Thanks for the help, those were some great pointers!
I’ve now gone and looked at the PHY chip on the client side and it’s a TI DP83848J. It looks like it recommends 3.3V for the pull-ups and transformer CT’s in the design guidelines. I also found an Application Note in the TI website discussing transformer-less operation with this exact PHY chip which is a great indication it may be doable (I provide links to all documents below)
TI DP83848J datasheet: ti.com/lit/ds/symlink/dp83848j.pdf
Application note on Transformerless Operation: ti.com/lit/an/snla088a/snla088a.pdf
Ralink Chip datasheet: tracermcc.ru/foto/bender/RT3 … 8_0902.pdf
Now, the issue I’m facing is that the Ralink chip on the WizFi630 apparently has the PHY module embedded in it, but I can’t find any useful information or references in it’s datasheet talking about transformer selection guidelines, transformer CT voltage, transformer-less operation of anything useful. And also, the WizFi630 HW design guide shows the CT’s pulled up to 1.8V which I find concerning.
Do you have any other advise on how to punch my way through this?