TMDSCNCD28388D: preferred placement between MCU MAC through PHY and PHY through transformer

Hi Pablo,

A TI expert on this matter has been notified and will respond to you shortly.

Best,

Kevin

Pablo,

at 60mm your trace lengths should be OK according to the layout recommendations found on the product's page: http://www.ti.com/lit/pdf/snla079

I suspect you would want the differential signals to run a longer distance as they are typically more immune to noise, however I am not an expert for the DP83822.

To get you the best answer I will request a moderator move this over to the Interface forum.

Regards,
Cody 

Okey, thanks Cody. At first I think the same, but after reading the PHY IC datasheet it seems MDI is more susceptible to unbalanced traces than MII. For example the traces must go always on same layer, but  MII no. I guess that it is doubt that MDI is about 100mhz or more depending on codification and MII no more than 25mhz..

But I'll read what others recommend on that.

Thanks!

Best regards.

Pablo Slavkin

Hello Pablo,

Assuming the three components are in somewhat a straight line as you pictured, what is the distance between the MAC and magnetics?

Thanks,

Vibhu

Hi, Vibhu, thanks for the reply.

I put these on my first question:

"The total distance beteern MCU and  transformer is about 60mm"

The decision I've to take is where to put the PHY IC. near magnetics or near MAC, to keep the signal integrity of both interfaces at good shape.

And by the way, is the MII signal clk 25Mhz maximun, isn't it? and what about MDI bandwith??

Thanks!

Pablo

Hello Pablo,

60 mm is a short distance, and where you place the PHY in that space should not matter too much. If you really want to pick a side I would place is closer to the MAC interface.

Thanks,

Vibhu