IDT晶体振荡器的抖动第2篇

Jitter in Oscillators

Jitter in oscillators should arise only from random sources if they are correctly designed and the output frequency matches the natural resonant frequency of the crystal. The random jitter in the oscillators should be sufficiently small as to be measured in picoseconds. This should be the case for all oscillators even for those whose output is a squarewave signal derived from the sine-wave output of the crystal oscillator.

The jitter in programmable crystal oscillators is generally larger due to the way in which their output frequency is generated. They usually use a phase locked loop (PLL) method of frequency generation and this can increase their susceptibility to jitter, usually in the order of 100ps rms. It is useful to consider the jitter that may be induced into the system from external systems. If a low jitter signal is essential to the workings of the system then choosing a component with low jitter values isn’t enough and a decision should be made to design a circuit that minimises jitter. For example shielding the component and circuitry from interference may be sufficient or placing a simple RC-filter in the supply line may help attenuate all high voltage ripples from the power supply. The output signal from the oscillator may be pure and clean however the circuit in which it lies may be easily susceptible to noise and jitter.

由于大多数数字系统都依赖于通用时钟总线关心电路是否能承受任何轻微的时钟脉冲定时的变化。

Jitter Effects

As most digital systems rely on a universal clock bus, we are concerned in whether a circuit can tolerate any slight changes in clock pulse timing.

在数字通信系统中，编码数据是通常通过长距离发送，然后进行解码一旦收到。然而，需要有一个共同的时钟，以允许对脉冲进行解码，并且如果时钟中的任何一个受到抖动的影响，数据可能会丢失从源头上讲诚信。同样值得考虑的是应用程序，然后选择合适的晶体振荡器。

In digital communication systems, the encoded data is usually sent over long distances and it is then decoded once received. However there needs to be a common clock to allow for the pulse to be decoded and if the clock of either is affected by jitter there may be some loss in data integrity from the source. Again it is worth considering your application before choosing an appropriate crystal oscillator.