This work presents a high-efficiency ultrasound energy harvesting interface with auto-calibrated timing control, featuring: 1) the proposed CP auto-calibration, consisting of the half bias-flip time (thalf ) detection and adaptive closed-loop time calibration (ACTC) to improve the system's robustness against piezoelectric transducer (PZT) materials and environmental variations; 2) the proposed charge recycling (CR) bootstrapping driver to reduce conduction loss and improve the C auto-calibration accuracy as well as the peak voltage flipping efficiency (η) and 3) the proposed coarse detection and fine calibration technique to eliminate the inherent timing offset and increase the acceptable input excitation frequency range. The fabricated chip prototype in 0.18-μ m silicon on insulator (SOI) CMOS process can adapt to both PZT5A (nominal C ∼ 114 pF) and PZT5H (nominal C ∼ 190 pF) and is capable of operating over a wide temperature range from - 25 °C to 85 °C. The proposed CP auto-calibration and CR bootstrapping driver can improve the η to as high as 93.6% at an output power of 496.6 μ W. With the proposed coarse detection and fine calibration technique, this work demonstrates a high measured peak power conversion efficiency (PCE) of 94.5%, corresponding to a ∼ 23% improvement when compared with the prior ultrasound energy harvesting interface while achieving a favorable figure of merit (FoM) of 8.13×.