DP83620: RMII routing guidelines - length matching tolerance

Premalatha Royappan

Part Number: DP83620
Other Parts Discussed in Thread: AM625

We are using DP83620SQE this in our design. We want to know : whats the length matching tolerance we need to follow for RMII, whether its 2 inches or 50 mils. We are seeing this tolerance different in these reference documents from TI.

https://www.ti.com/lit/an/snla079d/snla079d.pdf?ts=1680607009631&ref_url=https%253A%252F%252Fwww.google.com%252F

https://www.ti.com/lit/an/snla387/snla387.pdf?ts=1671479582953&ref_url=https%253A%252F%252Fwww.google.com%252F

Also we want to know if there are any additional guidelines that length of clock needs to be half that of data. This we are finding in AM625x schematics checklist. We are using AM625 processor in our design.

https://www.ti.com/lit/an/sprad21a/sprad21a.pdf?ts=1680670633883&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FAM62A7

over 2 years ago

0 Hillman Lin over 2 years ago

TI__Mastermind 25955 points

Hi Premalatha,

Here are some comments for following questions:

Sorry for the confusion, the length matching tolerance should be 50 mils.
Regarding to the second question, length of the clock trace should have equal distance with the data path. The paragraph you send me seems like they want to put a buffer half way between the clock signal would help with the AM625. If you have further question on the clock buffer, I think AM625 processor team would be a better contact.

Thank you,

Hillman Lin

0 Premalatha Royappan over 2 years ago in reply to Hillman Lin

Intellectual 910 points

In PHY slave mode ,please confirm if length of the RMII clock trace needs to be equal to that of the data trace or half that of the data trace.

0 Vikram Sharma over 2 years ago in reply to Premalatha Royappan

TI__Genius 16030 points

Premalatha,

We are internally assigning this query to processor team to get their feedback about this routing. Team will get back to you shortly.

Regards,

Vikram

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DP83620: RMII routing guidelines - length matching tolerance