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TMP468: Calibration to get accurate data in EVM evaluation

Takashi Onawa
Genius 13200 points
Part Number: TMP468

Hi Team,

Are All individual channel calibrations necessary to get accurate measurement result in EVM evaluation?

How much data variations should be observed under default setting, N-Factor : 1.008 and offset : 0.
I saw a little bit big measurement error(Around greater than 1C) on EVM evaluation though.

Regards,

Takashi Onawa

  • 0
    TI__Expert 6820 points

    Hi Takashi,

    Since each channel is connected to a different MMBT3904LP transistor there may be a small variance between channels. What is your set up and test method?

    Regards,
    David

  • 0
    TI__Mastermind 43715 points

    Hello Takashi-san,

    It is normal for different transistor models (and manufacturers) to have variations in N which can account for 1C error or more. The transistors on the TMP468EVM were chosen for their small size. It was found that their N is close to 1.000. By default, TMP468 and other sensors on the market expect N=1.008. The following formula predicts temperature error due to N-Factor error. It shows that these transistors on the TMP468EVM will have about -2.3C temperature error at room temperature if the N-Factor is not configured correctly for N=1. Try setting N=1 for each channel in the EVM, and you should see the output align with reported local temperature.

    Thanks,

    Ren