On Sun, Dec 17, 2017 at 10:28 PM, Luke Kenneth Casson Leighton <[email protected]> wrote: > aw poop! i went to all the trouble of writing a parser for PADS :)
That is pretty cool. Now you have a way to algorithmically generate traces. I'm sorry we didn't need it, yet. >> Are there signals beneath the ESD components on layer 3 or 4? > > it seems i am sensible enough not to have done that :) > >> If not, >> we could put our ground reference planes on those layers under the ESD >> components which would move them both one layer deeper. (We already >> have several conveniently placed ground vias.) So it might be easier to just put a ground keepout on layer 2 under the ESD component on layer 1 and a corresponding ground fill on layer 3. Likewise a ground keepout on layer 5 under the ESD component(s) on layer 6 and a corresponding ground fill on layer 4. (The "otherwise" case below is given in case you feel more comfortable putting keepouts on layers 2 and 5 than changing layers 3 and 4.) >> Otherwise, I would >> just copy the lands for the ESD pads connected to the high-speed >> signals and put them as ground keepouts on the normal ground reference >> planes. > > makes sense to me > >> (In other words, only keep out the copper on the reference >> plane just under the signal path where it goes through a wide pad for >> the ESD component.) > > including the 5 mil track *between* the ESD pads, or excluding that? > so literally just the ESD pads, yeah? I was recommending just under the ESD pads specifically for the high-frequency differential signals. > >> Likewise with the connector, I would put a ground keep out under the >> lands on layer 2 (probably best to just draw a keepout under the whole >> connector on layer 2) > > including for the HSCL, HHPD and even the GND pads? of course there's > VIAs connecting the tracks in between the diff-pairs Wouldn't have to I suppose but the idea is to move the ground further away from the high-frequency pads to reduce the capacitive coupling thus increasing the impedance. Thus I think it's probably best to extend the layer 2 keepout under the whole connector. >> but allow layer 5 to provide a full ground >> shield. (Provided my assumption is correct that the connector is >> soldered on layer 1.) > > it is. Yay! _______________________________________________ arm-netbook mailing list [email protected] http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook Send large attachments to [email protected]
