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TCAN1146-Q1: CAN transceiver in fail state(INH pin on LOW)

Cornel Iuonas
Prodigy 10 points
Part Number: TCAN1146-Q1

I am using CAN Transceiver TCAN1146-Q1 with functionality of INH to control the power supply of the MCU.

INH pin is configured to be 300ms low when there is a WDG failure.

 I have a corner case where TCAN1146-Q1 enters in a state where INH is always low: I configure the WDG in window mode and on a diagnostic command I trigger WDG twice to force a reset. Right after I set the WDG in OFF mode.

 Even if TCAN1146-Q1 is in Fail state, INH pin should still be high.

 Could you please test this on your side and give a feedback why this is happening?

  • 0
    TI__Guru 53555 points

    Hi Cornel,

    Thanks for sharing you question on E2E. 

    How long does your watchdog test take? I would like to see if you may be encountering the sleep wake error (SWE) timer. This is a ~4 minute timer that will automatically put the transceiver into sleep mode (INH off) if it is not reset by the MCU or CAN communication (needs configuration). You can confirm if this is the reason for the device entering sleep mode by reading the status of the WKERR bit field in the INT_1 interrupt register. If this is the case, you may need to periodically clear the CANSLNT to reset this timer. Additionally, the device will time out into sleep mode from this timer if it remains in failsafe mode for ~4 minutes. The device should be returned to normal mode by the MCU before this time to avoid a timeout into sleep mode. 

    Please also ensure that pin 7 is configured for default INH behavior and has not been changed to another configuration in the DEVICE_CONFIG1 register.

    Let me know if this sounds like it may be the cause of the behavior you're seeing and if you have any additional questions on this device. 

    Regards, 
    Eric Schott  

  • 0 in reply to Eric Schott1
    Prodigy 10 points

    Hello Eric,

    This is nothing like it. The corner case is the following:

    WDG is in window mode, so triggering twice would give an WDG error and put INH line to low for 300ms.

    If I simulate a WDG error by triggering twice with 1millisecond delay. This should ensure that WDG has failed and put INH line to low for 300ms.

    Everything is fine so far. From the second(wrong trigger) until INH is pull to low there is a 2-5ms window.

    The issue comes if in this small window I send a command to CAN transceiver to disable the WDG. If I do this then CAN transceiver is dead. No CAN communication is waking it up, no external trigger. And MCU is not powered because INH is pulled LOW.

    The status registers I read periodically(each 10ms), INT registers are also cleared.

    Best Regards,

    Cornel