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LM20: LM20 operating temperature range

Tiger Tang
Prodigy 150 points
Part Number: LM20
Other Parts Discussed in Thread: TMP235

Hi team 

    My customer need used LM20 for temperature monitoring and OTP. And their over temperature pertection is 130C. Considering sensing error, actual temperature could be 132C or higher. But on datasheet, the maximum operating temperature of LM20 is 130C. So the question is if this operating temperature would cause reliability issue? 

   PS:  For exaple, the temperature is 132C, the reported temperature is 129C. System will continue working, but the temperature is over LM20 absolute operating temp. what's the effect on LM20. 

Thanks and Regards, 

Tiger 

  • 0
    TI__Expert 7855 points

    Tiger,

    The recommended operating temperature is based the actual free-air temperature (characterized using high precision instruments in an oil bath) and not the temperature reported by the device. If the device reports 129C but the ambient is actually 132C, this is technically out of the recommended operating condition. When operating outside of the recommended range, the device's operation can't be guaranteed (accuracy, reliability, etcs). TI can only guarantee performance within the specified operating conditions stated in the datasheet.

    What's the customer's application requirements (e.g accuracy, price range, analog/digital)? Have they considered TMP235 or LMT8x?

    We have a wide selection for digital sensors.


     
    -Kelvin

  • 0 in reply to Kelvin Le THS
    TI__Prodigy 150 points
    Hi Kelvin
    My customer Huawei have already used LM20 on their board. Can you tell me what's the risk if temp is over 130C a bit? Is the accuracy will become worse? Or device life will become shorter?
    Another question, is TMP235 p2p with LM20? Can we direct change to TMP235 if needed?
    Thanks!
    Regards
    Tiger Tang
  • 0 in reply to Tiger Tang
    TI__Expert 7855 points

    Tiger,

    When operating outside of the recommended range, the device's operation can't be guaranteed (accuracy, reliability, etcs). TI can only guarantee performance within the specified operating conditions stated in the datasheet. 

    Accuracy and reliability are at risk when operating outside of recommended operating range.

    If they are using the LM20 SC-70  package then they can switch to TMP235 SC-70.  TMP235 has a positive temperature slope so please compare the device characteristics from the datasheets to make sure if that's what the customer wants.

    -Kelvin

  • 0 in reply to Kelvin Le THS
    TI__Prodigy 150 points

    Hi Kelvin
    Thanks fro your recommend. I Have introduced TMP235 to them.
    But, this case was happen in a producted project. Customer want to know the risk of useing this device over 130C. Then OTP of their system is set to 130C and the signal is come from LM20B. This is used in a important system and can't be recalled. So know the risk is very important, could tell me what's the rish when use LM20B in this condition? And if there has failure risk, what could be the failure mode. Thanks!
    Tiger