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TCAN1043G-Q1: CAN Transciver electrical characteristics --- nFAULT abnormal output

Hsin Bruce
Prodigy 130 points
Part Number: TCAN1043G-Q1
Other Parts Discussed in Thread: TCAN1043

Tool/software:

Hi TI member,

We have a CAN test problem need your help.

As below is our schematic connection of CAN tranceiver. 

We encountered an issue with the CAN transceiver — an abnormal output on the nFAULT pin.

As shown in Figure 1, our CAN architecture has one shared output (U299 & U300). When testing packet transmission between the two CANs, U299 continuously outputs nFAULT (see Figure 3), though there is no packet drop or error in CAN transmission, and the other side (U300) does not output nFAULT. We can't confirm what kind of anomaly this is (refer to the datasheet, maybe TXDDTO/TXDRXD).

We conducted the following tests for this issue:

1. Swapping U299 with the standalone U523 on the right side, neither CAN exhibited abnormal output on the nFAULT pin.
2. Moving U299 to U300's position. then U299 will keep the nFAULT pin abnormal output.

Based on these tests, we believe the issue may be related to the electrical characteristics of the CAN transceiver, as there seems to be a compatibility issue. U299 exhibits this issue in the shared circuit but does not when moved to another position, whereas U300 and U523 show no issues in either position.

This issue has appeared in 5 out of 1,500 DUTs. We would appreciate your assistance in confirming if similar issues have occurred before or if you have any recommended directions for analysis.

Thank you.

Fig1: U299 & U300 connection

 

Fig2: V31C/V31U CAN Failure

Fig3: nFAULT continue output

  • 0
    TI__Expert 6600 points

    Hi TI Expert, 

    FYI, U299/U300/U523 are all TCAN1043GDRQ1.

    May We have your comment accordingly?

    Thank you.

  • 0 in reply to Evan Wang
    TI__Guru 69972 points

    Evan,

    We can discuss this through email, and I will post the results in our internal forum.

    Regards,

    Eric Hackett 

  • 0 in reply to Eric Hackett
    Prodigy 130 points

    Hi Eric,

    Is there any update regarding the abnormal behavior of the TCAN1043G FAULT pin?

     Additional question,

    We would like to inquire if TI has conducted any compatibility tests for CAN transceiver. Specifically, have there been tests to ensure consistent connectivity and transmission with CAN transceivers from different manufacturers?

    Thanks,

    Bruce Hsin

  • 0 in reply to Hsin Bruce
    TI__Guru 69972 points

    Bruce,

    I'm working on this issue through email, I have responded and asked more questions for the customer.

    To answer you question, no, this feature was only tested with TI CAN transceivers, and the current measurement circuit for fault detection is susceptible to impedance differences between transceivers which can skew the current reading. In some cases this results in false fault reporting on the nFAULT pin.

    Regards,

    Eric Hackett 

  • 0 in reply to Eric Hackett
    Prodigy 130 points

    Hi Eric,

    Thanks for your reply.

    You suggestion is “the current measurement circuit for fault detection is susceptible to impedance differences between transceivers which can skew the current reading.”
    According our test, the same problem only happens on one transceiver, another one is no problem. Swap the position also follow transceiver.
    If it is cause by different termination resister. We deliberately adjust the termination to a wrong value, can see a similar phenomenon on all TCAN1043?

    Thanks,

    Bruce Hsin