A 0.9-2.6pW 0.1-0.25V 22nm 2-bit Supply-to-Digital Converter Using Always-Activated Supply-Controlled Oscillator and Supply-Dependent-Activation Buffers for Bio-Fuel-Cell-Powered-and-Sensed Time-Stamped Bio-Recording. - Hiroaki Kitaike; Masaharu Inada; Mitsuru Terauchi; Hironori Tagawa; Ryosuke Nagai; Shufan Xu; Ruilin Zhang; Kunyang Liu; Kiichi Niitsu (VLSI Technology and Circuits, 2024)