[Arm-netbook] HDMI High-Frequency Layout: Recommendations
richard.wilbur at gmail.com
Mon Aug 28 22:13:46 BST 2017
On Aug 22, 2017, at 08:13, Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:
> On Tue, Aug 22, 2017 at 2:43 PM, Richard Wilbur
> <richard.wilbur at gmail.com> wrote:
>> How much intra-pair skew do we incur at each of those bends?
> very little. it's a 45 degree bend in each case so.... can probably
> work out the maths... 15mil separation...
Between traces of the same differential pair (intra-pair) I would have expected 5mil separation.
I'm not entirely sure how PADS does the trace length calculation:
1. Is it measuring the inside edges of the differential pair traces? Then the intra-pair skew from one 45° corner would be 5mil.
2. Is it measuring the centers of the 5mil wide traces? If so I'd expect the intra-pair skew to be 10mil.
3. It may be measuring in a different way of which I'm not thinking.
> attached diagram is probably a lot easier. i also checked the
> Design Rules: board-to-everything-and-anything is set to 11.84 mil,
> everything-else-to-anything-else is set to 5mil.
> so in the attached diagram those traces i put right at the bottom
> will be overwritten by about... 1.2 mil to make up to the 11.84
> board-to-copper clearance.
Does that mean that flood fill will cover out from 13mil off the board edge (as noted in the diagram) up to the 11.84mil board-to-copper clearance?
> so, actually very simple. everything-to-everything-but-board: 5mil.
> board-to-everything: 11.84mil.
Simple is good--only as complicated as it needs to be.
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