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About CAN Transceiver communication

Gary An
Intellectual 440 points

Hi all,

I knew that the nodes(ECUs) have to be inside of Rts (120ohm).

Can the nodes be connected next to the Rt (not inside of Rt) like red circle on the below picture?

If yes, how long the node can be far from the Rt?

How many ECUs can be connected on the CAN line?

Thank you

  • 0
    TI__Guru 62920 points

    Hi Gary,

    The distance from the bus to an unterminated branch is equivalent to the stub length you asked about in your other post:

    https://e2e.ti.com/support/interface/f/138/p/907490/3354215

    For example, the distance between Rt on the right side and the right-most node that you circled would act like a stub,

    As for the number of nodes, it is influenced by a few things:

    1. The cumulative impact to signal integrity from the wiring of all nodes.

    2. The total capacitive loading, which can introduce timing distortion onto the waveforms by slowing down edge transitions.

    3. The input leakage current to each transceiver due to the receiver input impedance.  (All nodes will act in parallel, so each additional node decreases the overall bus impedance and increases the output current that must be sourced from each driver.)

    You may want to reference Section 4.12 of this application note for further details:

    http://www.ti.com/lit/an/slla270/slla270.pdf

    Regards,
    Max