An ultra compact differentially tuned 6 GHz CMOS LC VCO with dynamic common-mode feedback

A fully integrated 0.024mm2 differentially tuned 6GHz LC VCO for 6+Gbps high speed serial (HSS) links in a 90nm bulk CMOS is presented. It is smaller than any LC-VCO reported to date at this frequency. Its size is comparable with ring oscillators but it has significantly better phase noise. A circuit technique is introduced to dynamically set the common-mode (CM) voltage of the differential varactor control signals equal to the VCO's CM. Using a differential control a very wide tuning range from 4.5GHz to 7.1GHz (45%) is achieved. The VCO has a measured phase noise of -117.7dBc/Hz at a 3MHz offset from a 5.63GHz carrier while dissipating 14mW from a 1.6V supply. © 2006 IEEE.