Best posts made by thomasderbauer

Hi Onioneers!
I am building a project with stacked PCB's. The first PCB contains the Omega2S+ and a CP2102 for Serial Connection. Second PCB contains RJ45, PoE and PSU Components.
When Connecting only the second PCB to my Switch with PoE the 3V3 LED lights up and I can see in my switch that PoE is detected correctly and it's pulling about 0.9W.
I then combined the two PCB's together and used USB to my PC to create a Serial Connection (No Ethernet connected). In this case the 5V of the USB goes to the 5V Rail on the PSU PCB and gets regulated down to 3V3 to supply the omega.
I then connected Ethernet with a non PoE port. It gets detected and I could ssh into the omega and worked for 20 minutes on it. I then unplugged the USB Cable and plugged the Ethernet into a PoE Port. This led to the board shorting all components. I had to replace CP2101, Omega and both Voltage Regulators. What I'm not sure is why this doesn't happen on the USB but with the PoE.
I attached the two schematics. The boards are connected via the 10pin connector.
Any Hint or Idea what could cause this would be greatly appreciated.