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Internal temperature sensor of TMS320F28027

Ashutosh Pailwan1
Expert 2480 points


I am using internal temperature sensor for tmperature measurement

I am using control suite example of adc_temp_seso_conv 

It measures temperature and converts to degree

I had executed the sample code

1. I am seeing 47 degrees as tmperature in watch window of CCS and it is fluctuating However, the ambient air temperature is 32 degree.

2. If I am using internal oscillator with temperature compensation . How reliable it is compared to external oscillator which has variation of 50ppm i.e 0.0005% variation.

3. Also internal oscillator has variation of +- 0.1 MHZ for variation of +-10 degree. SO I was proposing to use temperature compensation , While it is showing 47 degeree for ambinet of 32 degree. 

  • 0
    Guru 192875 points
    Hi Ashutosh,

    Its an internal temperature sensor hence it will indicate the junction temperature of the device and not ambient temperature.
    Please go through the section 1.12 on Internal Temperature Sensor in Adc and Comparator user guide.

    Regards,
    Gautam
  • 0 in reply to Gautam Iyer
    TI__Guru 60865 points
    Hi Ashutosh,

    The absolute accuracy of the temperature sensor is typically in the ballpark of +/-15 deg. C. As Gautam mentioned, this is device junction temperature, not ambient temperature.

    Using temperature compensation on the oscillator, the frequency accuracy will be typically +/-0.5%, worst case +/-1% (this doesn't drift linearly over temperature, but instead is somewhat of a sawtooth as the procedure changes the trim to compensate for the temperature variation). An external XTAL will typically have much tighter frequency accuracy than this - you will have to do the math on your particular XTAL using both the initial ppm error + ppm error over the intended operating temperature range.

    Note that the temperature compensation function doesn't ever turn temperature sensor readings into absolute temperature, so the (rather large) temperature error doesn't affect the effectiveness of the oscillator compensation procedure.