December 6, 2010 -- Printed circuit boards (PCBs) are by far the most common method of assembling modern electronic circuits. Composed of a sandwich of insulating layer (or layers) and one or more copper conductor patterns, they can introduce various forms of errors into a circuit, particularly if the circuit is operating at either high precision or high speed. PCBs, then, act as "unseen" components wherever they are used in precision circuit designs.
Since embedded designers don't always consider the PCB electrical characteristics as additional components of their circuits, overall performance can easily end up worse than predicted. This general topic, manifested in many forms, is the focus of this series of articles.
PCB effects that are harmful to precision circuit performance include leakage resistances; spurious voltage drops in trace foils, vias, and ground planes; the in?uence of stray capacitance, dielectric absorption (DA), and the related "hook." In addition, the tendency of PCBs to absorb atmospheric moisture, hygroscopicity, means that changes in humidity often cause the contributions of some parasitic effects to vary from day to day.
In general, PCB effects can be divided into two broad categories: those that most noticeably affect the static or dc operation of the circuit and those that most noticeably affect dynamic or AC circuit operation.
By Walt Kester.
In this three part series, Walt Kester provides a compendium of tips and hints that will help embedded systems developers speed the design of the printed circuit boards upon which their designs are based.
This brief introduction has been excerpted from the original copyrighted article.
View the entire article on the EE Times Embedded website.
