Smart card

Abstract

Embodiments of the present disclosure relate to a smart card. The smart card includes a first circuit that delivers a supply voltage, and a second circuit that is coupled to the first circuit via an electrical conductor and powered by the supply voltage. A light-emitting diode has a first terminal coupled to the electrical conductor and a second terminal coupled to the first terminal of the second circuit. During a first operating phase, the first circuit delivers a first value of the supply voltage, and the second circuit applies the first voltage to the first terminal. During a second operating phase, the first circuit delivers a second value of the supply voltage, and the second circuit applies a second voltage to the first terminal.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority of French patent application No. 2011736, filed on November 16, 2020, the contents of which are incorporated herein by reference in their entirety to the maximum extent permitted by law. Technical Field

[0003] The present disclosure relates generally to electronic devices and, more particularly, to smart cards. Background Art

[0004] Many applications use smart cards (e.g. payment cards, transport cards, personal identification cards, etc.). Among current microcircuit cards, cards equipped with biometric sensors are particularly well known. Biometric sensors can usually perform, for example, an identity verification for each use of the card.

[0005] There is a need to improve current smart cards, particularly current smart cards that include biometric sensors. For example, it is desirable for a smart card to be able to display information to a user. Summary of the Invention

[0006] One embodiment overcomes all or some of the shortcomings of current smart cards, particularly current smart cards that include biometric sensors.

[0007] One embodiment provides a smart card comprising: a first circuit configured to deliver a supply voltage from supply power received by the card; a second circuit coupled to the first circuit via an electrical conductor and configured to be powered by the supply voltage; and a light emitting diode having a first terminal coupled to the electrical conductor and a second terminal coupled to the first terminal of the second circuit; wherein, during a first operating phase, the first circuit is configured to deliver a first value of the supply voltage and the second circuit is configured to apply a first voltage to the first terminal of the second circuit, and during a second operating phase, the first circuit is configured to deliver a second value of the supply voltage and the second circuit is configured to apply a second voltage to the first terminal of the second circuit.

[0008] One embodiment provides a method for controlling a light-emitting diode of a smart card, the 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 the first terminal of the second circuit, the method comprising the following steps: during a first operating phase: the first circuit delivers a supply voltage at a first value from a supply power received by the smart card; the second circuit is powered by the supply voltage; and the first voltage is applied to the first terminal of the second circuit by the second circuit; and during a second operating phase: the first circuit delivers a supply voltage at a second value based on the supply power received by the smart card; the second circuit is powered by the supply voltage; and the second circuit applies a second voltage to the first terminal of the second circuit.

[0009] According to one embodiment, the first circuit and the second circuit are configured to communicate via said electrical conductor during the first phase.

[0010] According to one embodiment, during the first phase, the first circuit and the second circuit are configured to enable switching of the voltage of the electrical conductor between a zero value and a first value of the supply voltage.

[0011] According to one embodiment, during the first phase, the first circuit or the second circuit, preferably the first circuit, is configured to implement one or more switchings of the voltage of the electrical conductor between a zero value and a second value of the supply voltage.

[0012] According to one embodiment, the second value of the supply voltage is greater than the first value of the supply voltage.

[0013] According to one embodiment, the second value of the supply voltage is greater than a conduction threshold of the diode, and the first value of the supply voltage is less than the conduction threshold of the diode.

[0014] According to one embodiment, the second value of the supply voltage is smaller than a maximum supply voltage of the second circuit.

[0015] According to one embodiment, the smart card further comprises a biometric sensor, preferably a fingerprint sensor, which is configured to be powered by the supply voltage delivered by the first circuit.

[0016] According to one embodiment, the second circuit and the biometric sensor are configured to communicate with each other.

[0017] According to one embodiment, the sensor is configured to operate with a supply voltage comprised within a range of values smaller than a second value and including the first value, the sensor being further configured to withstand the supply voltage at the second value.

[0018] According to one embodiment, the first circuit is further configured to set the electrical conductor to a high impedance state by switching from a first voltage to a second voltage at the first terminal of the second circuit by the second circuit.

[0019] According to one embodiment, the first terminal is an anode of the diode, the second terminal is a cathode of the diode, the first voltage is equal to the supply voltage at a first value, and the second voltage is zero.

[0020] According to one embodiment, the first terminal is a cathode of the diode, the second terminal is an anode of the diode, the first voltage is zero, and the second voltage is equal to the supply voltage at a second value.

