's the specific reason the customer is worried about the CMRR?

    Regards,

    Dale