Design of a fully integrated CMOS highly temperature stable frequency reference

Abstract

A new fully integrated frequency reference has been designed, fabricated and measured. The goal of the design procedure has been high stability of the frequency over temperature variations. This should be achieved using a CMOS technology without MEMS and crystals, while being restricted by a very low power budget. The frequency is designed based on an RC time constant, where both R and C are integrated on chip. The novel topology is minimizing the sources of error that affect the frequency being produced (minimum offsets and delays that spread over temperature). According to the simulations, the fabricated oscillator is a competitive one among the RC-time-constant based ones, but the measurements showed that the tradeoff between performance and integration (accompanied with power minimization) is worse than its counterparts (MEMs based or LC based all-silicon choices), or its quartz crystal based ancestor. Ways to increase the quality even further are proposed.