Power recovery circuit for battery-less TPMS

A 13.56 MHz HF power recovery circuit was designed for batteryless tire pressure monitoring system (TPMS) or wireless sensor networking applications using chartered 0.35-mum CMOS technologies. It converts received HF power to DC and charges a large capacitor, then supplies stable voltage output for other modules. Simulation results show that the circuit operates normally at electromagnetic field strength with induced voltage above 0.3 v. The circuit also generates an enable signal for digital circuits when the capacitor has been charged to a certain extent.