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TCAN1044A-Q1: Does TCAN1044 and TCAN1043 need common-mode choke in design?

Kygo Cheng
Expert 6830 points
Part Number: TCAN1044A-Q1
Other Parts Discussed in Thread: TCAN1043

Hi Team,

There is a good new that we could DIN TI product!

Does TCAN1044 and TCAN1043 need common-mode choke in design?
It seem from datasheets there is no requirement, but it is recommended that common-mode choke can be reserved.

1. Is there any reference standard for this part of the design, or does TI CAN Transceiver have improved those features?
2. If the CAN Transceiver is the same, is there no need for choke in the design of CAN (500k/s) and CAN FD (5M/s)? 

thank you

  • 0
    TI__Mastermind 48215 points

    Hi Kygo,

    Common mode chokes (CMC) are passive devices that reject common mode signals on differential lines. The main impact of one of these components in a CAN system is to reduce radiated emissions caused by common mode noise from a transceiver and filter received common mode noise so it does not propagate to any local signals. The radiated emissions and emissions immunity performance applies in CAN systems that need to conform to a specification which defines behaviors for such behaviors. This includes things like Zwickau, J2962, and C&S. We can provide reports for these specifications, most of the time showing results with a CMC included (sometimes also without CMC). 

    If emissions behavior is not a concern for the end equipment, it is perfectly fine to use a CAN transceiver (or other differential transceiver) without a common mode choke. The ISO 11898-2 CAN standard does not require the use of one, and all of our supported CAN transceivers (that follow the ISO spec) may be used without a CMC. 

    Let me know if this is clear and if you have any more questions.

    Regards,
    Eric Schott

  • 0 in reply to Eric Schott1
    TI__Expert 6830 points

    Hi Eric,

    For the necessity of Common mode chokes, as mentioned in the TI data (as the attachment),
    The transition times and timing skew between the CANH and CANL lines, as they transition between dominant and recessive states,need to be well-matched to limit the common-mode noise occurring in high frequency bands.

    It seems that our device has improved for transition times and timing skew,
    Is there any detailed data or comparison data for testing customer design review requires supporting information, thanks!!

    slly020.pdf

  • +1 in reply to Kygo Cheng
    TI__Mastermind 48215 points

    Hi Kygo,

    The Zwickau reports for TCAN1044A and TCAN1043A contain EMC test results for both with and without a CMC included on the bus. Do you think this sounds like what the customer is looking for?

    These reports are available on our internal sharepoint. Please send me an email if you would like help locating them. 

    Regards,
    Eric Schott