Reference-free power supply monitor with enhanced robustness against process and temperature variations

Abstract

Power supply noise in current nanometer technologies represents a growing risk, specially because of the uncertainties it produces in the critical paths delays which can result in erroneous computations. Also, these very short variations can affect the functionality of analog circuits like a comparator or an ADC. To tackle with these issues and to have a better power management, on-line power supply monitors have become one common solution. Traditional approaches use an external reference, are very sensitive to temperature and process variations or present high latency. In this work we propose a 3 sigma monitor with a novel detector circuitry that employs a feedback loop that works without an external reference and it is hardened against temperature and process variations. The sensor was designed in the 40 nm CMOS technology node, operating at 1.1 V and has been validated for a temperature range of 0∘C to 85∘C covering all process corners. Also, considering the 3σ confidence, the sensor is able to detect over/undershoots voltage fluctuations up to 2 GHz in the range of -70 mV to +90 mV from the nominal voltage with a maximum latency of 1.1 ns and an energy consumption per measurement of 0.8 pJ.