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Karan paliwal , 12-31-2025, 03:37 AM

I am setting a 90-ohm USB differential impedance profile in Altium Designer using the Layer Stack Manager, where I can see the option to add an impedance profile. My question is: How can I control and design vias for a USB differential pair when the signal changes layers? Is there a way in Altium to include vias in the impedance profile, or should via impedance be handled separately? What are the best practices for managing via geometry (drill, pad size, antipad) to maintain USB impedance consistency? Any guidance or recommended workflow in Altium for via impedance control

QDrives , 12-31-2025, 03:56 PM

First: Use Shift-Enter to get a new line.

"*How can I control and design vias for a USB differential pair when the signal changes layers?*"
Not sure what you mean. Vias have a (finished) hole size and a pad size(s). Either in a template or limits.

"*Is there a way in Altium to include vias in the impedance profile, or should via impedance be handled separately?*"
No. The 'impedance' of the via depends more than the via alone. Your signal via may require a return via too. A via **will** cause a impedance discontinuity. It is up to you which 'form' you like best. Look at the videos with Yuriy Shlepnev, like this one https://www.youtube.com/watch?v=yQIBS5xwvVQ

"*What are the best practices for managing via geometry (drill, pad size, antipad) to maintain USB impedance consistency?*"
Someone analyzed that a via needs a drill of 0.2mm to be the best result. Then you need a minimum annular ring. You may want your anti-pad as big as possible to reduce cross talk, yet small for the return via(s).

"*Any guidance or recommended workflow in Altium for via impedance control *"
All you mention is USB. Not which speed / frequency you need. For the highest speeds (>=20Gbps) you may want to analyse your design using tools like Simbeor.

Karan paliwal , 01-02-2026, 04:14 PM

thanku