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TMP468: Thermal response time

ACGUY
Guru 11170 points
Part Number: TMP468
Other Parts Discussed in Thread: TMP103, LMT70, LMT01

Hi,

How much the thermal response time of TMP468 at local temperature at still air?

What is the local temperature sensor with the fastest response time at TI?

Regards,

ACGUY

  • 0
    TI__Expert 6715 points
    Hi ACGUY,

    Unfortunately, we do not have the thermal time constant of TMP468 in still air. We only have the response in oil as shown in the datasheet (tau<1sec).
    The thermal response will come down to the thermal mass. The smaller the mass the faster the response. In general, chip scale packages are smaller than other packages. I would recommend looking at TMP103, LMT70, and LMT01. What time constant are you looking for and what application is this for?

    -Kelvin
  • 0 in reply to Kelvin Le THS
    Guru 11170 points
    Hi Kelvin,

    Thank you for reply.
    I know that LMT70 response time (to 63-%) is 73-sec. Our customer requesting the more fast response time less than 30-sec for temperature sensor. I suggested thermo couple with precision ADC, However, my proposal was dismissed because it is expensive.
    They will calibrate products individually, so it does not matter the accuracy.
    Please let me know the temperature sensor with the fastest response time.

    Regards,
    ACGUY
  • 0 in reply to ACGUY
    TI__Expert 6715 points

    ACGUY,

    I need to double check with the team on the LMT70 time constant (it seems quite long for that package).

    Still air time constant:

    LMT01 (DFN) ~10 sec

    LMT8x family (SC70) ~10 sec

    I don't have still air data for TMP103 but I'm confident that it's much faster than LMT01 or LMT8x since it is much smaller package  However,

    it will depend if you're trying to measure board or ambient temperature.  If you're measuring board then TMP103 would be a good choice and since it's digital zero calibration is required for guaranteed accuracy.  If you're measuring air, you will need to thermally isolate the device from the board using pcb cut-outs.  

    The pcb may contribute to the thermal mass and slow the response of the device so layout is critical.

    Summary:

    For ambient measurement I would recommend the thru-hole LMT01 (LPG). This has a 20s thermal time constant.

    For board measurement I would recommend TMP103 (DSBGA).  I confident that it's one of the fastest SMD devices we have.

    If you can, go with digital and you don't have to calibrate for guaranteed specs. If you have to use analog instead, I would recommend LMT70 for SMD.

    -Kelvin