klokjitter

Klokjitter, or clock jitter, refers to the deviation of clock edge timing from an ideal periodically repeating signal. It describes short-term timing variations of clock transitions and can be further described as phase, period, or cycle-to-cycle jitter. In practice, jitter is often divided into deterministic and random components, and may include periodic disturbances.

Jitter arises from noise and disturbances in the clock source (such as oscillators and phase-locked loops), power supply fluctuations, crosstalk, temperature changes, and data-dependent switching noise from digital circuitry. It is typically quantified by RMS jitter or peak-to-peak jitter, and is sometimes expressed through phase-noise measurements. Measurements are performed with high-speed oscilloscopes, specialized jitter analyzers, or phase-noise analyzers, and are often considered within a system’s jitter budget.

Excessive jitter reduces timing precision and can cause bit errors in high-speed serial links, sampling errors in analog-to-digital conversions, and misalignment in synchronous buses, potentially degrading overall system performance and quality.

Mitigation strategies include selecting low-jitter oscillators and PLLs, using carefully designed clock distribution networks with low skew, and improving PCB layout, grounding, and power regulation. Additional techniques include clock-data recovery and deskewing in receivers, as well as comprehensive jitter budgeting to allocate acceptable jitter levels across subsystems.

Klokjitter is a central consideration in digital communication and timing-sensitive applications such as PCIe, USB, Ethernet, and memory interfaces, where tolerance and specifications for jitter dictate reliable operation.