DP83867IS: Direct PHY to PHY connection with KDZ9893R

Hi,

As defined in the datasheet, magnetics are required for the MDI lines to ensure proper functioning of the PHY, especially at gigabit speeds.

This section of the datasheet outlines the requirements for the magnetics required for the DP83867

Best,

Vivaan

Hi Vivaan, would this be the wiring? I couldn't find any reference design on direct PHY-PHY connection.

Hi, 

It would be recommended to use 2 separate magnetics for each PHY for proper functionality instead of the 1 pictured above. Each PHYs datasheet includes guidelines on what magnetics to use. The ends of these magnetics can simply be connected together.

Just out of curiosity, what application are you trying to build with this setup? Usually the magnetics are followed by an RJ45 connector to connect an ethernet cable to, which in turn connects to the link partner PHY. In this implementation, it looks like the RJ45/Cable connection is being bypassed to directly interface the PHYs together.

Best,

Vivaan

Happy Holidays Vivaan! yes, RJ45/cable not needed as these components will be on the same PCB; distance between DP83867E and EP83869 is around 20-30mm.

I guess no choice but to put two separate magnetics.

Hi Rue, 

Happy holidays! Unfortunately, we do recommend having separate magnetics for DC isolation and EMC performance reasons. If you don't have any other queries, I will now be closing this thread but you could always reply back here or create another thread if you need more support. 

Best.

Vivaan

Hi Vivaan, here is the update:

Should I still require R2, R4, R6, R8, and C10?

Again, thank you for your support on this project.

Hi, 

Yes, this would be a better implementation. One of my concerns is that the center taps look to be shorted since all of them connect to the same net for the ferrite beads. We have noticed that shorting these center taps has caused some link issues previously and it is not recommended to do that. Is there any particular reason for the ferrite beads?

Best,

Vivaan

should i keep center taps unconnected like this?