I am currently utilizing a LiDAR sensor that only outputs single pair ethernet. I am using the SPEBlox (1GBASE-T1) board to convert to 4 pair 1000Base-T.
I plan for this signal to go the Gigablox Nano switch (where other 4 pair ethernet sensors connect to) to send to a backplane connector with only 1 ethernet port.
This is for an embedded system MCU and I am routing my own PCB to interface the sensors, power, ethernet signaling with the backplane connector that will connect to the MCU module.
My question is mostly regarding ground referencing on PCB with the transformer-less switch, and to see if the 1GBase-T1 SPE pair is compatible with the Gigablox Nano Switch itself or if I should convert it first with the SPEBlox board.
For ground reference, for the transformer-less switch, the ethernet signals have to be routed over the power ground signal going into the switch, and with capacitors instead of the magnetics, correct? I am attempting to find a solution to reduce noise from my power switching supply that is located on the PCB I am routing (but located away from the ethernet signals).
GigaBlox Nano is a standard gigabit ethernet switch, 1GBASE-T. You can connect one of the 1GBASE-T ports on GigaBlox Nano to the 1GBASE-T on SPEBlox, which will then be converted to a 1GBASE-T1 port.
In the case of transformerless ethernet on GigaBlox Nano, the ethernet traces are routed over the same ground that powers GigaBlox Nano. This is the case both before and after the capacitors.
If you are worried about power supply noise for a specific port, then it would advisable to add transformers back in to the ports in which you’re worried about. That will give you a second ground plane on the other side of the transformer.
One port that is connected to the MCU, and the other two are connected to 2 other sensors. I am hoping to get away without using magnetics as I have a relatively small space constraint, I will have to check back with the other engineers to see how bad the switching noise is. Now do the termination capacitors need to go between the Razor Connector and the picoblade connector with signals coming off the SPE converter board?
To clarify, the capacitors are not termination capacitors, they’re DC blocking series capacitors. In other words, they go between the two ethernet devices.
GigaBlox Nano already embeds series capacitors before it hits the RazorBeam connector, so you don’t need to add any.