[0021] According to one embodiment, the card further comprises an additional electrical conductor coupling the first circuit to the second circuit and an additional light emitting diode having a first terminal coupled to the additional electrical conductor and a second terminal coupled to the first terminal of the second circuit.

[0022] According to one embodiment, the supply voltage is received via an electromagnetic field emitted by the card reader or via direct electrical contact of the smart card with the card reader. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above features and advantages and other features and advantages will be described in detail in the following description of specific embodiments given by way of illustration and not limitation, with reference to the accompanying drawings, in which:

[0024] Figure 1 One embodiment of a smart card in communication with a card reader is shown very schematically in block form;

[0025] Figure 2 yes Figure 1 A timing diagram of an implementation of the method in a smart card of the type;

[0026] Figure 3 Shown by Figure 1 Smart card implementation Figure 2 A timing diagram of an example of a method;

[0027] Figure 4 The diagram is shown very schematically in the form of a box. Figure 1 An alternative embodiment of the smart card;

[0028] Figure 5 The diagram is shown very schematically in the form of a box. Figure 1 Another alternative embodiment of the smart card. DETAILED DESCRIPTION

[0029] In different drawings, the same features are designated by the same reference numerals. In particular, common structural and / or functional features in various embodiments may have the same reference numerals and may be provided with the same structure, dimensions, and material properties.

[0030] For the sake of clarity, only those steps and elements that are useful for understanding the embodiments described herein are illustrated and described in detail. Specifically, data exchange between a smart card and a card reader, via an electromagnetic field emitted by a card reader and received by a card, or through direct electrical contact between the card reader and the card, and power supply provided by the card reader to the smart card are not described in detail. The described embodiments, implementation modes, and variations are compatible with conventional data exchange between a card and a card reader, and conventional power supply provided by a card reader to a card.

[0031] Unless otherwise stated, when referring to two elements being connected together, this means a direct connection without any intermediate elements other than conductors, and when referring to two elements being coupled together, this means the two elements may be connected or they may be coupled via one or more other elements.

[0032] In the following disclosure, unless otherwise stated, when referring to absolute position qualifiers (such as terms "front", "back", "top", "bottom", "left", "right", etc.) or relative position qualifiers (such as terms "above", "below", "upper", "lower", etc.) or directional qualifiers (such as "horizontal", "vertical", etc.), reference is made to the orientation shown in the figures.

[0033] Unless otherwise indicated, the expressions "about," "approximately," "substantially," and "on the order of" mean within 10%, preferably within 5%.

[0034] Figure 1 An embodiment of a smart card 1 in communication with a card reader (not shown) is shown very schematically in block form. Card 1 is, for example, a payment card, a transportation card, a personal identification card, etc. The card reader is, for example, a payment terminal, a transportation ticket verification terminal, an access control terminal, etc.

[0035] The card reader is configured to emit an electromagnetic field EMF, for example a radio frequency field having a wavelength, for example, in the range of 3 kHz to 3 GHz.

[0036] When the card 1 is within range of the reader, it receives or captures the field EMF.

[0037] The smart card 1 comprises a circuit 100. The circuit 100 is configured to generate a supply voltage Vdd as a function of a field EMF received by the card 1. More specifically, the circuit 100 is configured to deliver a plurality of values of the voltage Vdd.

[0038] For example, the card 1 includes an antenna 102 (block “Antenna”) that captures the field EMF and delivers a voltage and current corresponding to the circuit 100. For example, the circuit 100 includes a circuit 104 (block “Power”) that is configured to generate a DC voltage (DC) from the power provided to the circuit 100 by the antenna 102, from which the voltage Vdd is obtained, for example.

[0039] As an example, the circuit 100 includes a microcontroller 106 (block "μC1"). The microcontroller 106 is, for example, configured to control one or more communication modules (not shown) of the circuit 100. This module or modules, for example, enables inverse modulation of the received field EMF to transmit data to a card reader, and, for example, demodulation of the received field EMF to receive data from the card reader. The microcontroller 106 is, for example, configured to control the circuit 104.

[0040] exist Figure 1 In the example of FIG. 1 , the card 1 receives electrical energy, ie, supplies power, due to the field EMF emitted by the card reader.

