Ultra low power management unit

Abstract

This work focuses on design of Minimum Energy Point (MEP) tracking loops.MEP is a point in energy vs. power supply voltage curve for which energy peroperations for a particular circuit is minimum. The design digitally senses the energyand provides supply voltage that a digital circuit should be operated on toachieve MEP.Energy sensing is provided by converting stored capacitive energy to numberof operations that a test circuit can be operated after cutting off the power supply.New methodology for calibrating energy as digital value and comparison ofsensed digital energy is proposed in this work. Droop detection circuit will beused to get number of operations during power supply is cut-off and will be capturedby counter then table based comparison method will be implemented withpower efficient shift and add unit.Finally calculator finds maximum number of operations that are related to minimumenergy consumption. Calculator will be made custom so that it can beredesigned for different supply voltages.Circuit successfully tracks MEP in sub threshold region for different adder circuits.MEP for 1 bit FA is found at 0.4V, threshold voltage for NMOS is 0.47Vand for PMOS it is 0.54V. Similarly MEP of 4 and 8 bit adders are at 0.5V. Overallenergy consumption for MEP tracking is 229.04 nJ. Overall power for unit is 1.636mW. Overhead energy and power of unit are 227.92 nJ and 1.628mWrespectively.