VCO-based ADCs for IoT applications

Internet of things (IoT) benefits from fast and low cost development of technology portable re-configurable hardware. Low power consumption is desired for applications operating from harvested or limited energy. Subthreshold operation of VCO-based ADCs is investigated in this work in order to meet these challenges. A ring VCO built using NAND gates is used for reliable operation in the subthreshold region. The impact of supply scaling and PVT variations on the VCO characteristics as well as on the converter performance is studied using transistor level simulations. Some solutions are suggested towards energy efficient operation over a wide range of PVT conditions.