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TCAN1043-Q1: Power-up reason detection

mykola Sliusarev
Prodigy 40 points
Part Number: TCAN1043-Q1

HI Experts,


We would like to determine power-up source between cold start or wake-up for sleep mode.
According to documentation we need to put transceiver in silent mode (nSTB == high ,  en == low)  and then read nFault status.

But actually results nFault pin is HIGH for both cases cold boot  and wake-up from sleep. In cold boot nFault pen keeps high after power is up and from sleep it become high after entering in silent mode. 

Could you please clarify how to correctly identify  Wake-up reason? 

Regards Mykola

  • +1
    TI__Guru 53575 points

    Hi Mykola,

    Thanks for sharing your question on E2E. 

    The behavior you describe is not what I would expect for the cold-start case. When Vsup is first supplied to the device,the PWRON flag will be set and is indicated on the nFAULT pin when the device is in silent mode. The PWRON flag is only cleared when the device enters normal mode.

    Please ensure that the device does not enter normal mode before running this test. I would advise keeping the nSTB and EN signals low during initial power on so that the device will stay in standby mode until the MCU is ready to drive the transceiver into silent mode to read the nFAULT state. 

    If this does not work, would you be able to share a scope shot of the EN, nSTB, and nFAULT signals during the power up condition? I would like to see the timing of the mode changes and ensure that there are no inadvertent mode changes.  

    Have you been able to evaluate the behavior of the WAKESR flag to ensure the device is properly recognizing local vs bus wake conditions? 

    Regards, 
    Eric Schott 

  • 0 in reply to Eric Schott1
    Prodigy 40 points

    HI Eric, 

    Thanks for your support it very helpful. 

    Finally we identify root cause  is that short spikes on En and nSTB due to inrush current.