[0041] In another example, not shown, card 1 receives the supplied electrical power delivered by the card reader due to the electrical contacts between the card reader and card 1. In this other example, card 1 may not include antenna 102. In this other example, circuit 100 is configured to generate a voltage Vdd that can take multiple values based on (i.e., in accordance with) the electrical power provided by the card reader and received by card 1. For example, circuit 104 is configured to receive a DC voltage available at the electrical contacts of card 1, wherein voltage Vdd is obtained, for example, from this DC voltage. In this other example, card 1 includes, for example, a communication module controlled by its microcontroller 106 and configured to exchange data with the card reader via signals transmitted between the card 1 and the card reader via the electrical contacts between the card 1 and the card reader.

[0042] In yet another example, not shown and corresponding to a combination of the above two examples, the card 1 is configured to receive power supply via the electromagnetic field emitted by the card reader and also to receive power supply via electrical contact with the card reader. The card 1 is also configured to exchange data with the card reader via the electromagnetic field emitted by the card reader and also to exchange data with the card reader via electrical signals transmitted between the card 1 and the card reader due to electrical contact between the card 1 and the card reader.

[0043] According to one embodiment, the circuit 100 (eg the microcontroller 106 thereof) comprises a secure element (not shown) having identification data of the holder of the card 1 stored therein.

[0044] The card 1 further comprises a circuit 108 (block "μC2"), for example a microcontroller 108. The microcontroller 108 is powered by a voltage Vdd.

[0045] At least one electrical conductor (typically a wire) couples the circuit 100 (e.g., its microcontroller 106) to the microcontroller 108. Figure 1 In FIG, a single electrical conductor 110 has been shown. One end of the conductor 110 is connected to the circuit 100, for example to the microcontroller 106, preferably to an input / output of the circuit 100 or its microcontroller 106 of the GPIO (“General Purpose Input Output”) type.

[0046] Circuits 100 and 108 are configured to communicate with each other via electrical conductors coupling them, in particular, via conductor 110 .

[0047] For example, on each conductor, and in particular, on conductor 110 via which circuits 100 and 108 communicate, circuit 100 or its microprocessor 106, on the one hand, and / or microcontroller 108, on the other hand, is configured to switch the voltage on the conductor between a low value of zero and a high value, the high value being equal to the current value of voltage Vdd. For example, during the transmission of a bit between circuits 100 and 108 via conductor 110, when voltage VC on the conductor is zero, this encodes a first binary state of the transmitted bit, and when voltage VC is equal to Vdd, this encodes a second binary state of the transmitted bit.

[0048] According to one embodiment, the card 1 includes a biometric sensor 112 (box “Sensor”). Preferably, the sensor 112 is a fingerprint sensor. The sensor 112 is powered by a voltage Vdd. In addition, the sensor 112 and the microcontroller 108 are configured to communicate with each other, for example via one or more wires 114 coupling the circuits 108 and 112. Figure 1 A single conductor 14 is shown in FIG. For example, the voltage on each conductor 114 can be switched between a low value of zero and a high value equal to the current value of voltage Vdd to encode a first binary state and a second binary state, respectively, of a bit transmitted via that conductor 114.

[0049] The card 1 also includes a light emitting diode or LED 116. The LED 116 has: a first terminal, e.g. Figure 1 , wherein the first terminal is coupled (eg, connected) to the lead 110; and the second terminal, eg, Figure 1 At its anode, the second terminal is coupled (eg, connected) to terminal 118 of circuit 108 .

[0050] In a first operating phase, the circuit 100 is configured to deliver the voltage Vdd at a first value V1 .

[0051] Preferably, the value V1 is such that the microcontroller 108 is correctly powered, i.e., the microcontroller 108 is able to perform its various functions when the microcontroller 108 is powered with the voltage Vdd at the value V1. In other words, the microcontroller 108 is configured to be powered with a voltage between the high value VH1 and the low value VL1, and the value V1 is between these values VL1 and VH1.

[0052] Similarly, the sensor 112 is preferably properly powered with the voltage Vdd at the value V1, i.e., the sensor 112 is able to perform its various functions when powered with the voltage Vdd at the value V1. In other words, the sensor 112 is configured to be powered with a voltage between the high value VH2 and the low value VL2, and the value V1 is between these values VL2 and VH2.

[0053] If a voltage at value V1 is applied across LED 116, the voltage at value V1 is insufficient to illuminate LED 116. In other words, value V1 is less than a turn-on threshold Vth of LED 116.

