Ic card regulator

An integrated circuit card system comprising;

• a voltage regulator comprising:
• an amplifier having a first input coupled to a reference voltage node and a second input coupled to an output node of the voltage regulator,
• a first transistor having a first conduction terminal coupled to the output node of the voltage regulator, a second conduction terminal coupled to a first supply terminal configured to receive a first supply voltage provided by a contact reader, and a control terminal selectively coupled between the output node of the amplifier and a first voltage node configured to provide a disabling voltage, and
• a second transistor having a first conduction terminal coupled to the output node of the voltage regulator, a second conduction terminal coupled to a second supply terminal configured to receive a second supply voltage provided by an electromagnetic field of a contactless card reader, and a control terminal selectively coupled between the output node of the amplifier and the first voltage node configured to provide a disabling voltage, and
• a supply selection circuit configured to
• couple the first supply terminal to a power supply input of the amplifier via a supply selection circuit output node when a voltage of the first supply terminal is higher than a voltage of the second supply terminal, and
• couple the first supply terminal to a power supply input of the amplifier via the supply selection circuit output node when a voltage of the second supply terminal is higher than a voltage of the first supply terminal.

A method of operating an integrated circuit card comprising a voltage regulator having an amplifier, a first transistor coupled between a first supply terminal and voltage regulator output, and a second transistor coupled between a second supply terminal and the voltage regulator output, the method comprising:

• determining whether the a voltage of the first supply terminal is greater than a voltage of the second supply terminal;
• coupling the first supply terminal to a power supply node of the amplifier and to a control node of the first transistor and disabling the second transistor when the voltage of the first supply terminal is greater than the voltage of the second supply terminal;
• and
• coupling the second supply terminal to the power supply node of the amplifier and to a control node of the second transistor and disabling the first transistor when the voltage of the first supply terminal is not greater than the voltage of the second supply terminal.