On 12:27 AM 17/08/2004, Website Visitor said:
Is it possible to constrain auto routing of several point to point connections not only by geometric limits but also to electical requirements? The resistances of the connections are required to maintain specific ratios to each other.

Marko,

Which version of Protel are you using? Which auto-router are you using?

The later versions of Protel do allow you to set routing width based on characteristic impedance (takes into account layer stack-up and material thicknesses and dielectric constant). But this is not really what you want, I think.

You can set up matched length rules to ensure that certain nets are equal in length, and you can set up length rules to constrain a net to a specific length (with some margin). If you are talking about keeping only sub-sections of these nets equal in resistance then you will probably need to set up a few From-Tos and refer to these in the rules. If you are really wanting something that will allow narrowing of sections of the paired tracks, and then widening elsewhere to compensate to keep the overall From-To resistance equal, while giving some flexibility to the auto-router, then I can't think of a set of rules that would allow this in any Protel product.

If these connections are vital I think I would think about routing them manually and then locking them. If they are causing to much pain to the auto-router then study the routed result, make a twiddle and try again.

Bye for now,
Ian Wilson




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