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AD8497:negative temperature & unipolar supply.

Hellow,

AD8495/AD8497: according to datasheet,

'Reference pin voltage can be offset to measure 0°C on single supplies.'

Question1:

Is this also applicable for negative temperatures,

i.e., is it possible to use unipolar positive power supply for negative temperatures measurements, if to add appropriate positive voltage to Reference pin?

For example, one should measure the temperatures in -50°C...+150°C

if +Vs=5V, -Vs=0,  Uref=1V,

would be Uout = -50°C * 5mV + 1000mV = 750mV?

If not, which minimal temperature is it possible to measure under unipolar supply due to Vref compensation?

Question2:

should one connect AD8497 negative input through 1M resistor to 0V,

if conditions are as in the example above?

Best regards,

bvn123

  • Hello bvn123,

    For question 1, your analysis is correct. The datasheet has a Measuring Negative Temperatures section on page 15. It just says that you can offset the reference (with a low impedance source) to measure negative temperatures on a single supply. 1V would work for this, as would 2.5V. Just as long as the desired temperature range is within the output range of the part.

    For question 2, either 1Meg to ground or 1Meg to the 1V reference would work. Look at figure 7 in the datasheet to see what the effect is. Your input common-mode voltage can be up to about 2.5V without running into any headroom limits. I would recommend connecting the negative input to 0V through the 1Meg resistor because the part is designed for that configuration and, chances are, it will be easier to rout on the printed circuit board.

    I hope this answers your questions.

    Best regards,

    Scott

  • Hello Scott,

    Thank You for Your answer and advice to use AD8497

    Best regards,

    bvn123