FEDEVEL
Platform forum

, 08-03-2024, 11:24 AM

Hello,
I'd like to ask.. I am designing USB-A 3.0 extension board and i am quite confised how to connect shield between two connectors. Look at the picture. Is this good? Just connect shield pads together with trace on bottom layer? The board is 4layer (SIG, GND, PWR5V, GND+GNDshield?)

Thank you
Regads, Martin

QDrives , 08-03-2024, 12:32 PM

I would use the Gnd as shield too. Shield is the reference for the signals in cable too, so why not on the board.

, 08-03-2024, 12:47 PM

Hi Qdrives, sure but on the second board (USB hub) where I want ho plug this "extension board" I have separated GNDshield through RC components according to microchip recommendation.

QDrives , 08-03-2024, 08:44 PM

That is another board, so other 'rules'.
One other tip, place the length matching meander closer to the length mismatch. In this case close to J3.

, 08-04-2024, 08:14 AM

thanks for that tip about length matching. And how to deal with that GNDshield? What would be the best solution? I got idea that if change stackup to SIG, GND, PWR5V, GNDshield plane.

, 08-04-2024, 08:42 AM

Also, will GND via fence around board edge improve something? Whether to add it.

QDrives , 08-04-2024, 12:17 PM

You want to separate the Gnd in the 'signal' from the shield?
On this board, that is just an extension of a USB connector, I would then go for Shield - Sig - Shield - Power (Vbus and USB Gnd, pin 4+7)

, 08-04-2024, 01:45 PM

You want to separate the Gnd in the 'signal' from the shield? = Yes, that was my idea..

, 08-04-2024, 01:46 PM

Your idea about new stackup setup sounds good. Thanks

QDrives , 08-04-2024, 07:00 PM

There may be another 'stack-up'.
Have top and bottom as the shield.
Inner layer 2 has USB-Gnd as polygon.
Route Vbus on signal layer (routed power).
This makes the signals and Vbus reference both shield and USB-Gnd.
You can via stich the perimeter of the board to fully shield the signals.

So simplistic stack-up: shield - sig+power - USB-Gnd - Shield

, 08-05-2024, 07:14 AM

Thank you for advices. I try both combination of stackup and I will send it to manufacture.