Signal Integrity Issues and Printed Circuit Board Design

Chapter 17. Lossy Lines and Eye Diagrams

In days gone by we considered traces on PCBs to be (almost) perfect conductors. On rare occasions we considered their resistance and maybe propagation time, but usually not. Traces almost never contributed to signal integrity problems.

Then, as rise times shortened, we began to worry about signal reflections. In Chapter 10 we learned that signal integrity problems caused by reflections could be managed if we designed our traces to look like transmission lines and if we addressed questions like trace termination. Instead of traces resembling perfect conductors, traces resembled distributed networks of LC components. But if we could measure an effective input impedance whose value is given by Equation 10-1 ...