Decoupling Capacitors; Stitching Capacitors Should Be Close To Traces; Decoupling Capacitors Locations - Intel Quark SoC X1000 Design Manual

Figure 65.

Stitching Capacitors Should be Close to Traces

17.4.4.2

Decoupling Capacitors

Decoupling capacitors are used to mitigate the noise on power rails or planes. Noise
sources on power rails or planes are mainly from voltage regulators and IC chipsets.
Decoupling capacitors connected between power and ground could create shorter
return paths for the noise currents. In order to minimize return paths, place capacitors
as close as possible to noise sources.
In "Decoupling Capacitors
capacitor is placed closest to the IC and the wider power rail has lower inductance.
"Decoupling Capacitors with Vias"
the traces are decoupled prior to being routed. Locations "a" and "b" are acceptable.
Location "c" is not acceptable since the via is placed before the bypass capacitor.
Location "d" is poor since two capacitors are tied to one via (this is not a good
practice). Location "e" is poor since two capacitors are tied to one via and the via is
before the capacitor (the via should be on the other side of each capacitor).
Figure 66.

Decoupling Capacitors Locations

®
Intel Quark™ SoC X1000
PDG
118
®
Intel Quark™ SoC X1000—Electromagnetic Interference
Locations", option "b" is the best because the decoupling
shows the via locations. Vias should be placed where
June 2014
Order Number: 330258-002US