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SN65HVD230: CANH and CANL short circuit and IC Failure

Part Number: SN65HVD230

Hi,

We have used CAN SN65HVD230 in our Vehicle Tracking Device board. Testing is done in Lab, using a CAN to USB convertor and a PC. Worked fine. We are facing lot of failures of CAN IC in multiple vehicles which

consist of multiple nodes.

Note: We are using shielded two core cable for CAN but unfortunately we have connected shield with CANL cable in the wiring harness and that shield is not connected to body or ground. Since shield is isolated with

ground it worked fine here but I believe this may be one of the reason for failure. Will that affect CAN IC in anyway like EMI/EMC or differential cable requirement is not met here?

Please review my schematic and suggest any improvement to be done .

Spec: 500kbps speed communication. EV Vehicle.

Common mode choke filter : SRF2012-121YA

  • Saravanan,

    Typically the shield is connected to the chassis or GND like you said. Connecting it to CANL seems like it may negate the effect of the shield in the first place. Can you explain the failures a bit more, as in what kind of failure you are seeing? 

    Regards,

    Eric Hackett 

  • Multiple scenario is happening like only CANH is shorted with GND, CANH and CANL both is getting short with GND and in some cases both CANH CANL is not short circuited with GND but CAN function is not working at that point when I replace with new transceiver it is working fine. Also check if my schematic is ok or not. Does this transceiver SN65HVD230 is automotive compliant if not can you suggest with one.

    Thanks for your response.

  • Hi Saravanan,

    No, SN65HVD230 is not automotive qualified. Only 5V supplied CAN transceivers are currently used in automotive applications that require compliance with the ISO 11898-2 CAN standard. A similar 5V device to this would be the TCAN1044A. 

    The schematic looks good overall. I would recommend against including series resistances on the CAN bus lines as CAN is relatively sensitive to series voltage drops. If bus fault current limiting is required, I would recommend looking at transceivers with higher bus fault tolerance (TCAN1044A will help with this) or include active protection such as a PTC fuse that will be low-ohmic in the nominal case. 

    It is not too surprising to me that the configuration where CANL is connected to the cable shield is causing issues here. Th shield conductor is not designed to carry signal and it is not suitable for a differential signal pair to travel on non-like conductors. Furthermore, the shield wire is likely being exposed to a harsh electrical environment (as is it's purpose) and thus presenting high energies to the transceiver pin that may cause damage. This connection should be fixed so that the internal protected cables are used for both CANH and CANL and the shield conductor is properly left to protect these signals from electromagnetic interference. 

    Regards,
    Eric Schott

  • According to your suggestions I will replace TCAN1044A and provide shield separately. I will let you know if these changes resolve my problem.

    Regards,

    Saravanan K