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TMP708 not tripping

Ben Blumenthal
Prodigy 20 points
Other Parts Discussed in Thread: TMP708

hi,

I'm using the TMP708 in my design.

I have set the threshold to around 108oC with 9.53k resistor.

however, when I test the circuit with a heat-gun and thermocouple, the device trips at case temperature of 145oC.

what seems to be the problem...

thanks,

BenB>

  • 0
    TI__Mastermind 37750 points
    Hi BenB,

    Thank you for reaching out to us! There are a lot of unknown variables here. What is the distance from the device to your heat gun? Was the reference temperature placed right next to the TMP708? A typical temperature range of the heat gun is around 399°C to 427°C. Pointing the heat gun directly to the device without enclosed box is not ideally. There could be possibility that the thermometer thermal response is slower than TMP708 while a direct temperature >400°C. I would suggest that you need to put your board inside the chamber and sweep the oven from 106°C with 1°C increment.

    Hope this helps! Please let me know if you have any question.

    Aaron
  • 0 in reply to Aaron Heng
    Prodigy 20 points

    hi Aaron,

    thanks for your quick response. 

    I run a test with two fluke temperature sensor. one on my CPUs heatsink, and one on TMP708 with the enclosure closed. 

    they are in close proximity with one degree Celsius difference.

    they both go over the 108oC and the IC doesn't changes its output.

    today I changed the resistor to 15k and it seems to work at ~110oC

    thanks,

    BenB>