W5500io transformer selection

Question

Hi, I’m successfully using W5500 modules with RJ45s in my designs, but I’ve got one that’s space-constrained so I’m using the W5500io with an external pulse transformer and a different connector. Can someone recommend a transformer that integrates easily with the W5500io module? I’m not finding anything with a pinout that lines up well. I’m also trying to keep the height below about 14mm. Thanks, Scott

jaden · Answer

Hi what do you mean “Can’t find anything with a pinout that lines up well” ?

madsci77 · Answer

I mean every transformer I’ve found would require several signals to cross over other signals. They all have the center tap between the + and - sides, while the W5500-io has the two center tap signals together. Also all of the transformers seem to start with TD+ as pin 1, on the left edge of the part, while the left edge of the W5500-io has RX+ on the left. I’m not clear on whether the TX and RX sides of the transformer are interchangeable, but even if they are it means the CT traces have to pass under something.

jaden · Answer

Okay I understand. The RX and TX of the transformer can be changed and used interchangeably. And a transformer with a combined RCT/TCT can solve the problem. see the image below. image952×624 113 KB

madsci77 · Answer

In case anyone else comes across this thread and is looking for a suitable part, what I found was the Pulse HM0068ANLT. It has the chip side connections in exactly the right order.