Pairing PHY chips with Gigabit network transformers is less “universal” than I expected I’ve been validating a few 1000Base-T designs recently, and something that looked simple at first ended up taking more time than expected: getting the PHY and the network transformer to behave nicely together. At the beginning, I assumed most Gigabit Ethernet magnetics were basically interchangeable as long as: the pinout matched the impedance matched and the datasheet said “1000Base-T compatible” But after testing a few combinations, it became pretty obvious that the PHY + transformer relationship is more sensitive than I originally thought. The issue wasn’t link-up — it was stability Interestingly, almost every setup I tried could establish a link.…