Heuristic Approach in Ring Voltage Controlled Oscillator Design for V.C.O. Based Analog to Digital Conterters

This paper introduces a procedure that relies on Computer Aided Design tools (industry compatible SPICE simulator and MATLAB) to get a first rapid design solution for a ring voltage controlled oscillator (VCO) that can be further analyzed and optimized for usage in a VCO based analog to digital converter (ADC). Due to the fact that linearity is a key performance metric of an ADC a special attention will be given to this characteristic during the design and for this matter control mechanism will be analyzed. To exemplify the design procedure two different delay cell topologies (simple inverter and pseudo-differential cross-coupled inverters) will be analyzed and designed in a 130 nm CMOS technology.