Circuit design advances to enable ubiquitous sensing environments

This paper describes critical circuit building blocks for emerging sensing applications, particularly those where volume, and therefore power consumption constraints are orders of magnitude below current state of the art. Developments in ultra-low power microprocessors and memories are described, along with sub-nW timekeeping circuits, pW voltage references, and efficient DC-DC voltage conversion circuits at sub-μA current loads. Taken together, these circuit design advances point to a vision of true mm³ low-cost sensing nodes with hybrid power sources, i.e., scavenged and micro-battery, providing long lifetime and reliable operation.