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DP83822I: About characteristic impedance of RMII signals

tatsuro tokugawa
Prodigy 130 points
Part Number: DP83822I

Hi team,

I'm developing a PCB with the DP83822IRHBT.

I have a question about the characteristic impedance of RMII.
Section 9.2.2.2.2 states that the characteristic impedance of the pattern should be 50Ω.
The following signals are defined as RMII signals in Table 8-2.
 TX_D[1:0]
 RX_D[1:0]
 TX_EN
 CRS_DV
Is it okay to understand that there is no need to manage the characteristic impedance of the following signals?
 MDC
 MDIO
 XI
 RX_CLK

Best Regards,

  • 0
    TI__Mastermind 26752 points

    Hi Tatsuro,

    Let me check with the team on this. Due to Holiday season, I will get back to you next week.

    Thanks,

    David

  • 0 in reply to David Creger
    TI__Mastermind 26752 points

    Hi Tatsuro,

    As per section 11 of the datasheet:

    "Unless mentioned otherwise, all signal traces should be 50-Ω single-ended impedance. Differential traces should be 50-Ω single-ended and 100-Ω differential. Take care to ensure impedance is controlled throughout. Impedance discontinuities will cause reflections leading to emissions and signal integrity issues. Stubs should be avoided on all signal traces, especially differential signal pairs."

    Please see section 11 for further layout guidelines.

    Thanks,

    David