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TMS320F28377S: f28377s internal temperature sensor accuracy

Joe Zhu
Intellectual 2540 points

Part Number: TMS320F28377S

Hi Champion,

I find in datasheet that F28377S internal temperature sensor accuracy in datasheet is 15 deg, but in example:

if(DevCfgRegs.REVID >= 3)
{
//
//for production devices (Rev. C), pull the slope and offset from OTP
//
tempSensor_tempSlope = (int32)getTempSlope();
tempSensor_tempOffset = getTempOffset();
}
else
{
//
//for pre-production devices, use these static values for slope
//and offset
//
tempSensor_tempSlope = 5196;
tempSensor_tempOffset = 1788;
}

Seems we have calibration data in OTP, so what is the accuracy after calibrate? Do we have other way to make it more accuracy?

Thanks!

BR

Joe

  • 0
    TI__Guru 60865 points
    Hi Joe,

    The +/-15 deg. C specification is when using the calibration data in OTP. To get better accuracy, the customer will have to provide their own temperature calibration or temperature reference points.
  • 0 in reply to Devin Cottier
    TI__Intellectual 2540 points
    Hi Devin,

    So if customer can measure case temperature, do we have a formula to calculate the temperatur, because F28377S max temperatur in datasheet mark is TJ, so customer should comfirm TJ not over limit.

    Thanks!

    BR
    Joe
  • 0 in reply to Devin Cottier
    TI__Intellectual 2540 points
    Hi Devin,

    Do you have any idea about that? The reason is we cannot qualify ambient temperature, just junction temperature in datasheet, so customer should keep junction in area.

    Thanks!
    BR
    Joe
  • 0 in reply to Joe Zhu
    TI__Guru 60865 points

    Hi Joe,

    Yes, it should be possible to estimate the junction temperature based on the ambient temperature and some other conditions.  You can find the section that gives the device thermal characteristics in the datasheet section "5.7 Thermal Resistance Characteristics".  

    If the customer wants a thermal alarm, probably they would want to test their system in production at the max rated power and temperature.  They can then capture an internal temp sensor reading at this temperature and store it in customer OTP.  If, during deployed operation they detect a temp sensor reading at the captured value, they could initiate a soft shutdown or warning as appropriate for the system.  If the reading greatly exceeds the captured value, they could potentially do an emergency shutdown.

  • 0 in reply to Devin Cottier
    TI__Intellectual 2540 points
    Hi Devin,

    So what is the best case if customer tuning slope and offset themselfves, because even if it is a sensor, it has its limit.

    Thanks!

    BR
    Joe
  • 0 in reply to Joe Zhu
    TI__Guru 60865 points
    Hi Joe,

    Based on characterization, the sensor is linear to within at least +/-1 deg. C across the normal operating range. Note that the customer will also experience additional errors in the calibration due to their calibration forcing/sensing accuracy and the F2837x ADC.