Clock generators and synthesizers are integral components of many electrical systems. They produce clean output clocks with precise frequencies. The clock provides a time reference for a system. This enables events to occur synchronously and at predictable intervals, which is critical for many system functions, such as data transfer. The frequency of the generated clock may be fixed, or adjustable by an analog voltage or digital control word. The term ‘synthesizer’ is often used for devices that can produce multiple clock frequencies over a specified range with a known reference clock. At the core of the clock generator is an oscillator that resonates when energy is supplied to it. The oscillator may be mechanical such as a crystal oscillator, or electrical such as an inductor-capacitor (LC) tank resonator. The output of the oscillator is stabilized with feedback and amplified in order to improve performance and signal strength. The quality of a clock signal is typically characterized by the amount of jitter, or timing uncertainty, that it contains. Phase noise is often used to quantify clock uncertainty in the frequency domain. Be cautious when comparing the performance of clock generators and synthesizers, as jitter and phase noise can be expressed in a multitude of ways. Lire la suite Voir moins