A Current Steering Logic Based Ring Oscillator for High Stability and Lower Noise Applications

Ring oscillators are now widely used in digital and mixed-signal circuits for easy integration, however, their phase noise performances are usually worse than those with high Q resonant elements [1]. Comparing with ordinary digital CMOS inverter ring oscillators, the CSL(current steering logic) inverter was proven to provide superior supply noise immunity [2]. However, its characteristics have not been deeply analyzed and it has not been implemented in domestic product line. In this paper, the static and dynamic characteristics of CSL inverter are analyzed and series of CSL inverter ring oscillators with different Gv (The (W/L)s/ (W/L)D shown in Fig. l)and gate areas have been fabricated in 1.2 mum domestic CMOS process. The simulation and experimental results show that CSL ring oscillators have good noise performance and are more immune from supply voltage fluctuation. Therefore, they are suitable for high stability and low noise applications.