[0054] Furthermore, during this first operating phase, the circuit 108 is configured to apply a first voltage to its terminal 118. The first voltage applied to the terminal 118 during the first phase may be at most equal to the supply voltage Vdd of the circuit 108, i.e. V1 during the first phase, the first voltage being determined such that the LED 116 does not conduct, regardless of the value of the voltage VC on the conductor 110. More specifically, during Figure 1 In the example shown in FIG1 , where the anode of LED 116 is coupled to terminal 118, the first voltage is zero voltage. Therefore, regardless of the value of voltage VC during the first phase, that is, voltage VC is zero or equal to V1, voltage VL across LED 116 (referenced to the cathode of LED 116) is zero or negative. Voltage VL is therefore less than the conduction threshold Vth of LED 116, and LED 116 does not conduct.

[0055] According to one embodiment, the first operating phase of card 1 corresponds to a communication phase between circuits 106 and 108, during which data are exchanged between these circuits 106 and 108, in particular via conductor 110. Preferably, communication between microcontroller 108 and sensor 112 also takes place during this first phase.

[0056] In a second operating phase, the circuit 100 is configured to deliver the voltage Vdd at a second value V2. The value V2 is greater than the value V1.

[0057] Preferably, the value V2 is such that the microcontroller 108 is correctly powered, ie the microcontroller 108 is able to perform its various functions when the microcontroller 108 is powered with the voltage Vdd at the value V2. In other words, the value V2 is between the values VL1 and VH1.

[0058] However, preferably, the voltage Vdd at the value V2 cannot properly power the sensor 112. In other words, the value V2 is, for example, greater than the value VH2. Therefore, when the voltage Vdd is at the value V2, the sensor 112, for example, cannot perform its function.

[0059] Furthermore, the value V2 is determined so that when the voltage Vdd is at the value V2, the sensor 112 is not degraded or damaged by the value V2 of the supply voltage Vdd. In other words, the sensor 112 is configured to withstand the supply voltage Vdd at the value V2.

[0060] The value V2 is further greater than the turn-on voltage Vth of the LED 116. In other words, if a voltage at the value V2 is applied across the LED 116, the voltage is sufficient to cause the LED 116 to emit light.

[0061] Furthermore, during this second operating phase, the circuit 108 is configured to apply a second voltage to its terminal 118. More specifically, during Figure 1 In the example of FIG1 , in which the anode of LED 116 is coupled to terminal 118, the second voltage is the supply voltage Vdd, which is then equal to V2 during the second operating phase. Thus, depending on the value of voltage VC during the second phase, i.e., whether voltage VC is zero or equal to V2, the voltage VL across LED 116 is equal to V2 or zero, respectively. Since value V2 is greater than the conduction threshold Vth of LED 116, this causes circuit 100 and / or circuit 108 to control the lighting phase or non-lighting phase of LED 116 by switching voltage VC on conductor 110 between zero and value V2. Thus, LED 116 can be used to provide information to the user of card 1, for example, to indicate that card 1 is identifying the user's fingerprint by emitting light, or to sequence the acquisition of reference biometric data by a sensor, for example, during an enrollment phase.

[0062] According to one embodiment, the second operating phase of the card 1 corresponds to the control phase of the LED 116. During this second phase, no data is exchanged between the circuits 106 and 108, in particular via the conductor 110. Preferably, during this second phase, the card 1 does not communicate with the card reader. According to one embodiment, the circuit 108 is configured to implement a low-consumption mode, such as a standby mode, during the second operating phase, in which the circuit 108 is able to maintain the second voltage on the terminal 118.

[0063] In card 1, conductor 110 not only enables circuits 106 and 108 to communicate with each other during the first operating phase, but also enables control of LED 116 during the second operating phase. This is particularly advantageous because the number of inputs / outputs of circuit 100 (e.g. its microcontroller 106) is typically small and limited, e.g. less than or equal to 4.

[0064] Furthermore, despite the communication between circuits 100 and 108 via conductor 110 , the fact that circuit 108 is configured to apply the first voltage to its terminal 118 during the first phase enables LED 116 to be prevented from emitting light during the first operating phase.

[0065] The fact that the circuit 100 is configured to deliver the voltage Vdd at the value V1 during the first operating phase ensures correct operation of the sensor 112 and also consumes less energy than during the second phase in which the voltage Vdd is at the value V2 .

