Energy harvesting and limits of low power mixed-signal circuit design

Wireless sensors and implantable medical devices have driven IC design to extremes of low power consumption to maximize system operating lifetimes from fixed energy stores or from energy harvested from the environment. Reaching the limits of miniaturization will require approaching the limits of power dissipation. We describe three key sensor subsystems: integrated diodes for solar energy harvesting, efficient microwatt power conversion circuits, and supply-voltage-ripple-tolerant digital circuits. We then extrapolate from these examples to find the minimum surface area and volume required for energy harvesting sensors.