• Highest Frequency of concern IS NOT the Clock.
• IT IS Frequency of the High Harmonics necessary to create the Fast Rising Signals,
called : Maximum Pulse Frequency.
• F(freq-GHz) = .35 / Tr(rise time-nSec*)
• (Tr = 10-90% (Typical))
• (Tf = 10-90% (Typical))
• Emission Bandwidth is from Clock to Maximum Pulse Frequency.
Signal Integrity Basics
• Signal Integrity is a field of study between digital design and analog circuit theory.
• It ' s about ringing,
• ground bounce,
• power supply noise.
• It's all about how to build fast digital hardware that really works.
• It's about practical, real-world solutions to high-speed design problems.
• Signal Integrity is a deterministic, predictable field of study (a "hard science").
• Signal integrity specialists make frequent use of the fact that most signal integrity
problems are easily observed.
• A good simulation, can usually put to rest any question about the efficacy
of a particular solution.
• Signal Integrity didn't always matter -
• In the golden years of digital computing (1970-1990),
gates switched so slowly that,
digital signals actually looked like ones and zeros.
• Unfortunately, those days are gone.
• At today's speeds even the simple, passive elements of a high-speed design -
the wires, PC boards, connectors, and chip packages -
can make up a significant part of the overall signal delay.
• These elements can cause glitches, resets, logic errors, and other problems.
• A greater percentage of PCB traces in new designs will require terminators.
• The exact delay of individual PCB traces will become more and more important.