EP2S180F1020C4 Datasheet, PDF (748/768 Pages) Altera Corporation – Stratix II Device Handbook, Volume 1

Routing Schemes for Minimizing Crosstalk & Maintaining Signal Integrity
Figure 11–11. Dual- and Single-Stripline Layouts
Single-Stripline Layout
W
Ground
Dual-Stripline Layout
W
Trace
H
Dielectric
Material
Ground
Take the following actions to reduce crosstalk in either microstrip or
stripline layouts:
■ Widen spacing between signal lines as much as routing restrictions
will allow. Try not to bring traces closer than three times the dielectric
height.
■ Design the transmission line so that the conductor is as close to the
ground plane as possible. This technique will couple the
transmission line tightly to the ground plane and help decouple it
from adjacent signals.
■ Use differential routing techniques where possible, especially for
critical nets (i.e., match the lengths as well as the turns that each trace
goes through).
■ If there is significant coupling, route single-ended signals on
different layers orthogonal to each other.
■ Minimize parallel run lengths between single-ended signals. Route
with short parallel sections and minimize long, coupled sections
between nets.
Crosstalk also increases when two or more single-ended traces run
parallel and are not spaced far enough apart. The distance between the
centers of two adjacent traces should be at least four times the trace width,
as shown in Figure 11–12. To improve design performance, lower the
distance between the trace and the ground plane to under 10 mils without
changing the separation between the two traces.
11–12
Stratix II Device Handbook, Volume 2
Altera Corporation
May 2007