Diff pairs around vias?

[Robert.Adams]

Hello all,

I'm trying to use differential pairs in Altium (v 15.1.15) for the first time and I'm having a hard time getting them to get past a via.  I've attached an example image below.  I've tried the rule wizard in the differential pair pane to set max gap high (150 mils) and also tried setting the max uncoupled length very high (> 1000 mil). 

I'm sure I'm just missing something simple, like the rule is not applied to my differential pair somehow but I can't figure it out with the Altium docs.  Can anyone help identify the problem with this?

[T3sl4co1l]

Try routing each one separately, then doing the majority span with differential routing, then clean up again with single mode, or by moving traces.

I view combo modes (differential, multi/bus routing) as tools to speed up connectivity -- a quick and dirty method, to be cleaned up later.

Tim

[DerekG]

I'm sure I'm just missing something simple, like the rule is not applied to my differential pair somehow but I can't figure it out with the Altium docs.  Can anyone help identify the problem with this?

When activating differential pairs, Altium still uses all its autorouting algorithms. One of these algorithms is "loop removal". If you look at the first two track segments (of each differential pair) you can see that a loop will be formed when the track is forced around each side of the via. This then clashes with the "loop removal" algorithm.

One fix would be to manually place the first track segment (of each differential pair) directly southwards from the via (which by the way will shorten each route which is what you want).

Then can then follow T3sl4co1l advice above to complete the differential pair route.