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CAN Differential signal isolation using two SN65HVD234D

Arun Achoora
Prodigy 30 points
Other Parts Discussed in Thread: ISO1050

Hi,

Can we isolate two CAN differential signal using two SN65HVD234D's and a Digital isolator in between without any CAN controller(such as Microcontroller) interface.Circuit is attached.Please let me know your views.

  • 0
    TI__Guru 62910 points
    Hi Arun,

    With this circuit, any single dominant bit would cause the bus to be stuck dominant. (For example, if the bus connected to U26 is dominant, its RXD would go low, then the TXD input of U28 would go low, then the U28 CAN output would be dominant, making its RXD output also low, which then makes the U26 output dominant, etc.)

    Would it be possible to simply use isolated CAN transceivers (like ISO1050) instead? That tends to be the usual approach to this problem.

    Best regards,
    Max
  • 0 in reply to Miguel Robertson
    Prodigy 30 points

    Hi Max,

    Thanks a lot for making things very clear. We already have a CAN transceiver in place which is isolated. But for this particular section we want even the same CAN and all associated circuitries to be isolated from the rest of the system. So do you mean I can use two ISO1050 in the similar configuration(without ADUM Isolator chip)?

    In simple words can we isolate a differential CAN signal with out the intelligence(say a microcontroller) in between?

    Thanks for your quick support.

  • 0 in reply to Arun Achoora
    TI__Guru 62910 points
    Arun,

    No, simply changing to ISO1050 wouldn't be able to resolve the issues with this configuration. I was thinking you could use that device as the CAN transceiver on either end of the link rather than trying to add isolation to an existing CAN bus. It sounds like that may not be an option for you, though. You wouldn't necessarily need a full controller device in order to accomplish this, but you would need to implement some kind of logic between the two CAN transceivers (using the TXD and RXD signals) to ensure that dominant signals propagate through correctly without locking up the repeater.

    Best regards,
    Max
  • 0
    Prodigy 10 points

    Hi!

    I know this thread is over a year old, I am answering anyway.

    There is a design suggestion for an insulated RS485 hub. This may give you some ideas for the same thing with CAN.

    Look at that document: