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On Wed, Aug 30, 2017 at 1:54 AM, Richard Wilbur richard.wilbur@gmail.com wrote:
Luke,
Thank you ever so much for the clarification regarding perspective.
Comments inline below.
On Aug 22, 2017, at 12:25, Luke Kenneth Casson Leighton lkcl@lkcl.net wrote:
okaay, wiggle-progress... 1st image is left end, i think CX and TX0 i can shorten even more, there's definitely plenty of space there, big gap.
Shortening CX and TX0 is fine but I would cramp any of the clearances to make it happen.
there aren't any!! the GND separation vias see to that (attached). no there's not enough room to move those GND vias *in between* the VIAs, they need to be below, unfortunately. that means the diffpairs need to curve _round_ them (to the SW slightly). oops.
actually it just occurred to me that i could move the HXT?P vias over by another.... 10-15 mil or so, which would mean that the corresponding HXT?N traces would be able to go straight (directly south) instead of SW, S then SE.
phrrrrddhh :)
On the other hand, if you were to put them into a 45° bend from south to southeast a little sooner, we would probably have enough room to adjust the ground shield trace on the southwest and west to abide by our 15mil differential trace to "anything not in the same pair" clearance (specifically to HTXCN).
well, unless i add a flood-exclusion zone (thoughts on that?) anything W or SW of HTXCN is going to get flood-filled with GND.
or... i _could_ just put in a copper-to-diffpair Design Rule of "15 mil" clearance - that would keep the flood-fill away.
anyway those wiggles are done by hand, some of them aren't pretty but in mil those traces are now nearly all to within 0.01 mil. i cheat a little and have made some of the corners in places a very very tiny arc, where you get better fine-grain control over the amount it takes off.
Well done.
... i'm getting used to it....
HTXCN just before the diff-pair vias at the end i'm a little concerned about, it looks a bit too... sharp-angled to make me feel totally comfortable... not a lot of space... i tried a single wiggle and it went too far away from HTXCP for me to feel happy about it.... put in two much smaller wiggles instead...
GND i'll remove as the absolute last thing.
Sounds great. Only really want to remove the ground traces that can't comply with the 15mil clearance between differential pair and anything not in the same pair.
marked in this image, i was planning to remove the GND traces that are marked with red dots.... but only after all's done because currently they help keep the inter-pair separation.
does that sound sensible?
l.
