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TCAN4550-Q1: Abnormality in Standby

Wayne Liu
Expert 8605 points
Part Number: TCAN4550-Q1
Other Parts Discussed in Thread: TCAN4550

Hi,

Case 1:

1. The bus is active with CANFD package is over 8 bytes

2. TCAN4550 is in standby mode, it is normal until 4 minutes passes. The abnormality is as below, 

3. Even goes to normal mode, the fault doesn't disappear.

Case 2:

1. The bus is active with diagnostic package, 8 bytes

2. TCAN4550 is in standby mode, it is normal until 4 minutes passes, the abnormality is as below, 

3. Even goes to normal mode, the fault doesn't disappear.

Case 3:

1. No package on bus

2. TCAN4550 is in standby mode and keep in silence for 10 minutes, it is normal.

My question is , why there is abnormality after 4 minutes in standby mode? Where am I wrong? 

Thank you very much

  • 0
    TI__Mastermind 47895 points

    Hi Wayne, 

    This behavior sounds like the SWE timer (tINACTIVE) timing out and placing the TCAN4550 into Sleep mode. When the device receives a wake up event such as a WUP on the CAN bus and the device enters (or is already in) Standby mode, the SWE timer will start. If the device does not enter Normal mode within tINACTIVE, the device will automatically go into Sleep mode. While in Sleep mode, SPI is not available so values read from this interface may be viewed as a constant lows or highs (all 0s or all 1s). 

    When there is no traffic on the CAN bus, the device never receives a wake event and the SWE timer never starts, therefore allowing the device to remain in Standby mode. 

    To disable this timer after initial power-up, the SWE_DIS field in the Mode Control register (h0800) can be set. This will prevent the 4 minute timer from starting due to a wake event into Standby mode.

    Let me know if this suggestion solves the behavior here and if you have any more questions.

    Regards,
    Eric Schott

  • 0 in reply to Eric Schott1
    TI__Expert 8605 points

    Eric

    Makes sense. Thank you so much for your quick response. Let me try your suggestions.