--- crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
On Fri, Dec 22, 2017 at 9:37 PM, Richard Wilbur <[email protected]> wrote: > On Dec 22, 2017, at 07:51, Luke Kenneth Casson Leighton <[email protected]> wrote: >> On Fri, Dec 22, 2017 at 8:54 AM, Luke Kenneth Casson Leighton >> <[email protected]> wrote: > […] >>> 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: >> >> https://youtu.be/LfQc89CS4m0 >> >> 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. _______________________________________________ arm-netbook mailing list [email protected] http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook Send large attachments to [email protected]
