DP83867IR: Connect 2 PHY togeter on the same PCB

Hi Andrei,

The DP83867 does not support 1Gbps capacitive coupling. However, the DP83869 PHY does support capacitive coupling at 1Gbps. 

I am not familiar with using a single transformer topology between two PHYs, this is something I can review with our validation team. Would the DP83869 capacitive coupling setup work for your application?

Regards,
Justin 

Hi Justin,

Thank you for your feedback.

Can you please check with the validation team if 1 transformer solution (instead of 2) works and also can you please confirm if the connection is limited bay the smaller length and smaller attenuation of the bus?

Thanks,

Andrei

PS: I'll take a look at DP83869 as well.

Hi Andrei,

Can you provide more information on the application you are targeting a single transformer for? What is driving the need for two PHYs connected over a single PCB?

Would capacitive coupling or perhaps the DP83869 in a media converter or bridge mode be appropriate?

Regards,
Justin 

Hi Justin,

There are 2 redundant systems that needs to communicate over ethernet and require insulation for safety reason.

If I use DP83867IR the only way is to replace the communication cable with PCB traces; now from insulation perspective one transformer should be enough, so I'm wondering if it is possible to use a singe transformer to bridge those 2 PHYs?

Now, for capacitive insulation a media converter is a good suggestion; I have just to connect together the fiber SERDES; I'm not sure if the capacitive will be accepted so I have to keep as primary option the transformer based insulation.

So, my questions remains:

- can I use just one transformer?

- the fact that the distance between the 2 PHYs is small (~50mm) this will affect the communication? It will be necessary a signal attenuation?

Thanks again,

Andrei

Hi Andrei,

Yes, you can use one transformer as isolation between two PHYs. 

You can refer to the E2E thread here for short cable, or trace, length applications for the DP83867 to ensure proper link up:

https://e2e.ti.com/support/interface/f/138/t/956902

Regards,
Justin 

Hi Justin,

Thanks for your feedback. Please clarify the followings:

1. If one transformer can be used, that means a 3 core regular 1:1 Ethernet transformer will do the job (even is not symmetrical in terms of coils arrangements)? One PHY will be connected in one side and the other on the other side?

2. If those new registers are set with the proper values (that you suggest in above thread), this will fix the DSP convergence issues for (small cables) for the current hw revision of PHY?

Thanks again and Most Appreciate your support,

Best Regards,

Andrei