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TCAN1146-Q1: CAN Bus fault

Che Wen Yeh
Expert 1070 points
Part Number: TCAN1146-Q1


Hi Teams,

We have some questions about TCAN1146-Q1 bus fault as following, please help to check, thanks.

1.In our architecture, as shown in the diagram, but there is no device 1. Can the open bus fault detection in device 2/3 still function?

image.png

2. When an open CAN bus fault occurs, is it possible to meet the following recovery time? 

3. Will the TCAN1146 force the CAN bus into bus-off state upon a CAN frame error or only bus Fault Interrupt?

  • +1
    TI__Mastermind 30340 points

    Hi Che,

    1. Yes

    2. There is no issue on the transceiver side, however, as CAN open circuit can cause error frames, we've seen some customer's MCU will stop communication due to receiving too many error frames. So this is more likely a software related question.

    3. No, such kind of fault will not force the transceiver into bus off state, it will only issue an interrupt. It's the MCU decided if it should enter bus off state.

    Regards,

    Sean

  • 0 in reply to Sean Guo
    Expert 1070 points

    Hi Sean,

    For question2,

    The current issue is that the recovery is too fast (Criteria within 200ms+/-20ms). How should we adjust the SW? Thanks.

  • +1 in reply to Che Wen Yeh
    TI__Mastermind 30340 points

    Hi Che,

    The transceiver doesn't care how fast it takes to recover. As soon as the open fault is fixed it will be able to transmit normally.

    Regards,

    Sean

  • 0 in reply to Sean Guo
    Expert 1070 points

    Hi Sean,

    In the following architecture(No device 1), if either device 2 or 3 experiences an open-bus fault, can both sides(2/3) detect it? Thanks.

    image.png

  • 0 in reply to Che Wen Yeh
    Expert 1070 points

    Hi Sean,

    Could you help to check this question? thanks.

  • +1 in reply to Che Wen Yeh
    TI__Mastermind 30340 points

    Hi Che,

    Yes, either device 2 or 3 has an open fault, both transceivers will detect it.

    Regards.

    Sean

  • 0 in reply to Sean Guo
    Prodigy 30 points

    Hello Sean,

    Here I also with a similar CAN fault case need to ask that.

    In that bus only with two ECU on topology. And all termination resistors are bulied in the ECU, not external independence.(Internal using split termination.)

    If CAN_H(or CAN_L) line open, that bus fault can be detection?(show in below photo.)
    And what bus fault FLAG will be rising?(like "CANBUSTERMOPEN" or "CANBUSOPEN"?)
    Or that is need using other way to dectation that?
    Because that fault is similar three(or more) device topology's Fault 1 mixed Fault 3(and 4).

    Can you help to check what missing for us?

    Thansk~

    BR,

    Nikoals

  • 0 in reply to Nikolas Guo
    TI__Mastermind 30340 points

    Hi Nikolas,

    In this case, all the transceivers can detect CANBUSTERMOPEN, since there is still half termination on the node.

    Regards,

    Sean

  • 0 in reply to Sean Guo
    Prodigy 30 points

    Hello Sean,

    Our firmware and test team response in that case(two device on bus, one line of bus dis-connect), they can't get CANBUSTERMOPEN(other case can succeed getting fault flag). And they still can get ACK. So, They also couldn't over that flag to turn off bus.

    We speculate the reason is from that is still connected line(CAN H or CAN L) let Tx(or Rx) still working send signal to MCU?

    Can you provide any ideal for us?

    Thanks~

    BR,

    Nikolas 

  • 0 in reply to Nikolas Guo
    TI__Mastermind 30340 points

    Nikolas,

    If there is still half termination on the bus, disconnecting one line may still able to communicate in this case. Those interrupt work by measuring the differential output on the bus. There are certain ranges to determine if it's a termination open, or bus open (no termination). Because one CAN line can still work normally, the CAN driver is able to drive dominant states within the acceptable range so it's not trigger the bus open interrupt.

    That being said, CAN is very robust, so in a simple network with only two terminating nodes on the bus, you may not see error frames with one of the CAN signal disconnected, especially if the data rate is not very high. In a more complex network (i,e a third node on the bus as datasheet shown), it should be able to detect the CAN open fault if one line lost.

    Regards,

    Sean