A 44–93- 250–400-mV 0.18- CMOS Starter for DC-Sourced Switched-

Although microsystems can replenish batteries and energize modules with ambient energy without having to store much energy on board, on-chip photovoltaic cells and thermoelectric generators generate 50-400 mV, which is usually not sufficiently high to operate transistors. Although stacking cells is possible, the tradeoff in power is ultimately unfavorable because small transducers output little power. Thankfully, transformers can boost millivolt voltages but not without a significant toll on space. Motion-propelled microelectromechanical system switches can also start a harvester but only in the presence of vibrations. Moreover, although 50-300-mV ring and LC oscillating networks can charge batteries, initialization requires 1-15 ms. The prototyped 0.18-μm CMOS oscillating starter presented here draws power from 250-450 mV to charge 100 pF to 0.32-1.55 V in 44-92 μs. In the steady state, the cost of the starter to the direct-current-sourced harvester it supports is only a 1.8% drop in the power conversion efficiency.