This chapter discusses system requirements for a PLL. Noise basics, phase noise, time-domain response, acquisition, jitter, and spurious signals are the system requirements that are studied in detail. In the previous chapter, stability and feedback analysis were discussed, which are also system requirements; however, they are in a chapter by themselves because of their importance and because these requirements are fundamental to understanding how a PLL works.

First, noise basics are discussed in order to lay a foundation for analyzing noise requirements and their relationship to circuit design. Next, phase-noise relationships in oscillators are discussed to give background for analyzing noise and jitter in oscillators. Linear time-domain responses are studied to give an engineer an understanding of the relationship between loop variables, faster switching time, and tracking error. In addition, studying these responses allows damping factor and natural frequency to be determined from measured or simulated step responses. Next, nonlinear acquisition is studied to provide understanding of loop responses to various external stimuli. Understanding these responses will help in understanding loop responses that seem to be inconsistent. Then, the relationships of PLL parameters to jitter are studied to show how to improve timing margin in digital circuits. For synchronizing circuits, reducing jitter will improve the bit-error rate (BER) of the interface. Finally, spurious signals are studied because these signals cause jitter and reduce the precision of the output frequency. Spurious signals at the output from the reference frequency are the largest spurious signals in a loop. Feed-through from the phase...