Ultra-Low Power VLSI Circuit Design Demystified and Explained: A Tutorial

In this paper, the state of the art in ultra-low power (ULP) VLSI design is presented within a unitary framework for the first time. A few general principles are first introduced to gain an insight into the design issues and the approaches that are specific to ULP systems, as well as to better understand the challenges that have to be faced in the foreseeable future. Intuitive understanding is accompanied by rigorous analysis for each key concept. The analysis ranges from the circuit to the micro-architectural level, and reference is given to process, physical and system levels when necessary. Among the main goals of this paper, it is shown that many paradigms and approaches borrowed from traditional above-threshold low-power VLSI design are actually incorrect. Accordingly, common misconceptions in the ULP domain are debunked and replaced with technically sound explanations.