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TCAN1042-Q1: Bus fault detection with 8-pin CAN transceiver like TCAN1042-Q1

Atsushi Hirai
Expert 4980 points
Part Number: TCAN1042-Q1
Other Parts Discussed in Thread: SN65HVD257, TCAN1043, TCAN1043-Q1

Hi TRX team,

My customer is looking for a solution to detect a CAN Bus fault (for example CANH/L shorted to VSUP, VCC or GND, or open) with 8pin CAN transceiver and some external circuit and/or MCU.

Have you ever heard any good solution for this requirement? Please give me your advice.

Regards,

  • 0
    TI__Intellectual 2090 points

    Hi Atsushi,

    CAN bus fault detection is limited for 8-pin CAN transceivers.  Most applications today are implementing I/O voltage shifting for the extra pin feature.  The SN65HVD257 device is a 5V CAN transceiver with a FAULT output.  This FAULT pin will trigger only on TXD DTO, RXD DTO, under-voltage, or over-temperature conditions, though.  That means that if the CAN bus is stuck dominant, that the device will be able to report a fault.  Or if there is a persisting high-current condition caused by a bus fault, the persistent current could heat up the device enough to communicate an over-temperature event.  As I said, though, the bus fault detection is limited for 8-pin CAN solutions.  Our TCAN1043 possesses bus fault detection reporting, but it is a 14-pin CAN transceiver.

    Would the customer be willing to investigate the SN65HVD257 or the TCAN1043 devices for their application needs?

    Best Regards,

    Max Megee

    TI Transceiver Applications

  • 0 in reply to Max Megee
    TI__Expert 4980 points
    Max-san,

    Thank you for your suggestion. But my customer needs AEC-Q100 qualified device.
    BTW, Have you seen a fault detection circuit by external device and components ever before?

    Best Regards,
  • 0 in reply to Atsushi Hirai
    TI__Intellectual 2090 points
    Atsushi-san,

    It may be that the TCAN1043-Q1 is the only device that we can recommend for this application then.

    As far as an external solution for CAN bus fault detection, the implemented scheme will likely be much more complex than the customer desires. The solution would have to include a couple of differential amplifiers to measure and evaluate differences in bus current between the CANH and CANL lines. The solution should only be operating during dominant bits on the bus, so some kind of logic detection would also be required. All of the added components must not hinder the bus communication or add significantly to the series resistance on the bus. And all of the logic and current detection would likely require a control scheme of some kind.
    In summary, it would be much easier to move to a 14-pin CAN device with integrated bus fault detection than it would be to add all of the needed complexity for an external solution. Multiple external components would be required, and I am unaware of a proven external solution on the market today. My fear would be that the customer would enter into a long and laborious debug cycle if they chose that route for their design.

    Does that make sense? Is there a particular reason why the customer is limited to an 8-pin transceiver? Is there a specific situation in their application space for which they require bus fault detection?

    Best Regards,
    Max
  • 0 in reply to Max Megee
    TI__Expert 4980 points
    Max-san,

    Thank you for your advice.
    Customer understand your suggestion. I close this thread.

    Thanks,