Voltage sensors for supply capacitor in passive UHF RFID transponders

This paper presents two very low-power consumption voltage-sensor circuits for the supply capacitor in passive UHF RFID transponders. The proposed circuits are key points in a battery-life-free RFID tag, by sensing the charge stored in a supply capacitor, and enabling the rest of the system when enough charge is available. In comparison to previous published circuits, the average current of our circuits is one order of magnitude lower. The average current consumption for our solutions is below 100 nA, for a supply voltage between 2.5 V and 3.3 V. In addition, we have proposed some modifications to the best published results; and diminished the power consumption one order of magnitude.