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LMT87-Q1: VOUT behavior when VDD=3V and temperature is -150C to 20C

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Replies: 11

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Part Number: LMT87-Q1

Hello,

 

Please advise VOUT behavior when VDD=3V and temperature is -150C to 20C.

Datasheet has following characteristics, so I believe VOUT accuracy is around +/- 6% and VOUT behave normal.

Could you guarantee that VOUT definitely increase when temperature decreased from 20C to -250C?

 


 

Best Regards.

  • Hi Toshio,

    -150C is beyond the specification of the device. We can't guaranteed behavior beyond what's in the datasheet since the condition is not tested.

    -Kelvin
  • In reply to Kelvin Le THS:

    Hello Kelvin-san,

     

    Thank you for your answer.

    I had a mistake in my question.

    I want to know output behavior while temperature is -50C to 20C.

     

    I want to confirm that output voltage will saturate like following red line but it will not reverse (decrease) like green line when temperature decreased to -50C.

     

    If you have or could simulate temperature and output voltage graph when VDD=3.0, could you provide me?

     


     

    Best Regards.

  • In reply to Toshio Ushikubo:

    Toshio-san,

    I believe the output will saturate similar to the red trace due to lack of headroom. Did you observe the output reserving at -50C?

    -Kelvin
  • In reply to Kelvin Le THS:

    Hello Kelvin-san,

     

    Thank you for your answer.

     

    I’m suggesting LMT87-Q1 and TLV3201-Q1 to perform temperature switch with large hysteresis (100C ON and 30C OFF) to customer.

    So I wanted to confirm that LMT87-Q1 output doesn’t behave like green line while low temperature.

    (Also I have not tested LMT87-Q1 at cold temperature.)

     


     

    Best Regards.

  • In reply to Toshio Ushikubo:

    Toshio-san,

    Please also consider an alternative solution with TMP75-Q1.  You can configure the ALERT pin to trigger in a similar manner using the comparator mode (TM).

    In comparator mode (TM = 0), the ALERT pin is activated when the temperature equals or exceeds the value in the T(HIGH) register and remains active until the temperature falls below the value in the T(LOW) register.

    Also, check out TMP102-q1.

    -Kelvin

  • In reply to Kelvin Le THS:

    Hello Kelvin-san,

    Thank you for your advice.

    Please answer following question for TMP75-Q1.
    Please answer if ALERT output is de-asserted in following case.
    (Please advise if ALERT behave as follows.)

    1) Set T_low and T_high after power up and ambient temperature is lower than T_high, and ALERT will de-asserted.
    2) Ambient temperature is higher than T_high and ALERT is asserted.
    TMP75-Q1 power is maintained, and temperature down to lower than T_high and higher than T_low, and re-set T_high, T_low and
    configuration register.
    ALERT output is de-asserted because temperature is between T_low and T_high.

    Best Regards.
  • In reply to Toshio Ushikubo:

    You will have to do a SW reset or power reset for case two to work. Reset T_H and T_L to the same values doesn't reset the device.
    From the datasheet:
    "The ALERT pin can also be cleared by resetting the device with the General-Call Reset command"

    -Kelvin
  • In reply to Kelvin Le THS:

    Hello Kelvin-san,

    Thank you for your answer.

    Your answer solved my question for TMP75-Q1.

    I recommended TMP75-Q1, but customer wants to close temperature switch function using LMT87 and comparator with processor is not concerned.
    So, could you answer for my question I posted on Jul 19 2017?

    Best Regards.
  • In reply to Toshio Ushikubo:

    Toshio-san,

    Please answer if ALERT output is de-asserted in following case.
    (Please advise if ALERT behave as follows.)

    1) Set T_low and T_high after power up and ambient temperature is lower than T_high, and ALERT will de-asserted.

    A: Alert will be de-asserted because Ta<T_high

    2) Ambient temperature is higher than T_high and ALERT is asserted.
    TMP75-Q1 power is maintained, and temperature down to lower than T_high and higher than T_low, and re-set T_high, T_low and
    configuration register.
    ALERT output is de-asserted because temperature is between T_low and T_high.

    A: ALERT will still be asserted because the device hasn't been reset (SW reset or power reset).

    -Kelvin
  • In reply to Kelvin Le THS:

    Hello Kelvin-san

     

    Thank you for your answer for TMP75-Q1.

     

    But I wanted you to answer following LMT87-Q1 question that I posted on Jul 19 2017.


     

    Best Regards.

     

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