FEDEVEL
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The Chosen One , 06-30-2025, 03:07 AM

Hi, two questions:

1. When adding RF edge plating in designs I have seen some designs will multiple sections seperated by the copper plating such as the board seen at the start of this video: https://www.youtube.com/watch?v=_pIr8wWoPEI. Question is, how is the grounding of all of these seperated and how is the ground of all them connected? In this design I want to seperate the IMU and GNSS GND's from everywhere else and seperate them with RF edge plating but I am not sure what the proper way to ground them is.

2. Can you please review the schematics attached and give me feedback on everything you see that seems wrong or that I should probably double check?

Robert Feranec , 06-30-2025, 05:38 AM

I don't do RF, but I don't think they are separated

QDrives , 06-30-2025, 12:08 PM

1) The board edge connection is connected to whatever you design it to connect to.
2) You cannot go from 3.3V to 3.3V with and linear regulator. The 1117 has avout 1.2V drop.
Set your grid to 100mil.
Have the netlabel always over the wire.
I2C SDA is a two way communication. Your opto coupling solution is not going to work.
SPI MISO direction is reverse compared to MOSI. Change your opto-coupler solution.
Splitting Gnd is useless if you power is simply from the same supply. Either use a DC-DC converter or do not 'split' Gnd.
If you want to reduce noise on you Gnd polygon, you can also just add a slit in the Gnd plane and only cross the signals when you continue the Gnd.

The Chosen One , 06-30-2025, 05:14 PM

What do you recommend I replace the optocoupler’s with? Or do you think I can just route the data lines as they are with no isolation in between

QDrives , 06-30-2025, 08:05 PM

If you just use a slit in the Gnd plane, you do not need opto-couplers.
You also want your LDO closer to the Gnd pass through connection.

The Chosen One , 06-30-2025, 08:36 PM

Is there any significant difference between routing those traces on top vs interior vs bottom signal layers? This is likely a 6 layer PCB btw.

The Chosen One , 06-30-2025, 08:37 PM

Also if parts of the PCB are completely sectioned off by the plating, what is the purpose of this if the grounds are not actually separated?

QDrives , 06-30-2025, 10:18 PM

Yes, traces on inner layers are shielded on top and bottom too.
Cross talk is also a bit different. Check the video with Eric Bogatin and Robert (yes, there are many)

QDrives , 06-30-2025, 10:23 PM

I assume you mean edge plating?
I do not know why you would do it. I usually place a guard ring around the board with vias every 5mm or so. I think that works just as well as edge plating, but without the additional cost.
Both 'force' you to keep noisy signals away from the board edge.

The Chosen One , 06-30-2025, 10:51 PM

I more so mean a design such as this one where you can see the designer has sectioned off parts with the metal plating. Is this just for aesthetics or is there an actual reason for why this is done?

Robert Feranec , 07-01-2025, 06:44 AM

this video may help you https://youtu.be/9lEtkysFGGg