• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 450 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS8698: ADS8698 temperature issue

Kumar Swamy45
Prodigy 35 points
Part Number: ADS8698

I am using ADS8698 ADC using SPI and working correctly at ambient temperature. But when I operate at 71'c, the device reads approximately double range constant output even the input is varied. Please help to solve this issue. It's urgent.

Thank you.

  • 0
    TI__Expert 4405 points
    Kumar Swamy,

    Welcome to the TI E2E forum.

    It looks like you have marginal timing on your SPI interface.

    The ADS8698 launches data on the falling edge of SCLK and ideally this should be captured by the host on the next rising edge. But this could vary based on trace lengths and buffers in the path of these two signals. Oscilloscope captures of SDO and SCLK right at the host pins, at 25C and 75C will clearly show this phenomenon.

    Moving the capture instance later by half an SCLK cycle should fix the problem, but it is best to observe the two signals on the scope first.

    Regards,
    Sandeep
  • 0 in reply to Sandeep Kasargod
    Prodigy 35 points
    Hi Sandeep,
    Thanks for your reply.
    Now I have a problem with ADC that I can read all the 7 channels correctly at 71C, but the 8th channel is creating problem. The input at 8 th channel is 5V and it is showing 6V at 71C. I have measured the input at 71c and it is showing 5V correctly. Please suggest solution. It is urgent.

    Thanks and regards,
    Kumar
  • 0 in reply to Kumar Swamy45
    TI__Expert 4405 points

    Kumar Swamy,

    Now that you are getting correct data from 7 of the 8 channels, you have probably fixed the timing issue.

    Could you share the schematics of the circuit that drives the analog input to the 8th channel ? A screenshot of the interface signals would help as well.

    Regards,

    Sandeep

  • 0 in reply to Sandeep Kasargod
    Prodigy 35 points

    Actually, i cant share the schematics due to other problems. But the input to ch1 is from a dc-dc converter of 5v which is constant at high temperature also. But the device is reading 6v.

    there is no components between channel and dc - dc converter

    regards

    kumar