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Original question:

TMP392: Start-up "Blip" of TMP392

TMP392: Mis-output during Startup

Allan Fan
Expert 7050 points
Part Number: TMP392

Hi expert,

My customer face a similar issue referring e2e post " Start-up "Blip" of TMP392" 

Customer already use 1% accuracy resistor 18.7k to set 70C threshold but has high chance to see the output drop at startup just at room temp.

In DS there is a reset delay time 10ms, does it somehow relates to the reset delay time and meet our expectation?  Any workaround to prevent the drop?   p.s. the drop doesn't drop every time but high chance

Does the low time relate to the Vdd cap? Cause we also see the output low time increased when we add 4.7uF. 

The concern is the output connect to a fuse. If there is any abnormal output from our temp switch, it might burn out the fuse. 

Thanks,

Allan

Thanks,

Allan

  • 0
    TI__Genius 11755 points

    Hi Allan,

    Thanks for providing the schematic, scope shot, and looking through the previous post. As Amit mentioned in that linked thread, this blip can occur when the resistors are not sampled correctly on power-up for the TMP392. I see in the schematic that the customer is using a single resistor for SETA and SETB, They should not do this, our team has found that using a single resistor for both SET inputs can cause resistor sampling errors. I suspect that this is the cause of the blip seen in this case. I would recommend to the customer to use a separate 18.7KOhm resistor for each SET input.

    Regards

    -Alex Thompson

  • 0 in reply to Alex Thompson
    TI__Expert 7050 points

    Hi Alex,

    Will we update the DS if we don't recommend to use single resistor connection for one channel?  

    Regards,

    Allan

  • 0 in reply to Allan Fan
    TI__Genius 11755 points

    Hi Allan,

    Thank you for catching this, if we can confirm that using 2 separate SET resistors resolves the customer's startup issue, then yes we will need to update DS. If you could please have them try to use 2 different resistors, and then reply on this thread with your findings, that would be greatly appreciated.

    Thanks

    -Alex Thompson