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TCAN1043HG-Q1: How to know if INH is high because of KL30(power on) in on or CAN wakeup?

Somdut Dey
Prodigy 80 points
Part Number: TCAN1043HG-Q1

Hi,

In the datasheet of TCAN1043HG-Q1 it is mentioned that in standby mode INH is high. INH is typically used to Enable 3.3 V power which goes to micro (ref: Application Information section). So if CAN transceiver is in standby mode micro will get powered. CAN transceiver could come to standby mode from internal state or from initial 5 V power up (KL30 on, power chip 5 V on). CAN transceiver can go into standby mode by CAN wakeup from other internal state.My questions are

1.How micro will come to know whether it got powered due CAN wakeup or  KL30 on (initial CAN power up)?

2. OEM is asking not to power up micro without CAN wake up. It seems first time CAN transceiver  gets power it turns on micro . If this is not acceptable what are the changes that needs be done at circuit level or software level to implement the same? 

  • 0
    TI__Guru 64872 points

    Somdut,

    You are correct, on initial power-up and from a wake event, the device will go into Standby mode and INH will be high.

    1. One way to determine whether the device was powered due to CAN wake up or KL30 is by immediately switching to Silent mode and monitoring the nFAULT pin. Once the micro powers on due to Standby mode and INH setting high, the EN pin can be set low and the nSTB pin can be set high to go into silent mode. Once in silent mode, the nFAULT pin will indicate low for initial power up, and high for a WAKE event.
    2. The goal is to keep INH low as to not enable the power supply and power the MCU. If it's possible to keep nSTB low and EN high on power up to switch immediately into Sleep mode on power up? Or is there a way to not supply VCC or VIO on power up, and then supply it after VSUP is supplied? This should transition the device straight into Sleep mode.

    Regards,