10 GHz VCO for 0.13/spl mu/m CMOS Sonet CDR

A 10 GHz VCO with 1.3:1 K_VCO variation and 2 MHz/V supply pushing is developed for a dual channel Sonet CDR IC using MOS inversion mode varactors with their backgates tied to a common mode voltage and with an automatic leveling loop to control oscillator amplitude and varactor linearization. Three such oscillators are combined with buffers and a passive switch MUX to achieve an 8-12 GHz tuning range and 27mW DC power consumption on a 1.8V unregulated supply. The VCOs are fabricated in a 0.13mum CMOS digital process with added MIMCAP support but thin metal interconnect using thick oxide transistors normally provided for 3V I/O. A moderate -112 dBc/Hz phase noise at 1 MHz offset is achieved which is sufficient to exceed OC-192 Sonet random jitter generation requirements by a factor of 2