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Problem in AD7725 operation at input Frequency between 9.12MHz to 9.3MHz-Need Immediate Support

Hi,

       We are using AD7725 with Bipolar configuration and loaded Default Filter configuration .We are feeding the External clock for its operation from 5MHz to 10MHz to its clkin pin.we have tied XTALOFF to high and disabled the XTAL functionality.

    In that we found that the ADC is not working at the particular input freq range between 9.12Mhz to 9.3Mhz.i.e we are getting wrong sample values.Except this frequency range(9.12MHz to 9.3MHz) all other input frequency range ,ADC is working fine.

        Is there any thing related to post processor characteristics.we have tried this on 6 ADC's mounted on different boards,we are observing the same problem.

   We have checked the PCB clock routing and measuring the clock at the input Clk pin of ADC.There is no problem. Please help.

Regards,

Jagadish

  • Hello Jagadish,

    you say that the AD7725 malfunctions when the master clock is between 9.12MHz and 9.3MHz. Can you confirm that the part is still converting i.e. can you read back conversions when the clock is between 9.12MHz and 9.3MHz. If you can read the conversions, what is the value of the conversion. What analog input is being applied to the AD7725.

    Regards,

    Mary.

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