FEDEVEL
Platform forum

mostafa222 , 03-01-2017, 01:06 AM

Hi. I set my diffrential net as DIF100 class like below picture. But when i want to set rules for this class, in rules window, in "differential pair routing" object, i choose "diff pair class", but in the list, i can't see my DIF100 class(picture 2). What is the reason?
I use altium 17.08

mairomaster , 03-01-2017, 01:47 AM

Net class class and differential pair class are two different things. The way you do it in schematics is right, but it only includes the diff pairs in a net class called DIFF100. After that in the PCB you have to create a diff pair class from Design - Classes... - Differential Pair Classes, and include all differential pairs in it. Robert explains that in one of the Advanced PCB Layout videos, if you have the course. It's a common mistake and it's not very intuitive.

I was thinking about exactly the same thing this morning and how easy is to forget to add the pairs to a differential pair class. I have the idea to add a differential pair class parameter to the diff pair symbol in schematics, so that the pairs are added to a diff pair class automatically when importing in the PCB, the way it is done with the normal net class. I will try if it works and post here.

EDIT: The video from Robert:

mostafa222 , 03-01-2017, 01:49 AM

Thanks so much

mairomaster , 03-01-2017, 03:17 AM

Unfortunately I couldn't find a way to add the differential pair classes to schematics. Also the option to import such into the PCB is not available in the ECO list, so I guess it's not possible.