A CMOS LC-based frequency reference with ±40ppm stability from −40°C to 105°C

Abstract

This work presents a highly stable monolithic integrated CMOS LC-based frequency reference. The frequency reference is based on a Self-Compensated Oscillator (SCO) architecture where the LC tank operates at a specific phase Phi-NULL where frequency sensitivity versus temperature is minimum. A new compensation technique is applied over Phi-Null to further optimize frequency stability and extend the temperature range. The new technique is based on an analog approach and induces a minimum impact on oscillator phase noise, current consumption and die area. Utilizing this technique, the temperature range has been extended to (-40-105°C) with a ±40ppm frequency stability. Achieved performance makes it possible for the SCO to be introduced to automotive applications where crystals suffer vibration induced stability issues.