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TCAN1042GV-Q1: Does TCAN support short can activity filter?

Wayne Liu
Expert 8605 points
Part Number: TCAN1042GV-Q1

Hi

Does TCAN support short CAN activity filter? Thanks. 

  • 0
    TI__Guru 62910 points

    Hi Wayne,

    Yes.  The ISO 11898-2:2016 standard defines a short filter time ranging from 0.15 us to 1.8 us and a long filter time ranging from 0.5 us to 5 us.  The TCAN1042's activity filter is specified as 0.5 us minimum to 1.8 us maximum.  So, it is able to meet the requirements of both the short and long activity filters.

    Please let us know if you have any further questions.

    Regards,
    Max

  • 0 in reply to Max Robertson
    TI__Expert 8605 points

    Max,

    Thanks for your support.

    Further question: if the signal is 3us which is long, if it can pass through the filter or not? If the time is configurable? Customer needs the short option. Please send me more detailed material about the filter if you have. Thanks. 

  • 0 in reply to Wayne Liu
    TI__Guru 62910 points

    Hi Wayne,

    The filter time is not configurable.  It has a minimum duration of 0.5 us and a maximum duration of 1.8 us.  Any states longer than the filter period will count towards the wake-up pattern criteria, and any dominant periods will pass through to the receiver after the filter duration has been exceeded.  So, a 3 us signal will pass through.  I recommend reading through Section 9.4.3.1 in the datasheet to get a better understanding of how the filter works.

    This device will work whether the customer needs to support the short filter or the long filter.  This is a special feature of this transceiver that was intended to make it easier for customers to support a variety of applications.

    Let us know if you have further questions.

    Regards,
    Max

  • 0 in reply to Max Robertson
    TI__Expert 8605 points

    Hi Max,

    Understood. Thanks.

    So if the chip supports short filter, it must supports long filter, right?

    If the signal is 1.6us, TCAN maybe or MUST treat it as WUP? I think it is maybe because it is in the range of 0.5 to 1.8. Why didn't we design the twk_filter to narrower such to better support short filter? 

  • 0 in reply to Wayne Liu
    TI__Guru 62910 points

    Hi Wayne,

    A chip supporting the short filter doesn't necessarily support the long one automatically.  For example, a device supporting the short filter may pass periods of 0.4 us, which should not occur when using the long filter.

    One way to think of it is:

    For the short filter, anything less 0.15 us must not pass.  Anything greater than 1.8 us must pass.  Anything in between may or may not pass.

    For the long filter, anything less than 0.5 us must not pass.  Anything greater than 5 us must pass.  Anything in between may or may not pass.

    For the TCAN1042, anything less than 0.5 us must not pass.  Anything greater than 1.8 us must pass.  Anything in between may or may not pass.

    Therefore, TCAN1042 fully supports either filter option.

    Regards,
    Max

  • 0 in reply to Max Robertson
    TI__Expert 8605 points

    Max,

    Clear, thanks!