A low-power digitally controlled oscillator for all digital phase-locked loops

Abstract

A low-power and low-jitter 12-bit CMOS digitally controlled oscillator (DCO) design is presented. The Low-Power CMOS DCO is designed based on the ring oscillator implemented with Schmitt trigger inverters. The proposed DCO circuit uses control codes of thermometer type to reduce jitters. Performance of the DCO is verified through a novel All Digital Phase-Locked Loop (ADPLL) designed with a unique lock-in process by employing a time-to-digital converter, where both the frequency of the reference clock and the delay between DCO-output and DCO-clock is measured. A carefully designed reset process reduces the phase acquisition process to two cycles. The ADPLL was implemented using the 32nm Predictive Technology Model (PTM) at 0.9V supply voltage, and the simulation results show that the proposed ADPLL achieves 10 and 2 reference cycles of frequency and phase acquisitions, respectively, at 700MHz with less than 67ps peak-to-peak jitter. The DCO consumes 2.2mW at 650MHz with 0.9V power supply. © 2010 J. Zhao and Y.-B. Kim.