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ADS1271 Gain or Offset shift at higher temperature

yehuda mermelstein
Prodigy 70 points
Other Parts Discussed in Thread: ADS1271

We are using the ADS1271 and we have this strange situation, with the inputs shorted together, at around 80C the digital values shift by about 400 lsbs. Would this  be expected?

TIA

Yehuda

  • 0
    TI__Mastermind 20835 points
    Dear Yehuda,

    the shift in output codes over temperature is most likely due to offset drift of the device.
    The datasheet specifies a typ. offset drift of 1.8uV/°C. The histogram in Figure 19 in the datasheet shows that the drift is in the range of 1 to 5uV/°C.
    Assuming a drift of 2uV/°C would yield a shift in output codes at 80°C of 369 codes.

    LSB size: 2x VREF / 2^24 = 2x 2.5V / 2^24 = 0.298uV
    Offset drift: 2uV/°C x 55K = 110uV
    110uV / 0.298uV = 369 codes

    Regards,
  • 0 in reply to Joachim Wuerker
    TI__Mastermind 20835 points
    Dear Yehuda,

    I also want to mention that you will not see any effect of gain error when you do a test with shorted inputs. You need to input a signal >0V in order to see the effect of gain error drift.

    FYI: The drift of the reference voltage - which is usually larger than the gain drift of the device - will also show up as a gain drift.

    Regards,