Hello,
I'm designing an embedded system that has a Cirrus Logic CS8900A ethernet controller and the recommended Pulse Engineering E2023 transformer. As far as the RJ-45 connectors go, I would like to get some feedback on what options should I look for and what are their benefits, in particular filtering and shielding.
I'm looking at the Corcom RJ45-8N3-B from Digikey at the moment, since Digikey components are the easiest to source for me. This is a block-filtered, modular connector with shielding.
(1) What are the differences between block and sleeve filtering?
(2) The CS8900A requires a 1:2.5 turns ratio in my transformer, which the E2023 meets, but does the filtering in the Corcom connector effectively change the circuit properties set by this turns ratio? Will this Corcom connector work with the CS8900A in 3.3V mode?
A shielded connector would primarily be useful to me if it prevents EMI that would otherwise adversly affect other parts of my circuit (This is a hobbyist project, so FCC Part 15 is not a priority).
(3) Is the purpose of connector shielding to prevent EMI with the outside world or with the rest of the PCB?
(4) At a minimum, how far away from other chips on the PCB should the connector and transformer be placed? Should the transformer be placed close to the connector?
As a last somewhat unrelated question, what does the CS8900A an83-3 application note mean when is says that I should "void ground/power plane from transformer to RJ45"? Does this mean the plane should have no components/traces above it, or does this mean that there should be no plane here?
Cheers, Chris