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MSPM0G1506: Internal thermometer results are not output correctly

mori.oq
Prodigy 140 points
Part Number: MSPM0G1506
Other Parts Discussed in Thread: SYSCONFIG

Hello. My name is Mori.

I checked the internal thermometer, but it didn't give me the expected results.
I checked when the outside temperature was 23.3℃, but the result was 4℃.
TEMP_SENSE0.DATA was set as 749 and the AD value was output as 1907. (Vref is 1.4v)
The AD value will be about 100 counts higher than expected.

• TSc = -1.8 mV/C
• TEMP_SENSE0.DATA = 749
• TSTRIM = 30℃
• ADCCODE = 1907

VSAMPLE(mv): 1907 * 1400 / 4096 ≒ 651
VTRIM(mv): 749 * 3300 / 4096 ≒ 603
TSAMPLE: (1/-1.8) * (651 - 603) + 30 ≒ 4

I have attached an image of the SysConfig settings.
Please let me know if there is anything wrong.

  • +1
    TI__Mastermind 25570 points

    Hi Mori,

    The Temperature Sensor Calibration factor uses reference of 3.3V and the trim temperature was taken at 25 C.

    //Formula found in TRM Section 2.2.5
#define TEMP_TS_TRIM_C                                            ((uint32_t)25)
/*
 * Constant below is (1/TSc). Where TSc is Temperature Sensor coefficient
 * available in the device datasheet
 */
#define TEMP_TS_COEF_mV_C                                             (-571.42f)

//Gets the voltage for the trim temp, this is done at 25 C
float VTrim = 3.3/4096 * (DL_SYSCTL_getTempCalibrationConstant() -0.5);

//Gets the voltage for the sample from the ADC
float Vsample = 3.3/4096 * (adcResult - 0.5);

//Takes the voltage from trim and ADC to get temperature in C
float gTemperatureDegC = (1/TEMP_TS_COEF_mV_C * 1000) * (Vsample - VTrim) + TEMP_TS_TRIM_C;

//converts C to F
float gTemperatureDegF = 9.0/5.0 * gTemperatureDegC + 32;

    I notice the discrepancy between the code and what the datasheet says for the Temperature sensor coefficient, so let me look into that for you.

    Regards,

    Luke

  • +1 in reply to Luke Ledbetter
    Prodigy 140 points

    Hi Luke

    Thank you for your reply.
    I understand that the datasheet and code are different.
    Thank you for your investigation.

    ・TSc = -571.42mV/C
    ・TSTRIM = 25℃

    I tried to check the operation, but the output was 24.9℃ compared to the outside temperature = 23.4℃.
    It's almost the same as TSTRIM, but
    Proceed with this setting for now.

    Thank you for your response.