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ADS8885: have a louder noise than competitor device

Minghao Yin
Prodigy 365 points
Part Number: ADS8885
Other Parts Discussed in Thread: TIDA-01014, TIDA-01012

Hi team,

Our customer use AD7691 in their board. And we recommend ADS8885 to them.

 Following is ADS8885 schematic diagram, but they found our device noise is louder than ADI device.  

This is ADI AD7691 schmatic diagram.

How to change the schmatic diagram to reduce noise?

Thanks a lot.

  • 0
    TI__Guru**** 168895 points

    Hi Minghao,

    Looks like exactly the same schematic.  Do you have some quantitative detail on this 'louder noise'?  Perhaps some observed SNR or THD details between the two devices?

  • 0 in reply to Tom Hendrick
    TI__Prodigy 365 points

    Actually customer want use our device p2p replace the AD7691. So they use almost the same schematic.

    For customer, thay didn't make test about SNR or THD, they make a test about the whole machine. They found the machine output with a jitter.

    I talk with customer R&D, they found sampling the same signal, ADS8885 last few digits of the sample keep changing. It looks like there is a low-pass filter in the AD7691 but there is no in ADS8885 so that ADS8885 sampling value keep changing.

    It could also be a loop problem.

    So ,please give me a reference design for Ref-OPA-ADC, competitor device is appear in the schmatic.

    And clear is there a low-pass-filter in AD7691 or some block different with ADS8885? If possible please give a recommend resistance and capacity in a stable loop.

  • 0 in reply to Minghao Yin
    TI__Guru 57366 points

    Hello Minghao,

    We have some reference designs featuring ADS8885 on the product folder. TIDA-01012 and TIDA-01014 show examples of input amplifier and reference driver circuits that are used with this ADC.

    https://www.ti.com/product/ADS8885#design-development

    Regards,

    Ryan