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TPL5111: Timing watchdog

Patrick Corsar
Prodigy 10 points
Part Number: TPL5111
Other Parts Discussed in Thread: TPL5110, TPL5010

I have been looking for an IC like the TPL5111 (but opposite sort of) which acts like a timed watchdog to hard reset a MCU. Under normal operation the MCU will 'report in' by pulsing an input pin on the watchdog which resets the timer. If the MCU is stuck in an unknown state and does not 'report in' the watchdog timer will timeout and pull the MCU's reset pin low to reset the MCU. Best thing I can think of is a 555 timer with an AND gate on the output of the 555 timer. The trigger (MCU reporting it is fine) also resets the 555 timer and an AND gate with the inputs of trigger and 555's output rectifies the 555's starting condition of 0V. I know I have solved my own problem but is there anything that would serve this purpose which integrates both and consumes less power? 

  • 0
    TI__Genius 17811 points

    Hi Patrick, 
    The apps engineer supporting nano timers is out for today but should be in office tomorrow. 

    Regards, 

    Vicente 

  • 0 in reply to vicente flores prado
    Prodigy 10 points

    Hi Vicente,

    Thanks for the update.

    I think the TPL5110/1 does what I am after. Setting delay/M_DRV pin high resets the timer but confirmation that my understanding would be appreciated.

    Kind regards,

    Patrick 

  • +1
    TI__Intellectual 760 points

    Hi Patrick,

    Sorry for the delay in getting to your question. I am not certain I totally understand your question. Your understanding of the TPL5111's operation is correct. Using the 555 timer in a monostable mode could also work (using only the MCU pulse to reset the timer), I am just not certain why the AND gate would be necessary--using the AND gate to return the 555 to its starting voltage would imply that your 555 is in bistable mode, which does not really act like a timer, as much as a switch. My personal recommendation for an IC to use would be the TPL5010. It has the same functionality as the TPL5111 but it also features a WAKE output pulse at the end of each interval. It is a separate output from the RESET pin, which will be asserted low if the MCU does not 'report in'.