• Resolved

TMP411: The THERM pin (pin4) keeps high at -25 degree C - is it right?

Part Number: TMP411

Hi team,

My customer is using TMP411 and wants to know the THERM pin (pin 4) logic.

Test condition: -40 degree C, and TMP411 is used to enable the whole system. I want to double check the status of THERM pin at power on. is default setting for the THERM range 0~85C, or just below 85C?

customer found the system start up normally at -40C. could you please double confirm whether there's low temp limit at power up of the THERM pin?



  • All of the following assumes default settings at power-on:
    1. The ALERT/THERM2 pin is configured as an ALERT which will assert an interrupt if the low or high limits are exceeded.
    2. The high limits and THERM limits are 85C. The low limits are 0C.
    3. The Consecutive Alert register is set to 2. This means ALERT will not assert until a limit is exceeded for two consecutive temperature measurements. This feature does not affect THERM (or THERM2) operation.
    4. The THERM pin will assert if the the THERM limit is exceeded. There is no lower limit for THERM (or THERM2.)
    5. The Shutdown (SD bit) is not set, so the device will take temperature measurements automatically.
    6. The Conversion Rate is set to 0x80, which means the device will take temperature measurements as fast as it can.
    7. The device takes 115ms to complete one temperature measurement for each channel (page 5 "Conversion Time.") The local and remote temperatures count as one channel each. The Conversion Time is fixed and cannot be changed.

    The customer's issue could be that they are using THERM pin instead of ALERT/THERM2 pin. It is not possible to assert a THERM event due to temperature being too low.

    The customer's issue could be that they are not waiting long enough after power-on. Due to power-on-reset setting of SD bit, the device will begin a temperature measurement as soon as it is able to at power-on. Due to Consecutive Alert setting, the device will not assert ALERT until two temperature measurements have been made. This means it would take at least 345-460ms (depending on which channel) to assert an ALERT at power-on.

  • Mike,

    The default startup THERM limit 0x55 (85C in standard temperature mode and 21°C in extended
    temperature mode, pg 25 of datasheet).

    Table 3 Register Map Summary also has the default value information for various registers.

    Is the customer experiencing problems?


  • In reply to Kelvin Le THS:

    Hi Kelvin,

    thanks for response. Customer's question is whether there's any low temperature limit for the THERM pin?

    for ALERT or THERM2, there're both high and low limit. How about the THERM?



  • In reply to Ren Schackmann:

    Thanks Ren.
    one more question:
    customer are looking for temp sensor whose default Therm limit is beyond 100 degree C. Do we have this kind of device? their system needs to be able to startup in 100C.

  • In reply to Mike Wang2:

    The limit register is programmable and could be set to 100C by the customer.

    Our temperature switches offer a wide variety of preset temperatures limits.
    1. TMP302C and TMP302D are pin configured and can be set up to 125C in 5C increments. These devices do not offer an under-temperature alert.
    2. TMP303D offers both over-temp and under-temp alert, but these are fixed at 125C, and -15C non-configurable.

    It's possible for us to create variations of TMP302/TMP303 for high volume customers. You would have to contact the product line through the sales channels.

  • In reply to Ren Schackmann:

    Hi Ren,

    I know the TMP411 can be programmable. However, at power on, the limit registers would be POR default value, which is 85C. So if the system power up at 100C, the TMP411 would generate THERM to prevent system from powering on.
    So it seems the only solution we have is TMP30X.

    By the way, I checked the Q grade device - TMP411DQDGKRQ1. the POR value of the THERM LIMIT REGISTER is 6E, which refer to 110C. Does it also meet this requirement?

  • In reply to Mike Wang2:

    Yes, TMP411DQDGKRQ1 is the only variant to have this increased high limit at power-on reset.