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On Fri, Dec 22, 2017 at 9:37 PM, Richard Wilbur richard.wilbur@gmail.com wrote:
On Dec 22, 2017, at 07:51, Luke Kenneth Casson Leighton lkcl@lkcl.net wrote:
On Fri, Dec 22, 2017 at 8:54 AM, Luke Kenneth Casson Leighton lkcl@lkcl.net wrote:
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this is a pain! i might see if i can set a clearance to GND on individual tracks / connections as opposed to NETs.
ok that worked. just uploading a video here:
turns out that there's a feature i'd not used before, called "conditional rules". you can specify that *if* GND meets HDMI Group, clearance rules shall be different. ordinarily you have to forcibly set the *entire* GND plane to specific clearances (to ALL objects), or the *entire* HDMI group to specific clearances (to ALL objects)... this "conditional" rule does the trick.
Nice work! That certainly simplifies things!
tell me about it. and also makes for much cleaner / accurate separation.
I believe that the right thing is to not extend the layer 5 ground keepout under the differential nets on their way out to the connector because it is the ground plane for layer 6.
that makes sense.
The reason for dropping the ground plane under the connector pins (layer 1) from layer 2 to layer 5 is that the pins are so close to each other.
yyeahhh but so are the pins on the bottom layer ESD... which are covered by the layer 5 GND keepout hole... it was under the connector i was concerned about, with the VIAs on pins 4 10 and 16 (right-hand row of 9) being guard VIAs that are within 5mil of HTX1P/N and THXCP/N...
But we are still interested in the shielding effect of ground plane below the high-frequency signals (on the differential pairs) on layer 1 and between the signals on layer 1 and those sneaking under on layer 6.
yehyeh.
That's my reason for keeping layer 5 ground fill everywhere except under the layer 6 high-frequency pads of the ESD (where he drop to ground on layer 4).
yehyeh, with you.
l.