Impact of Observation Time Window on RTN-Induced Jitter in CMOS Ring Oscillators

At nanometer scale device dimensions, factors that lead to integrated circuit performance variations from one instant in time to another become increasingly significant. Random Telegraph Noise (RTN) is one of the relevant time-dependent variability sources. We perform a simple, physically based analysis that illustrates the impact of RTN on CMOS ring oscillators. Time-domain jitter analysis is used to study the evolution of different jitter metrics over time. We clearly show that the observed jitter may strongly depend on the observation time window. Straightforward expressions for period jitter, cycle-to-cycle jitter and absolute jitter enable evaluation of design choices such as loading, number of stages and bias point on ring oscillator jitter performance. This is relevant not only for circuit design, but also for test and characterization procedures, because metrics such as measurement setup bandwidth and observation time window may impact the outcome of test and characterization procedures. We validate the analytical expressions through simulations and experimental data.