I would like -- probably quite stupidly -- to ask if anyone has built a
working Ethernet device using only a dual-layer board. All the appnotes
seem to assume you have multiple power and ground planes, which pretty
much assumes a four-layer board or more. I'm assuming an integrated
MAC-PHY chip and a magjack here, so at least the number of spans on the
board is only one, as opposed to three.
It would be good to hear how critical placement is and if there is any
particularly good/bad ways to do it.
Additionally, most modern silicon is available only in very small
packages (typically 0.5 mm TQFP and so on.) Anyone has any suggestion
for how best to deal with the change from an inch-based grid (for the
larger components) to a metric grid (for the small ones)? This has to
fit into a Eurocard chassis, completely with a B/AB connector, so using
an all-metric grid is unfortunately not possible (although "everything
except the connector is on a metric grid", of course, is.)