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CAN transceiver (SN65HVD1040) split functions issue

martin kanka
Prodigy 60 points
Other Parts Discussed in Thread: SN65HVD1040

Hello,

I have 4 pcb boards that all do not communicate on the CAN bus when the SN65HVD1040 driver is setup with the split function on these boards.

The resistance between CAN-H and CAN-l pins on the board with it disconnected and powered down is:

53K Ohms (no terminating resistor - resistance between the two pins)

120 Ohms (with 120 Ohms terminating resistor)

14 Ohms (with two 60.4 Ohms and 10 nF capacitor as the terminating network - this would be the split function)

Other nodes on the CAN bus go into error mode immediately when attempting to communicate, and when the split function node attempts to communicate it does not even generate any differential signals on the bus.

Removing the split function network on the board with no termination removes the problem, also using the 120 Ohms resistor removes the problem. The CAN bus has via other nodes 120 Ohms termination regardless of the offending split function node.

Why the low low termination of the split function, and what could I be doing wrong?

Thanks!

  • 0
    TI__Mastermind 21543 points

    Hi Martin,

    Would you be able to share a schematic and some oscilloscope pictures?

    Also have you performed any system level testing on the devices before doing this test?

    Thanks,

    John

  • 0 in reply to John Griffith
    Prodigy 60 points

    Well after assembling and testing several other boards, it would seem the problem is gone (or never was)! I have no good explanation why incorrect terminating resistances on the original boards other than maybe PCB construction defects?

    As always not much time to investigate the issue further, but thank you for attempting to assist me John! I really wish I had more feedback.