• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 33 subscribers
  • Views 5583 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

TCAN1043-Q1: rise time and fall time spec

TCAN1043-Q1: CANBUS impendence

Zehui Li
Intellectual 540 points
Part Number: TCAN1043-Q1

Hi,

  Should I control the impendence of CANBUS trace on PCB?

  • +1
    TI__Mastermind 33140 points

    Hello Zehui,

    Controlling the impedance of elements of the CAN bus is always recommended, which would include the PCB. However this is not always practical and the benefits would be determined by how long the traces are.  If the traces are very short and the transceiver is placed very close to the wiring harness connector, then there will be little benefit because the impedance discontinuity from the connector and traces are all lumped together.

    However, if the transceiver is not near the wiring harness connector the traces become an continuation of the differential bus and impedance discontinuities from both the connector and the traces would be visible to the bus as separate discontinuities.  In this case impedance matching on the traces is recommended.

    Also, because CANH and CANL signals work as a differential pair, the routing should be differential with 120 ohm impedance if possible, or 60 ohms single ended with reference to GND.  The trace lenghts of CANH and CANL should also be routed as the same length and when routed as two single ended traces, they should have symmetrical routing so that they encounter the elements such as termination resistors, TVS diodes, filter caps, and common mode chokes at the same time. 

    Regards,

    Jonathan