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TCAN4550-Q1: Normal to sleep when there are messages on CAN

Grey Guo
Intellectual 2150 points
Part Number: TCAN4550-Q1

Tool/software:

Hi team,

My customer found when there are messages on CAN, they cannot use SPI command to let TCAN4550-Q1 enter sleep mode (enter standby first then enter sleep). nWKRQ remains low. Could you check about this? Thanks!

Best Regards

Grey

  • 0
    TI__Mastermind 33030 points

    Hi Grey,

    The TCAN4550-Q1 is not a partial networking device and any messages on the CAN will likely meet the requirements of the Wake Up Pattern (WUP) and wake up the device.  Therefore, the TCAN4550-Q1 can only be in sleep mode when there are not any CAN messages on the bus, and will likewise wake up when messages are present.

    In order to have a device that can be placed into sleep mode when CAN messages are present, the device needs to be capable of monitoring the CAN message ID's for specific values that will cause the device to wake up.  This is referred to as Partial Networking, or Selective Wake.  The TCAN4550-Q1 does not support this and will wake up on any CAN signals that meet the WUP requirements as outlined in section 8.4.3 of the datasheet.

    Regards,

    Jonathan

  • 0 in reply to Jonathan Nerger
    TI__Intellectual 2150 points

    Hi Jonathan,

    Thanks for reply. If customer wants to let TCAN4550-Q1 enter sleep mode, they must wait until there are no more messages on CAN bus, is that right?

    Best Regards

    Grey

  • +1 in reply to Grey Guo
    TI__Mastermind 33030 points

    Hi Grey,

    That is correct.  After the device has been placed into Sleep Mode, it will monitor the CAN bus for a Dominant, Recessive, Dominant pattern and then wake up once it has seen a Dominant, Recessive, and another Dominant bit or voltage level on the bus.  There is a filter time for each of these bits that needs to be met to help prevent false wake ups on noise, but most if not all valid CAN messages will meet the WUP criteria.

    Regards,

    Jonathan