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TCAN1145-Q1: Automatic Transition from Normal to Sleep

Erin Jacklin
Prodigy 10 points
Part Number: TCAN1145-Q1

Tool/software:

I have a design in which the INH pin is being used to enable a regulator. I need this regulator enabled most of the time which means keeping the TCAN1145 in Normal or Standby mode to ensure INH is high.

I noticed that while in Normal mode after a certain amount of time it automatically transitions to Sleep if no traffic is received (sending doesn't seem to matter). There is no guarantee of receiving CAN messages before t-inactive expires to keep it in Normal or Standby. What is the best way to ensure that I can indefinitely keep INH high until I actively tell the device to sleep?

Also, I'm struggling to understand how t-silence and t-inactive are coupled in this scenario. Any idea?

  • +1
    TI__Mastermind 27680 points

    Hi Erin,

    Thanks for your posting on E2E.

    The reason it's going to sleep mode is the SWE timer, if there's no CAN activity longer than tSILENCE the SWE timer will start, and once it expires (about 4 mins) the device enters sleep mode.

    You can set CANSLNT_SWE_DIS = 0, and then periodically clear the CANSLNT interrupt to clear the SWE timer.

    Regards,

    Sean

  • 0 in reply to Sean Guo
    Prodigy 10 points

    Thank you Sean, that fixes my problem and keeps the chip alive. What isn't very clear in the datasheet is writing 0xFF is how you clear the whole interrupt register so that caught me up for a bit.

  • +1 in reply to Erin Jacklin
    TI__Mastermind 27680 points

    Hi Erin,

    If you don't need SWE timer in normal mode, there is another way to keep the device in normal mode. The first SWE timer at power-on is only disabled by changing states or clearing PWRON. After that, if you set SWE_DIS=1, it will never run again. If you leave SWE_DIS=0, then it can start again in various other states, such as Normal mode (as you listed, and in my last reply) or in Failsafe mode, or getting a new wake event in Standby mode.

    Regards,

    Sean

  • 0 in reply to Sean Guo
    Prodigy 10 points

    This is more of what I was looking for so I don't have to keep clearing the interrupts. Thank you!