Circuit design in mm-scale sensor platform for future IoT applications

Since the emergence of the first computers in the 1940s, many different classes of computing systems, such as workstations, desktop PCs, and laptops, have been introduced to meet the ever-changing market needs, as predicted by “Bell’s Law." Light-weight mobile computing devices were introduced in the early 2000s, and we expect to be surrounded by millions or trillions of small sensing/computing systems in the upcoming internet of things (IoT) era. Sensor systems in the IoT era are expected to be several orders of magnitude smaller in volume than their predecessors, consistent with the general trend of increasing compactness observed as computing systems evolve. This means that computing systems with a volume on the order of cubic centimeters or even cubic millimeters are likely. Recent research shows that mm-scale systems can be realized with advances in low-power electronics design, packaging, and battery technologies. These miniature systems are expected to be the driving force for unprecedented IoT applications, such as implanted diagnosis sensors and pervasive environment monitoring sensors. The key challenge for achieving mm-scale volume is to significantly reduce the power used by every component of a system due to the extremely limited amount of energy storage. Therefore, in this chapter, state-of-the-art low-power design strategies for a few core components which enable such mm-scale systems are reviewed. System-level design approach is also presented with a few recently demonstrated mm-scale sensing systems.