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TCAN1044V: CAN transceiver is not waking up from Satndby mode

Part Number: TCAN1044V

Dear All,

I am facing an issue in my CAN transceiver circuit that is not able to come out from standby mode even if there is a valid CAN message in the CAN bus;

I have observed that the voltage at STB pin is always HIGH (more than 3.3V).

Please help me clarify below points

  1. Does it have an Internal pullup resistor in TCAN1044 so that the STB pin will be internally pulled up to HIGH during sleep mode?
  2. Is it possible to control the STB pin by MCU?
  3.  During wakeup from the standby mode how 
  4.  What will happen once there is a wakeup request (CAN message) over bus; Is the STB pin internally pulled down to LOW without intervention of MCU or the MCU needs to Pulldown it?

  • Harikrishnan,

    The wake-up signal on the bus does not automatically change the state of the TCAN1044V-Q1, this is totally controlled through the STB pin. The WUP signal will be detected by the transceiver while in Standby mode, cause RXD to toggle low as an indication to the MCU, and then the MCU will act by setting the STB pin low.

    1. Yes, there is an internal pull-up on STB in case the pin is left floating due to an MCU error. This guarantees that the device will be a low-power state in case there is a system fault.

    2. Yes, this is the intention, the MCU is meant to control this pin if Standby mode is desired.

    3. I think this question is incomplete.

    4. The MCU must pull down the STB pin, the WUP signal merely asserts the RXD pin low as an indication to the MCU that a WUP was received on the CAN bus.

    Please let us know if you have any other questions.

    Regards,

    Eric Hackett