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Differential Pair routes with No Gap

Korey

Hi,

I'm using OrCAD PCB Designer and have created differential pairs. When I manually route the pair, the gap between traces is always zero no matter what I set the gap to in the contraints manager. I'm fairly new to this tool so I'm getting a littel frustrated why it does this. I even found another posting that some provided a .brd design with a diff pair and its own CM settings. When I deleted the traces to then reroute them, I found the same problem, the trace gap went to zero! Is this a license limitation or am I missing something? I've created CSet spacing parameters in the CM.

Thanks for any help that someone might be able to provide.

 -KC 

  • steve

     Differential Pair Spacing is controlled in the Physcial/Electrcial domain. Look at Primary Gap and Mine Line Spacing. There is a really useful PDF App note on this :- http://www.parallel-systems.co.uk/images/PDF/diffpairs_definition.pdf

  • Korey

    Hi Steve,

     Thanks for your response and the PDF referance. What I'm finding is that the "Min Line Spacing" in the CM is grayed out. I don't understand why this is and I assume that this is the issue? I'm using OrCAD PCB Designer Professional... could this be a limitation issue that only Allegro has? I took another board design that had some routed Differential Pairs and when I ripped them up and tried to route them, the same thing happes and the routes have not spacing and are next to each other (Head Banging).

    If this is a limitation issue I guess I"m stuck but if there is a way to change the CM so that the Min Line Spacing isn't grayed out, that would be great. All other features for DP seem to be functional so I'm confused and will be shocked if a Pro version has this limitation. I tried to use the command diffp_line_space but it dont recognize it.

     Thanks for any help I can get.

     -KC 

  • oldmouldy

    Can you zip and post your BRD file? The Min Line Spacing is editible for Constraint Sets and Nets, it is "greyed out" for the Design (Dsn) entry in CM.

  • fxffxf

    If a field in constraint manager is grey, try doubling clicking on the cell. Constraint manager should open a popup that will indicate why you cannot change the field.

  • Korey
    fxffxf said:

    If a field in constraint manager is grey, try doubling clicking on the cell. Constraint manager should open a popup that will indicate why you cannot change the field.

    When I double click on the "Grayed" Min Line Spacing the dialog box says "DIFFP_MIN_SPACE does not apply to Designs"

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