NFC Controller

Abstract

NFC Controller This description relates to an NFC controller comprising a first node (NVBAT) configured to be connected to a battery; a second node (NVDD_TX) configured to receive a regulated voltage from an external DC-DC converter connected to said first node; a third node (RF01, RF02) configured to be connected to a radio frequency output of the NFC controller; said third node being configured, in a first mode, to be connected to either the first node or the second node, and, in a second mode, to either the first node or both the first and second nodes. Figure for the abbreviation: Fig. 2

Description

Title of the invention: NFC Controller technical field

[0001] This description relates generally to NFC controllers. Previous technique

[0002] In NFC controllers, an amplifier (transmitter power amplifier, PA) is used between the power source (e.g., a battery) and an antenna to control the transmitted power. In order to reduce the size of the antenna or increase the transmitted power, an amplified voltage can be supplied to the amplifier (usually referred to as PA) by a DC-DC boost converter.

[0003] Furthermore, NFC controllers must supply a certain voltage to the antenna even in the off mode. Unfortunately, in this mode, DC-DC boost controllers usually operate by lowering their output level to 0 (bucking). Conventional NFC controllers therefore require a dedicated DC-DC converter that can handle a high impedance at its output (High Z) in the off mode. Summary of the invention

[0004] There is a need to offer NFC controllers that are compatible with non-dedicated DC-DC converters.

[0005] One embodiment overcomes all or part of the disadvantages of known NFC converters.

[0006] One embodiment provides an NFC controller comprising: a first node configured to be connected to a battery; a second node configured to receive a regulated voltage from an external DC-DC converter connected to said first node; at least one third node configured to be connected to a radio frequency output of the NFC controller; said third node being configured to, in a first mode, be connected either to the first node or to the second node, and, in a second mode, either to the first node or to the first and second nodes.

[0007] According to one embodiment, the first node is an active mode and the second mode is an off mode.

[0008] According to one embodiment, the third node is configured, in the first mode, to be connected either to the first node, or to the first and second nodes depending on the battery voltage level.

[0009] According to one embodiment, the third node is configured, in the second mode, to be connected either to the first node, or to the first and second nodes depending on an active state of the DC-DC converter.

[0010] According to one embodiment, the NFC controller includes a selection circuit configured to connect or disconnect the first and second nodes depending on said active state of the DC-DC converter.

[0011] According to one embodiment, the selection circuit is configured to apply a voltage corresponding to the maximum between a voltage present at the first node and the regulated voltage at a biasing node.

[0012] According to one embodiment, the selection circuit comprises a first bypass circuit comprising a transistor having a first conduction node connected to the first node and a second conduction node connected to the second node.

[0013] According to one embodiment, the selection circuit comprises a second bypass circuit in parallel with the first bypass circuit, the second bypass circuit comprising a transistor having a first conduction node connected to the first node and a second conduction node connected to the second node via a resistor.

[0014] According to one embodiment, a control signal for the gate of the transistor of the first and second bypass circuits depends on the active state of the DC-DC converter and on a comparison between the voltages on the first and second nodes.

[0015] According to one embodiment, said control signal further depends on an activation state of the DC-DC converter.

[0016] According to one embodiment, the control signal of the first bypass circuit further depends on an activation state of the radio frequency output of the NFC controller.

[0017] According to one embodiment, a region of the transistor body of the first and second bypass circuits is configured to be connected to the biasing node.

[0018] According to one embodiment, the selection circuit comprises third and fourth transistors which have their sources connected to the bias node and their drains connected to the first and second nodes, respectively, a control signal for the third and fourth transistors being configured to depend on a comparison between the voltages on the first and second nodes.

[0019] According to one embodiment, the NFC controller includes a first voltage regulator connecting the first node to the third node depending on the active state of the DC-DC converter.

[0020] According to one embodiment, the NFC controller includes a second voltage regulator connecting the second node to the third node, a first conduction node of the second voltage regulator being connected to second node, a second conduction node of the second voltage regulator being connected to the third node, and a control node and a body region of the second voltage regulator being connected to the bias node.

[0021] One embodiment provides an electronic circuit comprising the controller as described above and an antenna connected to said third node. Brief description of the drawings

[0022] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0023] Fig. 1 represents an electronic circuit according to an example;

[0024] [Fig.2] represents an NFC controller according to one embodiment;

[0025] [Fig. 3] represents a circuit of the NFC controller of [Fig. 2] according to a mode of lisation;

[0026] [Fig. 4] represents a circuit of the NFC controller of [Fig. 2] according to another embodiment; and

[0027] [Fig.5] represents a summary table of the operation of the circuit of [Fig.4], Description of the implementation methods

[0028] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0029] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been represented and are detailed.

