Meaning
Timing deviations of a periodic signal from its ideal occurrences represent a primary cause of high-speed communication failures on printed circuit boards. When clock jitter exceeds the setup and hold thresholds of a receiving flip-flop, data bit corruption occurs. This instability limits the maximum achievable baud rate of serial interfaces such as SPI or high-speed serial links.
Physical Source
Trace routing near switching power supplies or high-frequency digital lines induces electromagnetic interference that introduces phase deviations. Poor board-level power distribution networks can also cause fluctuating voltage levels at the clock generator pins, which directly translates to period variations. Designers must mitigate these effects through careful layout practices.
System Performance
High deviations in timing degrade the signal-to-noise ratio of analog-to-digital converters, limiting the precision of sensor readings. In high-speed data links, this degradation shows up as an increased bit error rate that forces packet retransmissions. This error rate reduces the effective throughput of the communication channel and increases power consumption due to continuous active processing.
When the system operates under extreme temperature variations, these phase deviations can compound, causing the link to fail completely if the margins are too narrow.
Mitigation Strategy
Placing decoupling capacitors close to the clock generator minimizes supply-induced phase noise. Using differential clock distribution circuits provides high immunity to common-mode noise, which helps maintain a stable reference timing across the entire board. In demanding applications, dedicated low-noise phase-locked loops can filter out high-frequency phase variations before the signal reaches critical components.
