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PGA280 Distortion above 20kHz

Adrian Helwig
Expert 3860 points
Other Parts Discussed in Thread: PGA280

Hello

My customer has following issue:

They observe signal distortion above 20kHz when they set the PGA280 gain to 1/8. See attached file.

Is this behavior normal case? or what could be the cause for it?

PGA280_distortion.pdf
  • 0
    TI__Guru* 94295 points

    I got this response from the designer:

    ***

    Yes, we have seen distortion at large signals with increasing frequency.   This is at a little bit lower frequencies than what we have seen, but still in the ballpark.  It has to do with the general architecture of the part.  As the topology strongly relies on current conservation for accuracy at higher frequencies parasitic capacitances lead to loss of current that show up as distortion on the signal.  

    ***

    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Expert 3860 points

    Thanks for Your answer.

    So, it seems to be known issue with PGA280. My question will be now waht are the maximum rating for signal frequency and aplitude to avoid distortion. Can I find some recomendations in the data sheet? or waht can we do generally to avoid this distortion?

    Thanks

    Adrian

  • 0 in reply to Adrian Helwig
    TI__Guru* 94295 points

    Adrian,

    Currently, we don't have too much data on this phenomenon. However the development team is interested in who the customer is, what the application is and what the potential volumes are.

    However, I would point out that since the distortion is above 20kHz, it is typically far above the usable frequency response of the digital filter in most of the oversampling converters in the product line.

    Joseph Wu