[0030] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or linked through one or more other elements.

[0031] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0032] Unless otherwise specified, the expressions "approximately", "about", "meaning- "Suitably" and "of the order of" mean to within 10%, preferably to within 5%.

[0033] Fig. 1 represents an electronic circuit 101 according to an example.

[0034] The electronic circuit 101 includes a DC-DC converter 102 (DCDC) connected, or preferably linked, to an NVBAT node, to which a battery voltage VBAT is supplied for example, and providing a regulated voltage at an output node VOUT.

[0035] The DC-DC converter 102 is, for example, a step-up DC-DC converter.

[0036] The electronic circuit 101 also includes an NFC controller 104 which is connected, or preferably linked, on the one hand to the NVBAT node and, on the other hand, to the output node VOUT.

[0037] The NFC 104 controller is further connected, or preferably linked, to an NFC 106 antenna (NFC Antenna).

[0038] The NFC controller includes a power amplifier (not shown in [Fig. 1]). The power emitted by means of the antenna is controlled by a voltage supplied to the input of the power amplifier and by the antenna impedance.

[0039] In one example, the DC-DC converter provides a voltage at the input of the power amplifier to implement a smaller antenna and increase TX transmit power.

[0040] In the example shown, other circuits 108, 110 (Other ICs) are connected to the output of the DC-DC converter 102. Sharing the DC-DC converter between the NFC controller and other applications minimizes the total number of coils on a platform and the total footprint of the printed circuit board.

[0041] Sharing the DC-DC converter between the NFC controller and other applications presents problems. Indeed, in off-modes, i.e., when the electronic circuit is deactivated, NFC applications require the NFC controller's power amplifier to remain powered by a voltage, for example, the battery voltage in low-power mode, because the electronic circuit can be reactivated by the presence of an electromagnetic field. This implies that, for NFC applications in off-modes, the DC-DC converter should maintain a high-impedance output (High Z), in other words, connected to the battery. But, at the same time, in off-mode, other circuits 108, 110 are assumed to be off, which is usually achieved by setting the DC-DC converter to 0.In other words, with a classic NFC controller, it is not possible to simultaneously share the same DC-DC converter between an NFC controller and other circuits 108, 110.

[0042] The following embodiments provide a different NFC controller comprising The first node is powered by the NVBAT battery voltage; a second node is connected, or preferably linked, to the output of the DC-DC converter 102; and a third node is configured to be connected to a radio frequency output of the NFC controller, which is, for example, connected, or preferably linked, to the antenna. The third node is configured, in a first mode, to be connected to either the first node or the second node, and, in a second mode, to either the first node or both the first and second nodes.

[0043] Such an NFC controller allows the simultaneous use of the same DC-DC converter by an NFC controller and other circuits 108, 110. Also, such an NFC controller allows the use of a DC-DC converter lowered to 0 as the power supply for the NFC controller.

[0044] Fig. 2 represents an NFC 104 controller according to one embodiment.

[0045] In the example shown, the NFC 104 controller includes the NVBAT node which is configured to be connected, or preferably linked, to a battery or a voltage supply.

[0046] The NFC controller 104 further includes the second node (NVDD_TX), which is connected, or preferably linked, to the output of the DC-DC converter and which is configured to receive a regulated voltage from the DC-DC converter 102. The DC-DC converter 102 is, for example, external or internal to the NFC controller.

[0047] An active state of the DC-DC converter is reported, for example, in a bit (NEVER_TIED_TO_GND). When NEVER_TIED_TO_GND=0, the output of the DC-DC converter can be lowered to 0. When NEVER_TIED_TO_GND=1, the output of the DC-DC converter is fixed in a high impedance mode (high Z), for example by being pulled towards or above the battery voltage.

[0048] In the example shown, the NFC controller further includes a selection circuit 210 (Smart Bypass) configured to connect or disconnect the NVBAT node from the second NVDD_TX node depending on the active state (NEVER_TIED_TO_GND) of the DC-DC converter and also depending, for example, on a comparison between the VDD_TX voltage at the output of the DC-DC converter and the battery voltage VBAT.

[0049] The selection circuit 210 is further configured to apply a voltage (VHIGH), corresponding to the maximum between the battery voltage VBAT present at the node NVBAT and the regulated voltage VDD_TX present at the second node NVDD TX, to a biasing node (NVHIGH).

