Signal Integrity Measurement Analysis
White Paper
Signal integrity (SI) addresses two key aspects of high-speed digital design: signal timing and quality. SI analysis ensures that signals reach their destination in good condition. For example, a system with good signal integrity has data that arrives early enough to meet timing requirements and to avoid false clocking (where a clock crosses a logic threshold more than once during a transition).
In a system, signals travel through various kinds of interconnections. For example, from chip to package, package to board trace, and trace to high-speed connectors. Signal integrity problems arise from the physical nature of the interconnecting wires. Unlike a connection line drawn on a schematic, a real wire has resistance, capacitance to ground and to other wires, and inductance. At higher frequencies, capacitance and inductance cause the wire to act as a transmission line. The resulting antenna effects result in crosstalk and electromagnetic interference (EMI).
Sufficiently significant signal-integrity problems cause systems to fail or work only intermittently, producing “bad” data. It is crucial to find signal integrity problems early in a design cycle. Intermittent failures are difficult to debug on prototypes.