Jitter optimization based on phase-locked loop design parameters

Abstract

This paper investigates the effects of varying phaselocked loop (PLL) design parameters on timing jitter. The noise due to voltage-controlled oscillator (WO), input clock and buffering clock are considered. First, a closed-form equations are derived that relate PLL output clock jitter to parameters of a second-order PLL, i.e., damping factor and bandwidth. Then the second-order analysis is extended to a third-order PLL with inherent feedback/sampling delay. The sensitivity study clearly illustrates how to select design parameters to obtain minimum output jitter. To verify the analysis experimentally, a digitally tunable PLL architecture is designed and fabricated that allows independent adjustment of loop parameters. The design not only demonstrates the agreement between analysis and theory, but also shows an architecture that minimizes jitter.