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ADS8548: Why did the Reference voltage change from default 2.5V to 1.031V after ADS8548 was running 2 hour?

Eggsy Pang
Expert 4985 points
Part Number: ADS8548

Hi Team,

        My customer feedback that why did  the Internal Reference voltage change from default 2.5V to 1.031V after ADS8548 was running 2 hour?

       They used ADS8548 default Internal Reference 2.5V. ADS8548 is controlled by FPGA. FPGA never configured ADS8548, it mean ADS8548 all the function is default. The board power up, after ADS8548 running about 2 hour,  Reference voltage change from default 2.5V to 1.031V. When power off  the board and power up again, the Reference voltage is normal, 2.5V.

It looks like so strange. Could you have any suggestions?

Thanks!

       Please see the attached SCH from Customer.

  • 0
    TI__Mastermind 40615 points

    Hello Eggsy,

    Thanks for query on E2E. Is there only one ADS8548 on the board? Did the customer monitor /STBY signal? Can you please ask the customer to do following tests?

    1. Add a pull up resistor to BVDD on /STBY pin.

    2. Change pull down resistors to 0ohm (R34, R35,R45,R66)

    3. Short AGND and DGND directly without inductor

    4. Add a pull down resistor(~10kohm) on RESET pin (apply a reset pulse signal after power up ADC)

    Please let me know the experiment results.

    Thanks&regards

    Dale

  • 0 in reply to Dale Li
    TI__Expert 4985 points

    Hi Dale,

          Thanks for your help!

     I will call customer to monitor /STBY signal when ref voltage is changed to 1.031V.

    As for following test you gave, does it mean I need to do that at the same time or do that one by one?

    Thanks again!

    Best Regards,

    Eggsy.   

  • 0 in reply to Eggsy Pang
    TI__Mastermind 40615 points

    Hello Eggsy,

    Please do it one by one and check every step, also please keep previous changes for current and next step check. Thanks.

    Best regards

    Dale

  • 0 in reply to Dale Li
    TI__Expert 4985 points

    Hi Dale,

         Thanks for your help.

    Customers have a question that what is the different  "Short AGND and DGND directly"   with   "connect AGND and DGND with inductor" ?

    Do you have any idea?

    Best regards,

    Eggsy.

  • 0 in reply to Eggsy Pang
    TI__Mastermind 40615 points
    Hi Eggsy,
    I apologized for late response and I just came back from vacation, I will call you directly to solve the issue tomorrow.

    Best regards
    Dale