[0066] Figure 2 This diagram illustrates the method Figure 1 The timing diagram of the implementation method in the type of card. Figure 1 The implementation in card 1 is described as an example.

[0067] At step 200 (block "First phase"), circuit 100 of card 1 delivers voltage Vdd for powering circuit 108 and sensor 112 at value V1. During this step, circuit 108 delivers a first voltage on its terminal 118, so that LED 116 connected between terminal 118 and conductor 110 remains disconnected. Step 200 therefore corresponds to the Figure 1 The first stage of operation is described.

[0068] At the next stage 202 (block "End of first stage?"), circuits 100 and 108 verify whether the first operating stage is ended, or in other words, whether step 200 is ended. More specifically, circuits 100 and 108 determine whether a second operating stage must begin. As an example, only one of circuits 100 and 108 (preferably circuit 100) verifies whether the first stage is ended and then possibly notifies the other circuit.

[0069] If the first phase has not ended (output “No” of block 202 ), card 1 remains in the first operating phase, in which voltage Vdd is equal to V1 and the first voltage at terminal 118 .

[0070] If the first phase is finished and if the card 1 has to enter the second operating phase (output “yes” of block 202 ), the method is executed at step 204 (“second phase” block).

[0071] As an example, the entry into step 204 is determined by circuit 100 and indicated to circuit 108 by circuit 100, for example, via a specific signal transmitted on conductor 110. It is also possible that the entry into step 204 is determined by circuit 108 and indicated to circuit 108 by circuit 108, for example, via a specific signal transmitted on conductor 110. However, preferably, circuit 100 determines the entry into the second phase and indicates it to circuit 108. In practice, circuit 100 can synchronize the implementation of the second phase and the communication phase between card 1 and the card reader, so that the second phase is implemented when card 1 and the card reader are not communicating, thereby making it possible to limit the overall power consumption in the card.

[0072] At step 204, circuit 100 delivers voltage Vdd at value V2. In addition, circuit 108 applies a second voltage to its terminal 118. Thus, as previously described with respect to Figure 1 As described above, whether the LED 116 emits light is controlled by the voltage VC on the wire 110 .

[0073] At the next step 206 (block "Second phase ended?"), circuits 100 and 108 verify whether the second operating phase has ended, or in other words, whether step 204 has ended. More specifically, circuits 100 and 108 determine whether a new first operating phase must begin. For example, the end of the second phase is determined by circuit 100, which indicates the end of the second phase to circuit 102, for example due to a specific signal transmitted via conductor 110.

[0074] If the second phase has not ended (output “No” of block 206 ), card 1 remains in the second operating phase, in which voltage Vdd is equal to V2 and the second voltage on terminal 118 .

[0075] If the second phase is finished (“yes” output of block 206 ), the method continues, for example, with a new step 200 or a new first phase.

[0076] Figure 3 The timing diagrams of voltage Vdd, voltage VC, voltage V3 on terminal 118, and voltage VL across LED 116 are shown. Figure 2 The method is through Figure 1 An example of a card 1 implementation.

[0077] At time t0, card 1 is in the first operation phase ( Figure 2 Step 200, Figure 3 Thus, the voltage Vdd is at value V1 and the voltage V3 is zero.

[0078] In this example, at time t0, the voltage VC on the conductor 110 is equal to Vdd, ie, equal to V1. As a result, the voltage VL is negative and equal to -V1, and the LED 116 remains off.

[0079] At the next time t1 , the card 1 is still in the first operating phase and the voltage VC is switched to transmit a new bit, for example via the conductor 110 .

[0080] In this example, at time t1, voltage VC is switched to zero. As a result, voltage VL switches to zero, and LED 116 remains off.

[0081] At the next time t2 , the card 1 is still in the first operating phase and the voltage VC is switched to transmit a new bit, for example via the conductor 110 .

[0082] In this example, at time t2, the voltage VC on the conductor 110 is equal to Vdd, ie, equal to V1. As a result, the voltage VL is negative and equal to -V1, and the LED 116 remains off.

[0083] At the next time t3, the voltage VC is switched. In this example, at time t3, the voltage VC is switched to zero. As a result, the voltage VL is switched to zero, and the LED 116 remains off.

[0084] At the next time t4, one of the circuits 100 and 108, preferably with respect to Figure 2 The circuit 100 shown determines that the card 1 should switch to the second operating phase ( Figure 2 The output of step 202 is "yes") and notifies its other circuits.

