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TMP61: calculator with smaller polynomials, truncation of constants, calibration

Lenio Cacula
Genius 16230 points
Part Number: TMP61
  1. Does the TI Thermistor Design Tool allow the use of lower order polynomials?
  2. Does the TI Thermistor Design Tool provide expected min and max temperature error for the condition of using “nominal fixed values for polynomials”, Rbias resistor tolerance of either 1% or 0.5%, and no overall Gain and Offset final calibration (this would be done at final Functional Test if needed to be added)? We see min/max in the resistance tables but not sure if they are being utilized.

Thank you!

  • 0
    TI__Expert 6380 points

    Hi Lenio,

    Let me do my best to answer your questions.

    1. No the TI Thermistor design tool only supports the 4th order polynomial that's already in the document.

    2. No the TI Thermistor design tool does not provide the min/max temp error from Rbias resistor tolerance, but it could be calculated manually. On the tab titled "4th Order Polynomial TMP vs RES, use the polynomial where resistance is the independant variable (x) and Temp is the dependant variable (y). You can solve this equation for min and max resistance from the desired resistor tolerance to see how much temperature deviates due to changing resistance. Keep in mind that is only applies to a given temp, so it would need to be repeated for multiple temperatures.

    Regards

    -Alex Thompson

  • 0 in reply to Alex Thompson
    TI__Genius 16230 points

    With regard to error, the Thermistor Design Tool includes Device Resistance Tables with min and max. Can we use these to determine max and min sensed temperature error from typical resistance?

    Also, the sensitivity for voltage biasing circuit at 3V yield approx. 4.375 mv/°C. To increase sensitivity, is it possible to put two devices in series if you double Rbias and Vbias? Would this affect the individual Resistance vs temperature characteristic for this configuration?

    The customer questioned the note about AEC-Q200 qualifications. Why does the DYA package perform better than DEC and LPG packages in the terminal strength shear test?

    Thank you!

  • 0 in reply to Lenio Cacula
    TI__Mastermind 40945 points

    Yes, you can use the Min/Max from the Device Resistance Tables to estimate temperature error.

    No, the device was not intended to be used this way. The provided tables would not be applicable to this series condition. I can't recommend trying it.

    We have some people on vacation this week. It may take some time to research the answer to your shear question.

    thanks,

    ren