Adjustable Voltage Sensors for Power Supply Chains in Passive UHF RFID Transponders

In passive UHF RFID transponders, a storage capacitor is used to supply the tag´s subsystems. A quick charge of the storage capacitor and a sufficient supply voltage for the subsystems are intended for proper operation, thus using a voltage sensor. This paper presents two adjustable very low power consumption voltage sensor circuits for the supply capacitor in passive UHF RFID transponders. The proposed circuits sense the charge stored in a supply capacitor and enable 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 two solutions is below 100 nA, for a supply voltage between 2.5 V and 3.3 V