[0085] According to one embodiment, entering the second operation phase from the first operation phase includes a synchronization phase, which includes the following steps: Figure 3 1-Z, conductor 110 is set to a high-impedance state. One of the terminals of LED 116 coupled to conductor 110 is then also in a high-impedance state. LED 116 thus remains off. For example, setting conductor 110 to a high-impedance state is controlled by circuit 100 and enables circuit 108 to be instructed that it may change the value of voltage V3 at terminal 118 without causing light emission from LED 116.

[0086] At the next time t5, the start of the second phase is marked ( Figure 2 Step 204, Figure 3 In the “second phase” of the control circuit 100, the circuit 100 sets the voltage Vdd to the value V2, and the circuit 108 sets the voltage V3 to the determined value so that the light emission of the LED 116 can be controlled by the voltage VC.

[0087] The anode of LED 116 is coupled to terminal 118 ( Figure 1 ), at time t5, circuit 108 therefore switches voltage V3 to voltage Vdd, or in other words, switches voltage V3 to value V2.

[0088] At the next time t6 , when the card 1 is in the second operating phase, the circuit 100 ends the high impedance state of the conductor 110 and switches the voltage VC to a zero value or to a voltage Vdd equal to V2 .

[0089] In this example, at time t6, voltage VC is switched to voltage Vdd, which is then equal to V2. Voltage VL is then zero, and LED 116 remains off.

[0090] At the next time t7 , the card 1 is still in the second operation phase, and the circuit 100 or the circuit 108 (circuit 100 in this example) controls the light emission phase of the LED 116 by switching the voltage VC.

[0091] In this example, at time t7, the circuit 100 switches the voltage VC to zero. As a result, the voltage VL is switched to a value V2 greater than the turn-on voltage Vth of the LED 116, and the LED 116 turns on.

[0092] At the next time t8, card 1 is still in the second operating phase, and circuit 108 and circuit 100 (circuit 100 in this example) turn off LED 116 by switching voltage VC to voltage Vdd in this example, which is equal to V2. As a result, voltage VL is switched to zero value, and LED 116 is turned off.

[0093] Figure 4 The diagram is shown very schematically in the form of a box. Figure 1 An alternative embodiment of card 1. Figure 4 Card 1 has the same Figure 1 The cards 1 share a large number of structural and functional elements, and only the differences between the two cards 1 are highlighted here.

[0094] Figure 4 Card 1 and Figure 1 Card 1 differs only in that the anode of LED 116 is coupled (eg, connected) to conductor 110 and its cathode is coupled (eg, connected) to terminal 118 of microcontroller 108 .

[0095] exist Figure 4In card 1, during the first operating phase, the first voltage applied by circuit 108 to terminal 118 is voltage Vdd, which is then equal to V1. Thus, when voltage VC is zero, voltage VL is negative and equal to -V1, so that LED 116 remains off, and when voltage VC is equal to voltage Vdd and therefore equal to V1, voltage VL is zero, so that LED 116 remains off. In summary, during the first operating phase, even if circuits 100 and 108 communicate via conductor 110, LED 116 remains off by switching voltage VC between zero and voltage Vdd.

[0096] exist Figure 4 In card 1, during the second operating phase, the first voltage applied by circuit 108 to terminal 118 is zero voltage. Therefore, when voltage VC is zero, voltage VL is zero, whereby LED 116 remains off, and when voltage VC is equal to voltage Vdd, and therefore equal to V2, value V2 of voltage VL is greater than turn-on threshold Vth of LED 116, whereby LED 116 emits light. In summary, during the second operating phase, light emission from LED 116 is controlled by switching voltage VC between zero value and voltage Vdd.

[0097] Figure 5 The diagram is shown very schematically in the form of a box. Figure 1 Another alternative embodiment of the card 1. Figure 5 Card 1 has the same Figure 1 The Card 1 shares a large number of structural and functional elements, and only the differences between the two Card 1s will be highlighted here.

[0098] exist Figure 5 , another conductor 110′ is shown coupling the circuit 100 (e.g., its microcontroller 106) to the circuit 108. The conductor 110′ (typically a wire) is preferably connected to a GPIO-type terminal of the circuit 100 or its microcontroller 106. Similar to the conductor 110, the conductor 110′ enables the circuits 100 and 108 to communicate with each other during a first operating phase by switching the voltage VC′ of the conductor 110′ between a zero value and a voltage Vdd.

