Design of a crystal oscillator for an all-digital phase-locked loop in 0.18um CMOS

A phase-locked loop (PLL) is widely used on many integrated circuits to provide an accurate and stable clock. A PLL uses negative feedback around an on-chip oscillator that the feedback loop constantly adjusts to match the phase and frequency of an input reference clock. This project focused on the design of a crystal oscillator in 0.18 um CMOS, which is used to provide an accurate reference clock for an all digital phase-locked loop. This design makes use of an on-chip oscillator which utilizes an external off-chip crystal to provide a highly accurate frequency. The crystal oscillator circuit was designed using Cadence Virtuoso computer-aided design (CAD) software, and verified using the Spectre circuit simulator across different process, supply voltage, and temperature (PVT) variations.