An Ultrasonically Powered Optogenetic Microstimulators With Power-Efficient Active Rectifier And Charge Reuse Capability

This paper proposes a novel system for ultrasonically-power optogenetic microstimulator. In this system, a novel powering approach for the comparators is proposed that improves the power conversion efficiency of the rectifier. This is done by lowering the Rail-to-Rail supply voltage of the comparators and consequently their propagation delay. This technique enhances the power conversion efficiency of the active rectifiers in two ways: a. decreasing the propagation delay of the comparators; and b. enabling reuse of consumed power by the comparators and drivers of power transistors. The proposed system including the active rectifier, a novel double-pass regulator, a current reference, and a burst detection circuit is simulated in TSMC 0.18-mu m CMOS technology and occupies an area of 0.09 mm(2). The proposed active rectifier connected to a load of 3 k Omega, generates an output voltage of up to 3 V out of an input AC signal with the amplitude of 3.2V and the frequency range of 1-14 MHz. In the same frequency range and with the same load, it exhibits a voltage conversion ratio of 92.25-93.75% and power conversion efficiency of up to 95%. The double-pass regulator is proposed for seeking both power efficiency and over-voltage protection in this specific design.