Algorithm for achieving minimum energy consumption in CMOS circuits using multiple supply and threshold voltages at the module level

This paper proposes an optimum methodology for assigning supply and threshold voltages to modules in a CMOS circuit such that the overall energy consumption is minimized for a given delay constraint. The modules of the circuit should have large enough gate depths such that the delay and energy penalties of the level shifters connecting them are negligible. Both static and dynamic energy are considered in the optimization. Energy savings of up to 48 % have been achieved on various example circuits. The first step in the optimization finds optimum supply and threshold voltages for each module in the circuit. If the circuit has a large number of modules, this step might yield a correspondingly large number of different supply and threshold voltages for minimum energy consumption. Since having a large number of different supply and threshold voltages on an IC is not feasible in current technologies, an additional step clusters the multiple voltages obtained from the first step into a fixed number of supply and threshold voltages (for example, 2 different supply voltages and 2 different threshold voltages). In addition to the application of this method to circuit optimization, it can also be applied to a wide range of problems with delay constraints, such as software tasks running on a dynamically variable VDD and Vth processor