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TCAN4550-Q1: Clock freqency and accuracy

Koji Ikeda
Expert 5335 points
Part Number: TCAN4550-Q1
Other Parts Discussed in Thread: TCAN4550

Hello Support team,

Can TCAN4550-Q1 support only 20MHz for CAN-FD communication frequency? Can this device support 40MHz and 80MHz?

Could you show how accuracy TCAN4550-Q1 require for external clock on MCU or 40Hz external clock, to support CAN-FD communication?

Thanks,

Koji Ikeda

  • 0
    TI__Intellectual 2090 points

    The TCAN4550 can support 20 MHz or 40 MHz external clock or crystal input to the OSC1/OSC2 pins.  The required accuracy is 0.5% to support CAN-FD communication.

    Best Regards,

    Max Megee

    INT-TRX Applications

  • 0 in reply to Max Megee
    TI__Expert 5335 points
    Thank you for your support.

    *Is there any use case to set higher CAN-FD communication frequency by PLL? E.g. 20MHz -> PLL -> 40MHz and set 40Mzh for CAN-FD frequency.
    If yes, the accuracy is,
    Frequency accuracy on external clock + PLL frequency accuracy < required frequency accuracy spec for CAN-FD communication

    *CAN-FD requires 0.5% accuarncy, how about high speed CAN for low data rate? require higher or lower than 0.5%?

    Thanks,
    Koji Ikeda
  • 0 in reply to Koji Ikeda
    TI__Intellectual 2090 points

    Koji,

    I was unable to get to your request today, but please expect my feedback tomorrow.  Thank you for your patience.

    Best Regards,

    Max Megee

  • 0 in reply to Max Megee
    TI__Intellectual 2090 points
    Koji,

    I apologize for the delay in getting to your question. I need to make a revision to my previous comment above.

    Oscillator accuracy for Classic CAN communication rates (<1Mbps) is 0.5%.
    Oscillator accuracy for CAN-FD communication rates (1-5Mbps) is specified in the TCAN4550 datasheet at 0.15%. You can use a PLL to boost the oscillation frequency from 20MHz to 40MHz, but your total accuracy for the input to the TCAN4550 OSC1 and OSC2 pins must not exceed 0.15% when operating at CAN-FD speeds.

    Of course, you should be able to operate with larger format CAN-FD frames at lower speeds (<1Mbps) and the TCAN4550 should tolerate 0.5% oscillator accuracy.

    Does this help answer your question?

    Max Megee