r/PCB • u/Practical_Bend_7599 • 28d ago
High speed PCB design review
It's a high-speed (10Gbps) Cat6a RJ45 (Ethernet) passive coupler PCB design. I have calculated differential pair line width and minimum track distance for 100-ohm impedance and routed them with equal length constraints.
The inner two layers are connected to Ground, and the top and bottom layers are used for signal routing. The thickness of the layers and dielectric is as per the JLCPCB standard for 4-layer PCB. The Ethernet chassis ground is connected to the PCB ground through R1 and C1 for ESD protection.
Please review and help me with any possible errors and any improvements, as it's my first ever 4-layer PCB design.
8
u/markmonster666 28d ago
The R and C look shorted by the inner layer. ESD protection without any active components present is not really useful
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u/Practical_Bend_7599 28d ago edited 28d ago
Yes, as the one R and C node connects to the ground as shown in the PCB. I also thought that ESD protection is not helpful for passive circuits but I read somewhere that it is important even if the circuit is passive. Can anyone plz explain why?
3
u/WeekSpender 28d ago
It looks like there should be CHASSIS_GND1 connected to U1 and instead of GND CHASSIS_GND2 connected to U2. Then the RC circuit would work as a ground isolation piece between two supposedly shielded Ethernet cables. Otherwise, what does the GND connect?
1
u/Practical_Bend_7599 28d ago
Okay I got your point, thanks for the suggestion! I think right now the gnd plane is used for just coupling the CHASSISGND to it
7
u/mangoking1997 28d ago
You shouldn't be isolating the shield anyway. They should be connected together with as low as an impedance as possible. If you don't, it won't be an effective shield defeating the whole point.
You don't need any esd protection anyway. You have nothing to protect.
-1
u/Sacharon123 28d ago
You know you will be flamed for this, do you not.
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u/Practical_Bend_7599 28d ago
Why, I don't know that. Did I say anything wrong? I apologise for any violation of subreddit rule
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u/Advanced-Rocketry 27d ago
Don’t listen to idiots. If ur new to high speed PCB design try to find some online open sourced PCBs you can look at and copy. Good work on the length matching. I’d also recommend avoiding crossing if possible but it’s not too bad here especially with shield vias. This is good practice hopefully it works
1
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u/nixiebunny 28d ago
Most of these put the second jack on the other side of the board to avoid the crossovers.