An inductively-tuned quadrature oscillator with extended frequency control range

A 5GHz inductively tuned quadrature oscillator designed in a 0.18 mum CMOS technology for high-speed data retiming applications is described. The oscillator is based on a ring architecture with tunable LC delay lines inserted between gain stages to set the operating frequency. The oscillator is tuned by electronically varying magnetic coupling in passive LC delay lines. A 3:1 change in inductance is observed which results in a +/-30% frequency control range. This is shown to be more than sufficient to cover typical process, temperature and supply voltage spreads. The oscillator core operates from a 1.8V power supply and dissipates 46.5 mW.