kicad-developers team mailing list archive

[Jon Evans <jon@xxxxxxxxxxxxx>]

Agreed. Diff pairs should have an associated clearance rule to other
objects and it has nothing to do with the gap.

One place where the gap should be used is in manual tuning of the pair. If
I route a pair and end it on a component that necessarily has non-symmetric
pad fanout, I might want to move one of the diff pair tracks and not the
other. The gap is then the clearance used to the other track when
considering it for PnS.

On Tue, Sep 18, 2018, 07:20 Jeff Young <jeff@xxxxxxxxx> wrote:

> When calculating obstacles we currently use the diff-pair gap as a
> clearance between a diff-pair trace and a diff-pair pad.
>
> I’m pretty sure that’s wrong.  I’m just not sure how wrong.
>
> I suspect the diff-pair gap shouldn’t be used as a clearance *at all*.
> It’s the gap between the traces, not a clearance.
>
> But maybe we should consider it a clearance between two *tracks* of a
> diff-pair.  This would allow you to manually route each wire.  But if you
> do that, should we consider it a diff-pair or not?  (Even if we use the gap
> as a clearance, it’s only going to enforce minimum distance; it won’t keep
> the tracks gap-width apart.  And I imagine you won’t be able to tune it.
> So I’m not sure it’s really a diff-pair.)
>
> Thoughts?
>
> Cheers,
> Jeff.
>
> https://bugs.launchpad.net/kicad/+bug/1789690
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