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TMP100: Large TMP100 readout fluctuations in vacuum

Petr Suchanek
Prodigy 30 points
Part Number: TMP100
Other Parts Discussed in Thread: TMP461-SP, TMP112

Dear all,

I have a question regarding TMP100NA/3K in vacuum. During normal room temperature the output read-out has only -1 LSB fluctuations. But in vacuum, 10^-5 Pa, we measured what is described below (hexadecimal values):
frame 0: Temp: 0x0B02
frame 6: Temp: 0x0AD0
frame 10: Temp: 0x0BD7
frame 13: Temp: 0x0AD7
frame 16: Temp: 0x0B15
frame 20: Temp: 0x0B3B
frame 23: Temp: 0x0B8C
frame 27: Temp: 0x0B22
frame 30: Temp: 0x0B02
frame 34: Temp: 0x0B2E
frame 37: Temp: 0x0B47
frame 41: Temp: 0x0A6C

Would you have any explanation what could be behind this large fluctuations?

Best regards, Petr Suchanek

  • 0
    TI__Mastermind 43715 points
    Hi Petr,

    It's normal for package stress to alter performance of an analog IC. It would be interesting to see if you could vary the pressure and record a proportional change in temperature. Do you have another temperature reference in your chamber to ensure this is not the actual temperature varying? The range is only 1.4C.

    I don't believe we can guarantee device operation under this condition. You might want to consider TMP461-SP instead. It comes in a ceramic package which will have less package stress. It's currently our only temperature sensor which is Radiation Hardness Assured for space applications.

    Thanks,
    Ren
  • 0 in reply to Ren Schackmann
    Prodigy 30 points

    Hi Ren,

    thank you for your the clarification. We did not have another sensor as a reference, but have the same measurements from non-vacuum environment. Those were completely smooth. For next designs, true, we have also seen TMP461-SP or TMP112, but this one doesn't come in the ceramic package.

    Regarding the fluctuation range, in other measurements we had the fluctuations even up to 12 degree C, if the whole peak-peak range is considered, see the image.

    Regards, Petr

  • 0 in reply to Petr Suchanek
    TI__Mastermind 43715 points
    Hi Peter,

    These fluctuations are not expected, but I'm not sure we will be able to help you debug. We cannot reproduce your vacuum testing. If you suspect that you're having communications issues, please post oscilloscope shots of the bus.

    Please let me know if you have further questions, but I'll consider this topic closed for now.

    Thanks,
    Ren
  • 0 in reply to Ren Schackmann
    Prodigy 30 points

    Hello Ren, when we are measuring next time, we can try to check the communication lines, too, or add another temperature sensor as a reference. Till then, yes, let's close this topic.

    Thanks.

    Regards, Petr