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DAC38J84: temp sensor

Asaf Samira
Prodigy 180 points
Part Number: DAC38J84


Hi,

I am using DAC38J84 component in my design.

I have checked two different cards with a thermal camera and compared the case temp. to the internal temp. sensor.

The case temperature of the DAC was the same (in both cards) but there was a different of almost 10 degrees in the DAC temperature sensor

FIRST CARD:

DAC_TEMP_SENSOR = 75 DEGREES

SECOND CARD:

DAC_TEMP_SENSOR = 84 DEGREES

Please advise What could be the reason for the difference?

  • 0
    TI__Mastermind 40960 points

    Hi Asaf,

    Are the two devices on the same board? Or are the two devices on totally different boards?

    in either case, do you have another board that you can try?

    The Temp sensor is factory trimmed, so you should see roughly the same number if you are confident the case temp is the same.

    Thanks,

    Rob

  • 0 in reply to Rob Reeder
    Prodigy 180 points

    Hi,

    The two devices on different boards.

    I have checked two more boards (4 boards in total).

    results is as below:

    • 2 boards - the DAC_TEMP_SENSOR showed 84 degrees
    • 2 boards - the DAC_TEMP_SENSOR showed 75 degrees

    The thermal picture of all 4 boards were the same

    the only different was in the DAC internal temp. sensor

  • 0 in reply to Asaf Samira
    TI__Mastermind 40960 points

    Hi Asaf,

    Thanks for the additional information?

    Even though the sensor is trimmed, this is a relative measurement and has its own linear regression.

    Keep in mind, we don't guarantee the temperature sensor in the specification tables.

    Also, is the spi interface to the DAC running at a 1MHz or more?

    If so, this might be an issue in getting repeatable data. Try slowing down this interface.

    See section 7.3.23 on page 54.

    Regards,

    Rob