TABLE OF CONTENTS Here's what you're going to see in this chapter:
Worst kind of circuits for noise problems
Causes of zaps, spikes, and krrrr sounds
Key analogy to remind you of common sense solutions
Why you might suggest a certain library
How to create a Wall of Death
Or two Walls of Death, one for you
Timing solution
Location, location, location
to make a 360 shield
Running two lines instead of one
Placing a capacitor in the neighborhood
Stacking your power rails
Unwanted secret signals created by your main signals
Noise in an integrated circuit can be a pretty big problem, particularly when you have very sensitive circuitry that is trying to pick up some very low value signals, located next to noisy circuitry that's doing all sorts of computations, control logic and noisy switching. We have to pay very special attention to our layout and our floorplan. We need to understand where the signals are wiring to and from. We need to be real careful.
Noise becomes very painful to deal with, particularly in mixed signal chips. Mixed signal circuitry has the most problems with noise because analog and digital circuits operate at very different noise levels.
In a digital circuit, you have two transistors that connect across a power rail. Every time they open or close, there is a possibility that for a very small amount of time both those...
