DP83TC813R-Q1: RMII and MDI trace lengths

Hello Jessica,

I will discuss this internally and get back to you 5/30.

Regards,

Avtar

Thank you for the quick response and the feedback.  

Hello Jessica, 

You are welcome, please let me know if you have any other layout questions. 

Regards,
Avtar

Should the ground plane be continuous under the CMC and termination components as well?  I have seen in some app notes that the ground (and all copper layers) should be cutout from under the CMC.

Hello Jessica,

Yes that is recommended as well, cutting out ground from under CMC and termination components. 

Regards,
Avtar

Unfortunately given my layout I can only do the cutouts under the CMC, not around the other termination components.  Is that sufficient?

Hello Jessica,

It's hard to give a guarantee as there are so many factors for layout, cutout around termination components is recommended however in some cases it may be ok without. 

Regards,
Avtar

What would be the effect if it turns out cutouts were necessary?  Does it affect the operation of the ethernet communication or is the end effect related to EMC performance?

Hello Jessica, 

Mainly EMC performance, and in some cases ethernet communication. Is it possible at all to include these cutouts?

Regards,

Avtar

I can make the cutouts in the ground planes, but there are some traces which cross over on different layers which will be difficult to reroute.

Hello Jessica,

I understand. Currently is there a ground plane as well as traces underneath CMC components? If so I would suggest rerouting those traces and making a cutout in the ground plane. 

Regards,
Avtar

I've cleared out all copper from all layers under the CMC, for the series capacitors and termination components I have kept the ground plane and traces on other layers.  I am working on clearing out the copper from under those components, but there are still be some traces which run perpendicular to the TRDP/TRDM traces on the opposite side of the board.

Hello Jessica,

Perpendicular traces underneath will cause issues, I would recommend trying to reroute. 

Regards,

Avtar

Will do.  Thank you very much for the advice and the quick responses!

Hello Jessica, 

You are welcome, let me know if you have any other questions.