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TMP112EVM: The first TEMP< low limit not recognized

Nicole Han
Intellectual 2230 points
Part Number: TMP112EVM
Other Parts Discussed in Thread: TMP112, TMP390, TMP392

Hi, team, 

My customer is evaluating TMP112EVM for a new project. TM=1 for interrupt mode, only this bit of configuration register was set, other bits were using default value.

They found after connecting TMP112EVM to computer, If the temperature firstly dropped to below the low limit, there was no alert low given out. Then if temperature increased to above the high limit, there was alert low asserted. After that, if the temperature again dropped to below low limit, the alert can be asserted.

Why does the first TEMP < low limit after power on not recognized by the IC?

Actually not only customer, I also found this phenomenon on our EVM. 

  • 0
    TI__Intellectual 2230 points

    Add one more thing, If the temperature firstly increase to high limit for connecting, then there is alert. 

  • 0 in reply to Nicole Han
    TI__Genius 10040 points

    Hi Nicole,

    Thank you for posting to the Sensing forum.

    The ALERT pin functionality that the customer has seen is correct device behavior. The ALERT pin will first become active when the temperature reaches or exceeds the T(HIGH) threshold. After the pin is cleared it will only become active again when the temperature falls below T(LOW). Please refer below to Figure 16 from the device datasheet for an illustration of this:

    Additionally, section 7.5.4 of the datasheet goes into further detail about ALERT pin functionality for both Interrupt and Comparator mode.

    Best regards,

    Nicole

  • 0 in reply to Nicole Khoury
    TI__Intellectual 2230 points

    Hi， Nicole ,

    Thanks for replying. So the first low limit that met before the first high limit couldn't trigger the Alert pin. Every time after TMP112 powered on, it must experience a high limit activate, then it can report a low limit fault. Customer can accept it. It's not reasonable for most user case. 

    Is there a solution to this? Or do you have other parts to recommend? Thanks!

  • 0 in reply to Nicole Han
    TI__Genius 10040 points

    Hi Nicole,

    Unfortunately, I am not aware of a digital temperature sensor in our portfolio that has different alert pin functionality. 

    The TMP390 temperature switch has independent hot (30C to 124C) and cold (-50C to 25C) threshold detection, while the TMP392 switch has hot (30C to 124C) and warm (30C to 105C) threshold settings.

    Best regards,

    Nicole K