Ultra Low Power Management Unit for DC Micro Energy Harvester in 018 µm CMOS

Abstract

quotThe thesis discusses the design and simulations of an Ultra Low Power (ULP) newlinePower Management Unit (PMU) for utilization in micro energy harvesters intended for wireless sensor node (WSN) applications, with a focus on achieving newlineenergy autonomy and low power consumption using the subthreshold region newlineof MOSFET. The proposed PMU design comprises a voltage regulator, a voltage newlinemonitor, a battery backup module, and DC-DC Switched Capacitor (SC) converters. To demonstrate the working of the PMU for a real world application, two series connected solar cells provide the input (VIN) to the PMU, which is fed to the newlinevoltage regulator that regulates the output voltage. The PMU is targeted for lowpower applications, and our design objective is to regulate the PMU at nearly 1.0 newlineV. In simulations, we successfully achieved a regulation voltage of 0.95 V, which newlineis sufficient for low power applications. The voltage monitor continuously observes the regulator output voltage and generates a Start/Stop signal, indicating newlinewhether the output voltage is adequate for the load. The PMU consumes 36 nW newlineat 0.98 V, which is the lowest power consumption with the battery backup module newlinereported till date. The PMU observes a maximum efficiency of 72.3% at a higher newlinecurrent value and#8776; 1.0 mA. Different voltages can be tapped from the PMU from 3:2, newline2:1, 3:1, 4:1, and 5:1 SC converters that provide output voltages of 0.67 V, 0.5 V, newline0.33 V, 0.25 V, and 0.2 V to the load, respectively. The standalone converters that newlineconsume slightly more power are operated with a reconfigurable SC converter newlinethat can work as a 3:1 or 2:1 converter, consuming 838 nW. newlineThe second part of the thesis discusses a novel all digital Minimum Energy newlinePoint (MEP) detection architecture consisting of a leakage sensor, a temperature newlinesensor, and an activity sensor. The activity sensor is the iterative delay chain discharge. A candidate circuit is tested at different voltages from a voltage dithering newlineblock connected to the DC DC SC Converters.