PCB layer stack up for using the enc28j60

Other Hardware General Electronics
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Hey guys, I recently started a project on creating a module for PoE with enc28j30. I know that a 4-layer (signal, GND, GND, signal) stack-up would be the best choice, but is it overkill for a 10-base-T signal?

I am using a [ARJM11C7-114-BA-EW2] https://www.digikey.in/en/products/detail/abracon-llc/ARJM11C7-114-BA-EW2/7675237, which has the magnetics integrated. Here's a resource I found https://www.pulseelectronics.com/wp-content/uploads/2020/12/Pulse_Layout-Considerations-v7.pdf, according to this there should be no GND plane under the jack right? Pls, mention the points that I should take from the guide. Is it ok to use bigger packages such as 0603 or 0805. I also saw in the enc28j60 breakout board schematic that a 49.9 1%ohm resistor is used, why is this bizarre value? Can I use 50ohm instead? Why is there a transformer in parallel or series in the magnetics?

Pls do pardon me if I am saying something stupid. I am an absolute beginner in PCB design, so feel free to give any advice.

Thanks in advance😊

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You can't possible be a beginner. My company used to build circuit boards for beginners at a local university engineering program. They were ALWAYS single sided and one IC and a few other components.

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Well, unfortunately, I am a beginner. I have never designed a PCB before. I wanted to implement this on a PCB because I don't think it's practical to implement high-speed designs on a breadboard. Bit of a long shot. That's why I need every single detail about the design from u guys.

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