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ADS1258-EP: Reading Device Temperature

David Fernie
Prodigy 30 points
Part Number: ADS1258-EP

Hello,

Currently we are able to retrieve channel data from the ADS1258-EP without any issue, including from internal channels such as the reference reading. However, we are unable to obtain correct temperature data.

For example, we get 270155 as a sample with a reference of 4.765V, and following the data sheet, we calculate:

(((270155 * 4.765V / 2^23b)*1e6 uV/V - 168000uV) / 394) + 25 = -11.91°C

We know that the IC is at approximately 23°C. Are we doing something wrong?

Thanks,

David

270155
  • 0
    TI__Mastermind 34971 points

    Hi David,

    Using a 4.765V reference, your full scale range (FSR) is 2*1.0666*4.765, or 10.165 V.

    If you take the FSR and divide by the # of codes (2^24), then you get an LSB size of 0.6059 uV.

    If you multiply the LSB size by your code value (270155) you get 163,687. This gives you the temp reading in uV, which you can then plug into equation 10 in the ADS1258-EP datasheet.

    163687 - 168000 = -4313

    -4313 / 563 = -7.66

    -7.66 + 25 = 17.34°C

    Please note that the temperature sensor on the ADS1258-EP is not high precision and can be 5-10°C off from the true value. The temp sensor is intended as a coarse measurement to determine if the ADC is getting closer to its maximum operating temperature.

    -Bryan