文档介绍：TN-00-06
BYPASS CAPACITOR SELECTION
TECHNICAL BYPASS CAPACITOR
NOTE SELECTION FOR HIGH-
SPEED DESIGNS
This article was originally published in 1996. and resistance (R1, Rg2, L2, Lg2 in Figure 1) so that
transient currents flowing across the power bus do not
INTRODUCTION cause excessive noise at the power and ground pins of
In order to guarantee better performance from high- the IC. Therefore, the bypass capacitor should have low
speed digital integrated circuits (ICs), manufacturers effective series resistance (ESR) and series inductance
are tightening power supply noise margins. With lower while having a large enough capacitance value to
power supply noise margins, the designer needs to pay supply current to the IC during switching.
closer attention to local bypass capacitor selection. Several factors need to be considered when selecting
As bus speeds increase and switching times decrease, local bypass capacitors. These factors include selecting
proper selection of local bypass capacitors for high- the proper capacitor value, dielectric material, geom-
speed digital ICs is ing plex. etry and the location of the capacitor in relation to the
With wider parts ing prevalent in cache sub- IC. Careful observance of fundamental principles will
systems, the amount of current required from the determine how well the capacitor can suppress switch-
bypass capacitor