[0099] Figure 5 Card 1 and Figure 1Card 1 of FIG108 differs in that it includes an additional LED 116′ having a first terminal (in this example, its cathode) coupled (e.g., connected) to the additional conductor 110′ and a second terminal (in this example, its anode) coupled (e.g., connected) to the terminal 118 of the circuit 108. The conduction threshold of LED 116′ may be different from the conduction threshold Vth of LED 116. However, the conduction threshold of LED 116′ is similar to the conduction threshold of LED 116 and is less than the value V2 of voltage Vdd.

[0100] Thus, during the second operating phase, LED 116′ can be controlled by voltage VC′ of conductor 110′ similarly to LED 116 controlled by voltage VC of conductor 110. Furthermore, during the first operating phase, LED 116′ remains off similarly to LED 116, with voltage VC′ being zero or equal to voltage Vdd.

[0101] According to one embodiment, LED 116 is configured to emit red light and LED 116 ′ is configured to emit green light.

[0102] In the aforementioned embodiments, implementations, and variations, for example:

[0103] The conduction threshold of LED 116 is equal to 1.8V;

[0104] The value V1 of the voltage Vdd is equal to 1.8V;

[0105] The sensor 112 is configured to be correctly powered with the voltage Vdd when the voltage Vdd is between a low value VL2 equal to 1.62 V and a high value VH2 equal to 1.98 V;

[0106] The value V2 of the voltage Vdd is equal to 2V;

[0107] The circuit 108 is configured to be properly powered using the voltage Vdd regardless of whether the voltage Vdd is at the value V1 or at the value V2; and

[0108] exist Figure 5 In the case of card 1, the conduction threshold of LED 116' is, for example, less than the conduction threshold of LED 116, for example, equal to 1.7V.

[0109] Various embodiments and variations have been described. Those skilled in the art will appreciate that certain features of these various embodiments and variations may be combined, and that other variations will occur to those skilled in the art. Specifically, with the anodes of LEDs 116 and 116' coupled to respective conductors 110 and 110' and their cathodes coupled to terminal 118, the combination is achieved. Figure 5The described card 1 will be within the capabilities of those skilled in the art.

[0110] Finally, based on the functional indications given above, the actual implementation of the described embodiments and variants is within the capabilities of a person skilled in the art.

Claims

1. A smart card comprising: a first circuit configured to deliver a supply voltage in response to supply power received by the smart card, the supply voltage having a first value during a first operating phase and a second value during a second operating phase; a second circuit coupled to the first circuit via an electrical conductor and configured to be powered by the supply voltage; as well as a light emitting diode having a first terminal coupled to the electrical conductor and a second terminal coupled to the first terminal of the second circuit; The second circuit is configured to, during the first operating phase, apply a first voltage to the first terminal of the second circuit to ensure that the light emitting diode is not illuminated regardless of the voltage present on the electrical conductor, and is further configured to, during the second operating phase, apply a second voltage to the first terminal of the second circuit, the second voltage allowing the light emitting diode to be selectively illuminated depending on the voltage present on the electrical conductor. 2 . The smart card of claim 1 , wherein the first circuit and the second circuit are configured for data communication via the electrical conductor during the first operating phase.

3. The smart card of claim 1 , wherein data communication is achieved during the first operating phase by causing the first circuit and the second circuit to switch a voltage on the conductor between zero and the first value of the supply voltage to indicate a data logic state.

4. The smart card of claim 3 , wherein at least one of the first circuit and the second circuit is configured to, during the second operating phase, switch the voltage on the conductor between the zero value and the second value of the power supply so as to cause selective illumination of the light emitting diode in connection with the communication of information to a user of the smart card. The smart card of claim 1 , wherein the second value of the supply voltage is greater than the first value of the supply voltage. 6 . The smart card of claim 1 , wherein the second value of the supply voltage is greater than a turn-on threshold of the light emitting diode, and wherein the first value of the supply voltage is less than the turn-on threshold of the light emitting diode. 7 . The smart card of claim 1 , wherein the second value of the supply voltage is less than a maximum supply voltage of the second circuit.

8. The smart card of claim 1, wherein the smart card further comprises a biometric sensor configured to be powered using the supply voltage delivered by the first circuit.

9. The smart card of claim 8, wherein the biometric sensor is a fingerprint sensor.

10. The smart card of claim 8, wherein the second circuit and the biometric sensor are configured to communicate with each other.

