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ADS1255: incorrect output code (FFFFFC) output

Shinichi Inoue
Guru 21646 points
Part Number: ADS1255

Dear Specialists,

My customer is encountering incorrect output code.

I would be grateful if you could advise.

---

Regarding "ADS1255"

Although the AD conversion completion signal is normally output, the event that the output becomes "FFFFFC" becomes constant.

It output correctly at the time of shipment, but after 1 month passed, the output became not correct.

This causes only one device. 

What reason can be considered?

---

I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Guru**** 180931 points

    Hi Shinichi-san,

    You need to provide a little more detail here. Are you saying that no matter what the input voltage, the output code is always "FFFFFC"? If that is the case, it sounds like the part may have been damaged somehow. Do you know what the environmental conditions were at the time the output code became stuck? Were there any voltage surges? What is connected to the ADC inputs? Is the voltage reference correct? Can you share a schematic?

  • 0 in reply to Tom Hendrick
    Guru 21646 points

    Hi Tom,

    Thank you for your reply.

    I'll confirm the environment and schematic with the customer and feedback.

    I appreciate your great help.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    Guru 21646 points

    Hi Tom,

    I could get the customer's situation.

    Could you please see below.

    ---

    The device was used in the cleanroom at the condition of 23deg and 50%RH.

    The input is stable analog voltage(temperature sensor and amp)

    The possibility of voltage surge is quite low.

    Because we produced 20k and this failure is only one. 

    SCLK, DIN, DOUT are isolated.

    Reference voltage may be no problem, because ADS1255 has changed, it can output correct data.

    Could you please advise other possibility?

    ---

    I appreciate your great help.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Guru**** 180931 points
    Hi Shinichi,

    Based on your comments, I'm not sure that there is anything we can do to resolve this short of sending the device in for failure analysis. I suspect it would come back as an EOS failure.