A multi-axis readout circuit using in female ovulation monitoring platform

In this paper, an energy-efficient monitor, including three capacitive and two resistive readout circuits with hardware-sharing architecture, is presented for female ovulation. The proposed design is featuring two calibration modules: one decreases the initial offset by capacitor array, and the other reduces P-V-T variations by taking proportion between sensing and ruler results. After implemented in UMC 0.18μm CMOS-MEMS technology, the post-layout simulation results show that our circuit consumes 30μW and 49μW in 0.8ms conversion time under 1.8V supplied voltage for 1-axis and 3-axis. The capacitive resolution is around 0.1fF and the sensing range of die-temperature is 0~100°C with 0.05°C resolution.