Signal Integrity Issues and Printed Circuit Board Design

Chapter 15. Bypass Caps and Decoupling Systems

There are two views regarding bypass capacitor decoupling strategies today. They appear to be quite different on the surface, and they lead to some differences in results when taken to their logical conclusions. I tend to call them (a) the traditional approach, viewing bypass capacitors almost as little storage batteries (what I sometimes refer to as “little storage buckets of electrons”), and (b) the power system impedance approach, where the focus is on achieving a power distribution system impedance level below some target maximum at all relevant frequencies. We look at both of them here, and I’ll highlight the differences in conclusions between them.

Traditional Approach

Figure 15-1 shows a representative ...