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TCAN1042GV-Q1: Vcc=0V with STBY=L issue

Nick Hsiao19
Intellectual 615 points
Part Number: TCAN1042GV-Q1

Hello Team,

I got below issue while Vcc=0V && STBY=L, the CAN transceiver goes into protected mode. The RXD gets high level in such a condition.

In my application, the only IO of my product is VBAT(12V)\GND\CAN, so if I goes into protected mode, no one can help me get away from it. To avoid the risk permanently, I am thinking changing my circuitry as below diagram, how do you think? is there any trouble in the solution circuitry?

Thanks.

  • 0
    TI__Guru 62910 points

    Hi Nick,

    I may be misunderstanding your issue. Why not just drive STB high while VCC is unpowered to keep the device in standby mode until a wake request is received (resulting in a high to low transition on RXD)? Then the MCU could enable the 5-V regulator and transition the transceiver to normal mode by pulling STB low.

    Max

  • 0 in reply to Max Robertson
    Intellectual 615 points

    Hi Max,

    I am just worried about if there is any possibility that MCU drives CAN transceiver into protected mode (VCC unpowered, and STBY=L). In that case, the RXD would never response anymore. For my product, the only communication interface is CAN, so I have to guarantee the RXD is always active in every situation.

    Regards,

    Nick.

  • 0 in reply to Nick Hsiao19
    TI__Guru 62910 points

    Hi Nick,

    I understand the concern now.  It seems that your proposed circuit could help ensure a high state on STB when the MCU output is high-Z, but if the MCU output is in the wrong state I believe it would still cause issues.  If you just want to protect against the case of a high-Z MCU output, though, you could simply use a pull-up resistor on STB (without the NMOS).  Let me know if this doesn't make sense or if I'm missing something.

    Regards,
    Max

  • 0 in reply to Max Robertson
    Intellectual 615 points

    Hi Max,

    yes, have a pull-up resistor is simple and should be workable. Thanks for the help.

    Regards,

    Nick.