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TCAN1043A-Q1: Baud rate deviation calculation

wenjun yang
Intellectual 360 points
Part Number: TCAN1043A-Q1

Tool/software:

Hello,TI expert

        we used to CAN FD bus communication by TCAN1043A-Q1  ,I have a question that how to calculation to baud rate deviation. thank you 

  • 0
    TI__Guru 74252 points

    Wenjun,

    What is your question? Also, the baud rate deviation would be controlled by the controller, not the transceiver, but we can still try and help.

    Regards,

    Eric Hackett 

  • 0 in reply to Eric Hackett
    Intellectual 360 points

    Hi,Eric

         Thank you for your kindly support.

    Controller side is TDA4VE,and customer have a requirement that baud rate deviation is less than 0.1%.I dont't know how to calculation baud rate tolerance,could you help to me ?

  • 0 in reply to wenjun yang
    TI__Guru 53515 points

    Hi Wenjun,

    As Eric said, this is a parameter determined by the CAN controller in the system. Most often this applies to the crystal oscillator or other clock source used by the MCU to derive the bit duration of the CAN channel. For one of our CAN controllers for example, this would be a 40MHz crystal with a tolerance of +-0.5%. In your case it sounds like there are some more strict requirements that will apply to this clock source. I recommend looking at the clock source to your MCU, specifically which one is used to derive the source for the CAN controller (usually in the 20MHz - 80MHz range). 

    Please let us know if you have any further questions on the physical layer requirements or your CAN system which are determined more by the transceiver (TCAN1043A). 

    Regards,
    Eric Schott

  • 0 in reply to Eric Schott1
    Intellectual 360 points

    Hi,

        Thank you for your support

    CAN controller interface  is TDA4VE MCU_MCAN0,and TDA4VE clock input is 27MHZ ,50ppm.so how to evaluate baud rate deviation.

  • 0 in reply to wenjun yang
    TI__Mastermind 27500 points

    Hi Wenjun,

    Since Eric is out of office, I'm replying you here.

    ±50ppm means the tolerance is ±0.005%, which is also your baud rate deviation.

    Regards,

    Sean 

  • 0 in reply to wenjun yang
    TI__Guru 74252 points

    Wenjun,

    50ppm means the oscillator frequency has a tolerance of 50 parts per million, or 0.00005 (0.005%). This means that the oscillator frequency can range from 26.998650 MHz to 27001350 MHz. So, over time this could result in a large drift, but initially it is a small variation. 

    From here, it will be about the controller's tolerance as well, which would be a question better suited for the team that supports the controller. We only support the transceiver.

    Regards,

    Eric Hackett 

  • 0 in reply to Eric Hackett
    Intellectual 360 points

    Hi,Eric

        Thank you for your kindly support.