On Thu, Aug 10, 2017 at 9:01 AM, [email protected] <[email protected]> wrote: > 2017-08-09 15:23 GMT+02:00 Luke Kenneth Casson Leighton <[email protected]>: >> next set... >> > GND shielding parallel to the differentials is interrupted quite > often.
because there's simply not enough space to do otherwise. if i could move the entire CPU and RAM up another 0.5mm it would be doable. but then i would have to re-route 12 signals which go around the top area of the board and that's (a) risky and (b) not enough space to do it. > Those GND tracks act as shields, for emission and reception. > I'd try to put as much parallel GND as possible. > > And trace the parallel GND around the via's, see attachment. ah, got it - thanks for the tip, i thought i'd done that on all diffpairs, but i missed one. good call. yes there's only one, because the layer 1 and layer 6 will be flood-filled and that will fill the areas that "appear" to be missed. > Make sure the'res as much solid GND on the layer above and below the > traces, again shielding. these are layer 1 and layer 6, and layer 2 and 5 are solid GND. > Also I'd personally not use curved wriggles. HF signals travel in a > straight direction. With curves they start diffracting and start > bouncing cross each other and might start to radiate or echo back. mmmmm.... *stress*! anyone else feel the curves are "Bad"? > But > I see that the community is divided on that stance. > > If tight for space you can use 90% corners with a chamfered outer > edge. I suppose the chamfer acts like a mirror. i'd *really* prefer not to do that :) > https://www.maximintegrated.com/en/app-notes/index.mvp/id/5100 > Figure 6 wow that's pretty bad-ass. _______________________________________________ arm-netbook mailing list [email protected] http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook Send large attachments to [email protected]
