A Radio Frequency Identification (RFID) tag is disclosed. The RFID tag includes an antenna to receive a high frequency signal, a capacitor bank coupled with the antenna, a charge pump coupled with the antenna configured to convert the high frequency signal to a direct current (DC) signal, an envelope detector to measure peak voltage of the high frequency signal and a detector to compare an output of the charge pump and an output of the envelope detector. The RFID tag also includes an impedance tuning circuit coupled with the charge pump and the envelope detector configured change a capacitance of the capacitor bank based on an output of the detector and the envelope detector.

A Radio Frequency Identification (RFID) tag is disclosed. The RFID tag includes an antenna to receive an input AC signal and a tuning system coupled with the antenna to optimize signal strength of the input AC signal. The tuning system includes a charge pump rectifier. A diode rectifier is included and is coupled with the antenna to receive the input AC signal after the tuning system optimizes the signal strength by tuning input impedance of the antenna.

There is described a rectifier circuit for providing and limiting a supply voltage to an RFID tag, the circuit including a pair of antenna input terminals configured to receive an input signal from an RFID tag antenna. A plurality of charge pump stages are coupled in cascade in such a way that an input terminal of a first charge pump stage in the cascade is connected to ground and an input terminal of each subsequent charge pump stage in the cascade is coupled to an output terminal of the preceding charge pump stage in the cascade. A control logic is configured to select the output terminal of one charge pump stage among the plurality of charge pump stages to provide the supply voltage. Furthermore, an RFID tag and a method of providing and limiting a supply voltage to an RFID tag are described.

A dual frequency HF-UHF RFID integrated circuit including a power supply. The power supply includes: an HF branch including an HF rectifier and a linear voltage regulator, wherein the HF rectifier is configured to be connected to a resonance circuit formed by a HF antenna-coil and a resonance capacitor and wherein the HF rectifier is connected to the linear voltage regulator; a UHF branch including a UHF rectifier and a shunt voltage regulator, wherein the UHF rectifier has a charge pump and is configured to be connected to a UHF antenna and wherein the UHF rectifier is connected to the shunt voltage regulator; and a supply line, wherein the linear voltage regulator and the shunt voltage regulator are both connected to the supply line of the power supply.

A voltage limiter incorporated in a radio frequency identification (RFID) integrated circuit (IC) for a RFID tag is disclosed. The RFID IC includes a radio frequency (RF) rectifier and a clock generator. The RF rectifier is configured to convert an AC signal received from an antenna incorporated in the RFID tag to a DC signal. The voltage limiter includes a current sink device coupled between output of the RF rectifier and ground and a charge pump to control conduction of current through the current sink device to limit output voltage of the RF rectifier to a predefined voltage level.

The integrated circuit includes a first node intended to be biased at a first voltage, a second node intended to be biased at a second voltage and having a non-negligible capacitive coupling with the first node. A power supply management device comprises a voltage booster configured to boost a power supply voltage and comprising boost stages configured to generate intermediate voltages on intermediate nodes. A compatibility detection circuit is configured to detect compatibility between the second voltage and one of the intermediate voltages, and, if the second voltage is compatible with an intermediate voltage, to couple the at least one second node to the compatible intermediate node.

An internal voltage generator of a smart card and a smart card including the same. The internal voltage generator may include: a mode detector that generates a mode signal indicating a contact mode or a contactless mode; a low-drop out (LDO) regulator including an error amplifier, where the LDO regulator is responsive to the mode signal to: in the contact mode, drive the error amplifier with a second driving voltage to generate an error voltage, and regulate the second driving voltage based on the error voltage to generate a first output voltage, and in the contactless mode, drive the error amplifier with the first driving voltage to generate the error voltage, and regulate the second driving voltage based on the error voltage to generate the first output voltage.

The present disclosure provides a circuit and a method for improving energy harvest for an RFID tag with a temperature sensor, where an instruction command sent by a card reader includes a modulated part to invoke temperature sensor functions, and an unmodulated constant-envelop RF signal part with an extended time of duration to charge a switched additional energy storage capacitor embedded in the circuit. The switched additional energy storage capacitor is connected to the circuit upon a mode control signal corresponding to the sensor operation mode of the RFID tag. Thus, the RFID tag with the temperature sensor is ensured to conform to the timing window protocol for regular downlink operations, and at the same time, is capable of meeting higher energy demand for a high accuracy temperature sensor operation.

In accordance with a first aspect of the present disclosure, a radio frequency identification (RFID) transponder is provided, comprising a charge pump and at least one functional component, wherein: the charge pump is configured to convert an input voltage into an output voltage and to supply the output voltage to the functional component; the functional component is configured to perform a function of the RFID transponder using the output voltage of the charge pump; wherein the charge pump comprises a diode or switch transistor and at least one capacitor coupled to said diode or switch transistor, and wherein the capacitor is configured to compensate for a change of an impedance of said diode or switch transistor. In accordance with a second aspect of the present disclosure, a corresponding method of operating an RFID transponder is conceived.

A hybrid document includes a flexible document having visible markings. One or more light-controlling elements and a controller are embedded in or on the flexible document. The controller is electrically connected to the one or more light-controlling elements to control the one or more light-controlling elements. A power input connection is electrically connected to the controller, or one or more light-controlling elements, or both. A power source can be connected to the power input connection, for example a piezoelectric or photovoltaic power source. In response to applied power, the controller causes the one or more light-controlling elements to emit light. In some embodiments, the controller includes a memory and a value can be stored in the memory and displayed by the light-controlling element(s). In some embodiments, the value can be assigned or varied by a hybrid currency teller machine.