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TMP235: how to understand output non linearity

Noriyuki Takahashi
Genius 9850 points
Part Number: TMP235

Hi team

Customer would like to understand correctly the definition of output nonlinearity of TMP235.

1. Looking at the datasheet, output nonlinearity is +/-0.5C. Could you tell how to calculate this?

2. The note (1) about nonlinearity on P.5 seems to describe about the temperature accuracy, not about linearity. Is this understanding correct?

Regards,

Noriyuki Takahashi

  • 0
    TI__Mastermind 28070 points

    Hi Takahashi-San,

    1. This output non-linearity is only a typical spec for within a certain temperature range, but a ±0.5 °C non-linearity spec means that actual TMP235 linear output may diverge by as much as ±50mV (±0.5 °C * 10mv/°C) from the expected linear output. For simplicity I would say just look at the accuracy specification. 

    2. Correct, this footnote is more about accuracy, although the two are related. It is just referring to the fact that to get the accuracy specified in the datasheet, the piecewise linear function described in section 7.3 needs to be used, and not the ideal linear function, or any other method.

    Please let me know if you have any other questions. 

    Best Regards,
    Brandon Fisher

  • 0 in reply to Brandon Fisher94
    TI__Genius 9850 points
    Brandon,

    Thanks. Please let me confirm again.

    Regarding 1, is it correct understanding below to get Output nonlinearity?
    1. Measure the output voltage.
    2. Calculate temperature using the equation (2).
    3. Compare the temperature with very good accuracy temperature that is used as temperature reference.

    Customer would like to understand how to get output nonlinerrity in order to evaluate it by themselves.

    Regards,
    Noriyuki Takahashi
  • 0 in reply to Noriyuki Takahashi
    TI__Mastermind 28070 points
    Hello Takahashi-san,

    Yes that method will work. If they are looking to get the maximum non-linearity of a particular IC then they would really need to measure across temperature though, as the difference between the actual voltage and the results from the equation may change across temperature.

    Best Regards,
    Brandon Fisher
  • 0 in reply to Brandon Fisher94
    Prodigy 10 points

    Thank you very much.