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TCAN2451-Q1: SWE_TIMER_SET register issue

Daniel Wang (auto)
Expert 3540 points
Part Number: TCAN2451-Q1

Tool/software:

Hello team,

Customer met an issue when design TCAN2451:

After powering on for 4.5 minutes, the VCC1 output will be turned off. It was found that the default register of the SWE_TIMER_SET was 4.5, that is, it would be turned off after 4.5 minutes (at this time, the SW pin had been pulled up and the watchdog was disabled, but it seems that the watchdog was still affected by the SWE_TIMER_SET register).
So there are two questions:

1 What was the original purpose for designing this register bit?
2 During development, if the SPI is not ready, does the debugging get stuck in a loop? Would it be better if this design was removed (VCC1 output guaranteed).

Thanks!

  • 0
    TI__Guru 74252 points

    Daniel,

    An expert has been assigned to this thread and will have a response by end of business 09/13/2024.

    Regards,

    Eric Hackett 

  • 0 in reply to Eric Hackett
    TI__Expert 3540 points

    Hello Eric,

    I didn't get response yet.

    Regards,

    Daniel Wang

  • 0 in reply to Daniel Wang (auto)
    TI__Mastermind 26806 points

    Daniel,

    Daniel Wang (auto) said:
    1 What was the original purpose for designing this register bit?

    The SWE timer helps reduce current consumption in failure cases by turning off the node if the MCU fails to wake up. For example, if a wake-up occurs, the ECU would become powered by VCC1. However, if the MCU fails to start up, then after 4.5 minutes (by default), then the node will turn off. This prevents the node from staying on indefinitely and draining the vehicle battery.

    Daniel Wang (auto) said:
    2 During development, if the SPI is not ready, does the debugging get stuck in a loop? Would it be better if this design was removed (VCC1 output guaranteed).

    In our experience, MCU startup routines should take <1sec. There are some cases where it needs more time, but I've never seen it need longer than 4.5 minutes (yet). Additionally, for board debugging, generally this is completed in a few seconds or maybe 1-2 minutes. If the board needs to be debugged longer, then the user would either need to transition the TCAN2451-Q1 into Normal mode, or they would need to turn off the SWE timer using SWE_DIS.

    Best,

    Danny

  • 0 in reply to Danny Bacic
    TI__Prodigy 250 points

    Daniel,

    As Danny mentioned, SWE timer can be disabled after the device is in Standby mode after every POR. In ES_1.0 (current silicon), SWE is enabled by default.

    However, in the next revision of samples , SWE timer is disabled by default. Therefore, this should not be a concern anymore. Follow up with the team over emails on sample availability of the next revision of samples.

    Vrashank