11. The smart card of claim 10 , wherein the biometric sensor is configured to operate with a supply voltage included in a range of values less than the second value and including the first value, the biometric sensor being further configured to withstand the supply voltage at the second value.

12. The smart card of claim 1 , wherein the first circuit is further configured to set the electrical conductor to a high impedance state to synchronize switching from the first voltage to the second voltage on the first terminal of the second circuit performed by the second circuit.

13. The smart card of claim 1, wherein the first terminal is an anode of the light emitting diode, the second terminal is a cathode of the light emitting diode, the first voltage is equal to the supply voltage at the first value, and the second voltage is zero.

14. The smart card of claim 1, wherein the first terminal is a cathode of the light emitting diode, the second terminal is an anode of the light emitting diode, the first voltage is zero, and the second voltage is equal to the supply voltage at the second value.

15. The smart card of claim 1 , further comprising an additional electrical conductor coupling the first circuit to the second circuit and an additional light emitting diode having a first terminal coupled to the additional electrical conductor and a second terminal coupled to the first terminal of the second circuit.

16. The smart card of claim 1, wherein the supply power is received via an electromagnetic field emitted by a card reader.

17. The smart card of claim 1, wherein the supply power is received via direct electrical contact between the smart card and a card reader.

18. A method of controlling a light emitting diode of a smart card, the 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 the first terminal of the second circuit, the method comprising the steps of: During the first operating phase: delivering, by the first circuit, a supply voltage at a first value in response to supply power received by the smart card; supplying power to the second circuit using the supply voltage; as well as 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 the voltage present on the electrical conductor; and During the second operational phase: delivering, by the first circuit, the supply voltage at a second value based on the supply power received by the smart card; supplying power to the second circuit using the supply voltage; as well as A second voltage is applied by the second circuit to the first terminal of the second circuit, the second voltage allowing the light emitting diode to be selectively illuminated depending on the voltage present on the electrical conductor.

19. The method according to claim 18, further comprising: During the first operating phase, data communication occurs between the first circuit and the second circuit via the electrical conductor.

20. The method of claim 19, wherein data communication during the first operating phase comprises: The voltage on the electrical conductor is switched between a zero value and the first value of the supply voltage by the first circuit and the second circuit.

21. The method according to claim 20, further comprising: During the second operating phase, the voltage on the electrical conductor is switched between the zero value and the second value of the supply voltage by at least one of the first circuit and the second circuit to cause selective lighting of the light emitting diode in connection with the communication of information to a user of the smart card.

22. The method of claim 18, wherein the second value of the supply voltage is greater than the first value of the supply voltage.

23. The method of claim 18, wherein the second value of the supply voltage is greater than a turn-on threshold of the light-emitting diode, and the first value of the supply voltage is less than the turn-on threshold of the light-emitting diode.

24. The method of claim 18, wherein the second value of the supply voltage is less than a maximum supply voltage of the second circuit.

25. The method of claim 18, further comprising: A biometric sensor of the smart card is powered using the supply voltage delivered by the first circuit.

26. The method according to claim 25, further comprising: Data communication is performed between the second circuit and the biometric sensor.

27. The method of claim 25, wherein the biometric sensor is configured to operate with a supply voltage included in a range of values less than the second value and including the first value, the biometric sensor further configured to withstand the supply voltage at the second value.

28. The method of claim 18, further comprising placing, by the first circuit, the electrical conductor into a high impedance state to synchronize switching, performed by the second circuit, from the first voltage to the second voltage at the first terminal of the second circuit.

29. The method of claim 18, wherein the first terminal is an anode of the light-emitting diode, the second terminal is a cathode of the light-emitting diode, the first voltage is equal to the supply voltage at the first value, and the second voltage is zero.

30. The method of claim 18, wherein the first terminal is a cathode of the light-emitting diode, the second terminal is an anode of the light-emitting diode, the first voltage is zero, and the second voltage is equal to the supply voltage at the second value.

31. The method of claim 18, wherein the smart card further comprises an additional electrical conductor coupling the first circuit to the second circuit and an additional light emitting diode having a first terminal coupled to the additional electrical conductor and a second terminal coupled to the first terminal of the second circuit.

32. The method of claim 18, further comprising receiving the supply power via an electromagnetic field emitted by a card reader.

33. The method of claim 18, further comprising receiving the supply power via direct electrical contact of the smart card with a card reader.

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