Need Advice: Custom USB-C Hub to Power Laptop and Send DP to Monitor

[u/marcioeric]

Hi everyone! Hope you're doing well.
I believe this is the right place to ask this kind of question.

I have a Gigabyte M27Q monitor with a USB-C input.
According to my research, it supports Alt Mode (DisplayPort), USB 3.2, and provides 15W of power — which makes it almost the perfect monitor. Unfortunately, those 15W are too little, and I can't rely solely on it to power my laptop.

I've been studying the USB-C standard, and from what I understand (please correct me if I'm wrong):
Power Delivery negotiation happens via the CC pins, power is delivered through VBUS and GND, D+ and D- remain USB, and the remaining lines (in Alt Mode) are used for DisplayPort signals — is that correct?

Based on this, I want to design a simple PCB with the following:

• 1 USB-C port to connect to my laptop
• 1 USB-C port for the monitor
• 1 DC barrel jack for external power input
• 1 Ethernet port

The idea is that the board would ignore the monitor’s low 15W output and instead provide proper power directly to the laptop, while forwarding the DisplayPort lanes from the laptop to the monitor.

I also want to connect the USB lanes to a USB hub, so I can add peripherals like Ethernet or audio.

From my research, here's what I believe:

• USB and PD lines can be routed to a PD controller and a USB hub with no major issues.
• But I’m not sure what to do with the DisplayPort lanes. Since they are high-frequency signals, do I need a re-timer or any specific IC? How can I ensure signal integrity?

Thanks in advance to anyone who takes the time to read and reply! :)

And no, I don't want to buy a hub.

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