[Arm-netbook] HDMI High-Frequency Layout: Recommendations--Taper

[Luke Kenneth Casson Leighton]

On Sun, Dec 24, 2017 at 10:29 PM, Richard Wilbur
<richard.wilbur at gmail.com> wrote:
> Thanks again for the pictures and the video.

 no problem

> Concerning the keepouts under the connector:
> 1.  At the north boundary I would pull the edge up a little further north away from the northwestern differential pair.

 oh!  ha, i just made it the opposite direction :)  reason: HHPD acts
(kinda) as a GND for that top (HTX2P) and when i did the flood-fill it
looked really weird.  i'm switching to a couple of different viewing
styles (one of them is actually the gerbers, there's an "X-Ray"
option.

 the top 2 VIAs right next to HTX2P are too far away, and the
15mil-to-GND-keepout condition makes things unbalanced.  see proposed
GREEN new via placements and YELLOW track to correct that.

 when i show X-ray-mode gerbers layers 1 & 2 i mark in yellow at top a
proposed modification, look good?  you can see to pin 4 there is that
GND via, the shape of the hole gets really weird / sharp edges there.

 also i'm aware that the layer 2 and 5 bottom-most
curved-shaped-keepout-holes are about 1 mil too far to the left, see
yellow (SE corner) where i'll move them both over.

> 2.  At the west boundary I see your point regarding layers 4 and 5.
>  Looks like you have made a good solution.
> I suppose you could add 5mil additional overlap.
> How much overlap does it currently have?

 currently arouuund 9mil roughly.

> How much opening from the edge of the keepout
> on layer 4 to the edge of the closest connector pads?

 around 4mil.  tracks are 5mil so can use that as a scale.

> I would vote to keep the layer 5 holes under the layer 6 ESD pads
> for the same reason we added them to layer 2 for the ESD pads on layer 1.

 yehyeh.

> Some of the adjustments on layer 6 might be taken care of by
> modifying the net groups to create an "HDMI High-Frequency"
> group which contains only the differential pairs {HTX2P, HTX2N, HTX1P,
> HTX1N, HTX0P, HTX0N, HTXCP, HTXCN}, apply the 15mil conditional
> clearance rule to that group.

 that's what's already done :)

 oh, except to VIAs i kept it at 5mil, now i remember.   15 mil to
landing pads, 15 mil to tracks, 5mil to VIAs i think this was because
i didn't want the holes made by VIAs to be too large.  what you think?
 make them 15mil too?

l.
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