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TCAN1043A-Q1: Correct Supplies for Remote Wake Up 3.3Vio and 5Vcc

Kevin Schmidgall
Expert 3860 points
Part Number: TCAN1043A-Q1

Hi,

I am reading through 8.4.1.5.1 checking the Figure 8-4 state diagram and have a couple questions -

  • do you need Vio during Sleep mode or can INH turn on Vio after a remote WU is received? I guess it just isnt clear to me when the INH will change states: before RXD is driven low or after. 
  • second question - from either the CAN protocol or experience with different OEMs, what is the typical transaction for a Remote WU?  
    • Is it - remote WU sent -> local host sends "ready to receive" message to let remote host know it is awake -> remote host sends message it woke up the local host for?
    • or does the remote host just start sending its message after the remote WU is sent assuming the local host has woken up
  • 0
    TI__Guru 53555 points

    Hi Kevin,

    Kevin Schmidgall said:
    do you need Vio during Sleep mode or can INH turn on Vio after a remote WU is received? I guess it just isnt clear to me when the INH will change states: before RXD is driven low or after. 

    The wake up pattern receiver and INH output are powered from the Vsup supply and can operate when Vio is not present. INH will drive high when the device wakes from Sleep mode into Standby mode as long as Vsup is supplied. 
    The RXD pin is supplied by Vio and is only active when this supply is available. After a wake from Sleep to Standby mode, RXD will remain high-z until Vio is supplied. Once this supply is available, RXD will drive low to indicate the pending wake request. 

    Kevin Schmidgall said:
    from either the CAN protocol or experience with different OEMs, what is the typical transaction for a Remote WU?

    There are many ways this can be implemented on a larger system level, so his can vary widely depending on the application. One solution is to have the remote node send a remote transmit request (RTR) to request data from the local node. This frame will be sent continuously until the remote nodes sees an ACK on the RTR frame. The local node will be in Sleep mode and will wake up to the first transmission of the RTR frame. Once awake and powered-up, the local node will connect to the CAN bus and be able to read a subsequent transmission of the RTR frame and ACK. The remote node sees the ACK and stops retransmitting the RTR. The local node will then send the requested data frame to the remote node. 

    There's a variety of other possible scenarios, so let me know if there's one in particular you think your customer is interested in. I hope the example gave you a good idea at the possibilities. 

    Let me know if you have any more questions.

    Regards,
    Eric Schott