Benchmark Figure of Merit Extensions for Low Jitter Phase Locked Loops Inspired by New PLL Architectures

Abstract

A conventional figure-of-merit (FOM) for a phase-locked loop (PLL) has served as the most powerful indicator to compare and to normalize performance of different PLL designs. Simply, the conventional FOM is based on the jitter-power trade-off. With a few assumptions, theoretically, it provides a fair comparison. However, as the PLL design techniques have advanced, the assumptions have started breaking. Also, it misses performance impacts from some other important factors other than the jitter and the power. As a result, it is expected that the performance comparison with the conventional FOM is not fair enough for some cases. This work reviews the state-of-the-art PLL design techniques and investigates how those techniques conflict with the assumptions of the conventional FOM. In addition, alternate FOMs which complement the conventional FOM are discussed. To capture complex cross-correlation between various factors, the proposed methodology is to find a correlation between the conventional FOM and other factors from extensive performance surveys, along with quantitative analyses.