Smart card
AssigneeSTMicroelectronics (Rousset) SAS
InventorOlivier Rouy
Life of this patent
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Abstract
A smart card includes a first circuit delivering a power supply voltage and a second circuit coupled to the first circuit by an electrical conductor and powered with the power supply voltage. A light-emitting diode has a first terminal coupled to the electrical conductor and a second terminal coupled to a first terminal of the second circuit. During a first operating phase, the first circuit delivers a first value of the power supply voltage and the second circuit applies a first voltage to the first terminal. During a second operating phase, the first circuit delivers a second value of the power supply voltage and the second circuit applies a second voltage to the first terminal.
Claims33
A smart card, comprising:
- a first circuit configured to deliver a power supply voltage in response to a supply power received by the smart card, said power supply voltage having a first value during a first operating phase and having a second value during a second operating phase;
- a second circuit coupled to the first circuit by an electrical conductor and configured to be powered with the power supply voltage;
- and
- a light-emitting diode having a first terminal coupled to the electrical conductor and a second terminal coupled to a first terminal of the second circuit;
- wherein the second circuit is configured to apply a first voltage to the first terminal of the second circuit during the first operating phase to ensure that the light-emitting diode is not illuminated regardless of a voltage present on the electrical conductor and further configured to apply a second voltage to the first terminal of the second circuit during the second operating phase that permits a selective illumination of the light-emitting diode depending on the voltage present on the electrical conductor.
A method of controlling a light-emitting diode of a smart card comprising a first circuit and a second circuit coupled by an electrical conductor, the light-emitting diode having a first terminal coupled to the conductor and a second terminal coupled to a first terminal of the second circuit, the method comprising the steps of:
- during a first operating phase:
- delivering, by the first circuit, a power supply voltage at a first value in response to a supply power received by the smart card;
- powering the second circuit with the power supply voltage;
- and
- applying, by the second circuit, a first voltage to the first terminal of the second circuit to ensure that the light-emitting diode is not illuminated regardless of a voltage present on the electrical conductor;
- and
- during a second operating phase:
- delivering, by the first circuit, the power supply voltage at a second value based on the supply power received by the smart card;
- powering of the second circuit with the power supply voltage;
- and
- applying, by the second circuit, a second voltage to the first terminal of the second circuit that permits a selective illumination of the light-emitting diode depending on the voltage present on the electrical conductor.
Dependencies are inferred from the claim text.