DP83822I: MDI signal trace length maximum

Hi Geet,

I'm aware of this document but thanks for the hint anyway. It contains lots of useful information. But still I wasn't able to find answers to some of the questions in this thread.

MDI signals: I only found:
-  "PCB trace length should be kept as short as possible"
- "...should be run parallel to each other and matched in length."
It would be interesting having a absolut length limit. Something like "We would not recommend going beyond 4 inch" (like it is written in that document for the MII signals)
What is "matched in length"? Is 5mm still ok or do we even have to have a automatic lengthening while routing (like meanders). It would help a lot if an expert would say something like "stay within 5mm difference within a differential pair and you will be fine" (as long as all other contraints are fulfilled).

MII signals:
I have found the 2 inch rule for the matching. As of my understanding I can route "TX_CLK" 2 inch in length and route "TX_D0" 4 inch in length (as absolut maximum). Correct?

Thanks and best regards,

Patrick 

Hi Geet,

Thanks for the link. This answers one of the questions.


Can you give me an answer for my interpretation of the MII signal constraint?

Regards,
Patrick