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TCAN1145-Q1: TCAN1145 termination resistors

wade xiong
Prodigy 10 points
Part Number: TCAN1145-Q1


HI All:

          TCAN1145 as the  non-terminal node of CAN bus  .There are a total of 10 nodes on the bus,the length of the harness is 1.3m,What should  TCAN1145's  terminal resistor be.

          

  • 0
    TI__Guru 74322 points

    Wade,

    A termination resistor isn't always needed on the non-terminal nodes of the CAN bus. That being said, if you are going to put termination resistors on non-terminal nodes, you just want to make sure that the parallel combination of all termination resistors never goes below 55 ohms. With two terminal nodes at 120 ohms, and 8 other nodes with termination, I'd recommend a minimum of 6000 ohms at each non-terminal node.

    Please let us know if you have any other questions.

    Regards,

    Eric Hackett 

  • 0 in reply to Eric Hackett
    Prodigy 10 points

    Hi Eric：

               Thanks for the reply。

               The DUT inside the red box，  You mean the resistors of these DUTs need to be 6000ohm？

               There is another problem，these termination resistor of non-terminal nodes，how does it relate to the harness length and the number of nodes

              

  • 0 in reply to wade xiong
    TI__Guru 74322 points

    Wade,

    The number of nodes determines how many nodes will be in parallel with the 120 ohms of termination at both end nodes. So when calculating, you want to make sure that [node 1 termination] || [node 2 termination] || [node 3 termination] || ... || [node n termination] ≥ 55 ohms.

    The stub length is what determines if termination is needed at each middle node. The rule of thumb is if the stub length is 0.3 * the bus length or greater, termination at the middle nodes is recommended.

    Regards,

    Eric Hackett