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.

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.

An open loop control unit is provided to monitor an output power of a charge pump converter having an input impedance and a first input impedance controlling terminal configured to be plugged to the open loop control unit and modify the input impedance. The open loop control unit includes at least a reference circuit to sense the output power of the charge pump converter and at least one control circuit to receive the difference value, establish a trim value, and send the trim value to the impedance controlling terminal so as to modify the input impedance.

A power control unit is provided to monitor the output power of a charge pump converter having an input impedance and an input impedance controlling terminal to be plugged to the power control unit and modify the input impedance. The power control unit includes a control circuit sense the output power of the charge pump converter and a control unit to receive the sensed power value, establish a control value, and send the control value to the impedance controlling terminal so as to modify the input impedance.

A Radio Frequency Identification (RFID) tag is disclosed. The RFID tag includes an antenna port to receive an input AC signal and a hybrid limiter including a clamping device configured to limit a voltage of the input AC signal to a preconfigured limit. The hybrid limiter is configured to provide a stable ground reference for the clamping device.

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.

A ground switch is disclosed. The ground switch includes an antenna port, a pair of switching devices coupled with the antenna port and a charge pump coupled with the pair of devices and configured to turn on/off the pair of devices based on an AC input signal received through the antenna port and a DC offset voltage added to the AC input signal. The ground switch further includes a clamping circuit to clamp an output of the charge pump. The ground switch is configured to provide a stable ground to components of devices such that a radio frequency identification (RFID) device.

A charge pump for a Radio Frequency Identification (RFID) tag is disclosed. The charge pump includes an antenna port to receive an input AC signal, an input port to receive an input signal, and a main transistor having a gate, a source and a drain. A threshold voltage cancellation circuit is included and is coupled between one terminal of the antenna port and the input port, wherein an output of the threshold voltage cancellation circuit is configured to drive the gate of the main transistor. The threshold voltage cancellation circuit is configured to reduce the threshold voltage of the main transistor when the voltage of the input signal is below a predefined voltage level and to remove threshold voltage cancellation when the voltage of the input signal is above the predefined voltage levels.

A rectifier cell for rectifying an electrical AC voltage, which rectifier cell comprises a transistor series circuit having a first field effect transistor and a second field effect transistor. A first frequency-independent voltage divider connected in parallel with the transistor series circuit has a first node which is connected to the gate electrode of the first field effect transistor. A second frequency-independent voltage divider connected in parallel with the transistor series circuit has a second node which is connected to the gate electrode of the second field effect transistor. In this case, the first and the second node of the frequency-independent voltage dividers are additionally each connected to earth via a bias capacitor.

In accordance with a first aspect of the present disclosure, a radio frequency identification (RFID) transponder is provided, comprising: at least one functional component configured to perform a function of the RFID transponder; a charge pump configured to supply an output voltage to said functional component, wherein said charge pump comprises a plurality of charge pump stages; a charge pump controller configured to control a number of charge pump stages which contribute to the output voltage. In accordance with a second aspect of the present disclosure, a corresponding method of operating an RFID transponder is conceived.