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DP83867IR: About characteristic impedance of RGMII signals

tatsuro tokugawa
Prodigy 130 points
Part Number: DP83867IR


Hi team,

I'm developing a PCB with the DP83867IRRGZR.

I have a question about the characteristic impedance of RGMII signals.
Section 9.2.2.1.1 states that the characteristic impedance of the pattern should be 50Ω.

Are all single-ended signals connected to the DP83867IRRGZR covered?
Is it necessary to control 50Ω for signals like following?
 RX_ER
 MDC
 MDIO

Best Regards,

  • 0
    TI__Mastermind 27212 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 27212 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 that the impedance is constant throughout. Impedance discontinuities cause reflections leading to EMI & signal integrity problems. Stubs must be avoided on all signal traces, especially the differential signal pairs"

    Please see section 11 for further layout guidelines.

    Thanks,

    David

  • 0 in reply to David Creger
    Prodigy 130 points

    Hello David-san

    Thank you for your reply.

    Section 11 states:
    Length matching is also important on MAC interface. All Transmit signal trace lengths must match to each other and all Receive signal trace lengths must match to each other.

    MDIO is an input/output signal synchronized with MDC.
    Should I make equal length between MDC and MDIO signals separately from other single signals?

    Best Regards,
    Tatsuro

  • +1 in reply to tatsuro tokugawa
    TI__Mastermind 27212 points

    Hi Tatsuro,

    MDC/MDIO do not need to be length matched as long as they meet the timing requirements described in section 22.3.4 of the IEEE802.3 standard.

    Thanks,

    David