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TLIN1441-Q1: watchdog question

Chuqiang Wen
Expert 5825 points
Part Number: TLIN1441-Q1

Hi Expert,

Considering the functional safety requirement, customer have some questions when using TLIN1441-Q1 watchdog function. 

The background is that customer use the pin mode for watchdog and choose the 40ms twindow(WDT connect to GND). Due to some limitation, the MCU can only generate the 25ms or 30ms watchdog signal. 

  1. From the watchdog window timing diagram as above, the safe trigger area should 28±4ms, correct? 
  2. The minimum and maximum value of twindow are 32ms/48ms, the minimum and maximum value of twdout are 16/24ms. Does this range include the accuracy of internal oscillator(±10%)?
  3. Customer decide to set the 30ms for WDI input signal watchdog cycle time. Is there any risk need to considered? Can some ESD or EMI events will have some influence on the correct identification of watchdog feeding?

Thanks！

Regards,

Ethan Wen

  • 0
    TI__Guru 74252 points

    Ethan,

    If you look through this application note, your questions should be addressed. Please let me know if you still have questions after looking through the application note.

    Regards,

    Eric Hackett 

  • 0 in reply to Eric Hackett
    TI__Expert 5825 points

    Hi Eric,

    Thanks for your support. 

    But I can not find the answer through this app note. 

    Could you please help me understand these questions? 

    1. From the watchdog window timing diagram as above, the safe trigger area should 28±4ms, correct? 
    2. The minimum and maximum value of twindow are 32ms/48ms, the minimum and maximum value of twdout are 16/24ms. Does this range include the accuracy of internal oscillator(±10%)?
    3. Customer decide to set the 30ms for WDI input signal watchdog cycle time. Is there any risk need to considered? Can some ESD or EMI events will have some influence on the correct identification of watchdog feeding?

    Regards,

    Ethan Wen

  • 0 in reply to Chuqiang Wen
    TI__Guru 74252 points

    Chuqiang,

    1. The safe zone will be 24-32 ms in the window configuration, so yes, 28+/-4ms.

    2. Yes, it does.

    3. Either event could interfere by distorting the watchdog service signal, but if it interferes with your watchdog servicing, it will likely interfere with other parts of the system as well. Proper layout and protection components on the LIN bus will help mitigate this.

    Regards,

    Eric Hackett 

  • 0 in reply to Eric Hackett
    Prodigy 70 points

    Dear Eric,

    Could you please tell me if the watch dog timer will restart at every time I refresh the watch dog by giving an edge to WDI? And if not, how could I stop the watch dog timer in PIN mode.

    Best regards,

    Ying

  • 0 in reply to ying li
    TI__Guru 74252 points

    Ying,

    Yes, when the watchdog is serviced, the timer immediately restarts, and you must service the watchdog from that point. This is true for both window and timeout watchdog functions.

    Regards,

    Eric Hackett 

  • 0
    Prodigy 10 points

    Hi Eric 

    Could you help me double check :During the initialization process, we do not feed the watchdog of 1441,will 1441 reset our MCU? if not ,our strategy will be that  not feed the first watchdog until out initialization is completed .....thanks

    Gavin huang

  • 0 in reply to Huang Shenggang
    TI__Guru 74252 points

    Gavin,

    The watchdog on TLIN1441-Q1 does not start until it receives the first service pulse. You can take as long as you need to configure and then service the watchdog once you're ready.

    Regards,

    Eric Hackett