Analysis and design of a linear voltage controlled ring oscillator with rail-to-rail tuning range and zero static power

Abstract

ABSTRACTThis paper analyses and designs a linear voltage controlled ring oscillator (VCRO) with rail-to-rail tuning range and zero static power. The rail-to-rail tuning range is achieved via adding a PMOS tuning transistor and corresponding current mirror into the conventional current-starved inverter with only a NMOS tuning transistor. The static power is eliminated via introducing a control-pulse-generating auxiliary circuit to guarantee only a dynamic power during the transition times. The linearity, i.e. global tuning gain over the rail-to-rail tuning range is obtained via doing a theoretical tuning gain analysis in the piecewise ranges to determine the ratios of the transistors. Besides, the phase noise is predicted by transplanting an analytical method of the flicker noise. Finally, the proposed VCRO is verified by Cadence Spectre-Virtuoso in the CSMC CMOS 180 nm process.