[0050] The NFC 104 controller includes an NFC 202 amplifier (NFC PA) having, for example, two input nodes NVDD_ASK and NVDD_RF respectively connected, or Preferably connected to ground via a first capacitor 260 and a second capacitor 270. A single input node could be considered by a person skilled in the art. The NFC 202 amplifier, for example, has one or two outputs at nodes RF01 and RF02, depending on the number of inputs. Nodes RF01 and RF02 are radio frequency nodes configured, for example, to be connected, or preferably connected, to antenna 106. The NFC 202 amplifier includes, for example, impedance matching and signal amplification circuits.

[0051] The NFC controller 104 further includes a first voltage regulator 206 (LDO VBAT) that connects or disconnects the battery node NVBAT and the nodes RF01, RF02 depending on the active NEVER_TIED_TO_GND state of the DC-DC converter. For example, the first regulator 206 is configured to connect NVBAT to RF01 when the DC-DC converter 102 is in a NEVER_TIED_TO_GND=0 mode.

[0052] The first voltage regulator 206 comprises one or more power transistors 205 (Power), for example PMOS transistors, having their control portions and body region 207 (Amp+Ctrl) connected, or preferably connected, to the bias node NVHIGH in order to prevent leakage of P+ / Nwell diodes formed in the body region of the PMOS transistors. According to one example, a first conduction node of a transistor of the first voltage regulator 206 is connected to the second node NVDD_TX and a second conduction node of the first voltage regulator 206 is connected to the nodes RF01 and RF02 via a weak pull-up resistor and to the node NVDD_RF.

[0053] The NFC 104 controller further includes, for example, a second voltage regulator 230 (LDO RF) connecting the second NVDD_TX node to the RF01 and RF02 nodes via the NVDD_RF node. The second voltage regulator 230 includes, for example, one or more power transistors 234 (Power), for example PMOS transistors, having their control portions and body region 232 (Amp+Ctrl) connected, or preferably connected, to the bias node NVHIGH. According to one example, a first conduction node of a transistor of the second voltage regulator 230 is connected to the second NVDD_TX node and a second conduction node of the second voltage regulator is connected to the RF01 node via a high-resistance resistor and via the NVDD_RF node.

[0054] In the case of amplitude modulation, the amplifier has two radio frequency nodes RF01 and RF02. The NFC 104 controller further includes an optional third voltage regulator 240 (LDO ASK) connecting the second node NVDD_TX to the voltage VDD_TX at nodes RF01 and RF02 via the NVDD_ASK node. The third voltage regulator 240 includes, for example, one or several power transistors 244 (Power), for example PMOS transistors, having their control and body regions 232 (Amp+Ctrl) connected, or preferably connected, to the bias node NVHIGH. As an example, a first conduction node of a transistor in the third voltage regulator is connected to the second node NVDD_TX, and a second conduction node of the second voltage regulator is connected to the RF02 node via the NVDD_ASK node.

[0055] Figure 3 represents a circuit of the NFC 104 controller of Figure 2 according to a mode of implementation. More precisely, [Fig.3] represents the selection circuit 210 of [Fig.2] according to one embodiment.

[0056] In the example shown, the selection circuit 210 includes a first bypass circuit 380 (High power bypass). The first bypass circuit 380 includes a transistor 370, for example a PMOS, having one conduction node connected to the first node NVBAT and another conduction node connected to the second node NVDD_TX.

[0057] A body region of transistor 370 is configured to be connected to the NVHIGH bias node.

[0058] A control signal for the gate of transistor 370 of the first bypass circuit is provided by a circuit 360 which takes as input a signal including for example the active state NEVER_TIED_TO_GND of the DC-DC converter.

[0059] Another input of circuit 360 is, for example, configured to receive a comparison signal, provided by circuit 310, which is at VDD_TX when the voltage present on node NVDD_TX is greater than the voltage at the first node NVBAT, and at VBAT when VDD_TX <VBAT.

[0060] Another input of the circuit 360 is for example configured to receive the inverse signal 350 of a signal (DCDC_ENABLE) which includes one or more bits which indicate whether the DC-DC converter 102 is activated or not.

[0061] An additional input to the 360 ​​circuit is a signal (RF SUB System activated) comprising one or more bits that are related to an operating state of the NFC amplifier 202. An example of an operating state of the NFC amplifier is, for example, a communication state in which data is being received or transmitted. In other words, in this communication state, the RF SUB System activated bit is, for example, representative of an activation state of the RF01 and RF02 radio frequency outputs of the NFC controller. Another example of an operating state of the NFC amplifier is, for example, a standby, or low-power, state in which the NFC amplifier 202 can be woken up by a magnetic field arriving from another NFC device.

[0062] Circuit 360 is configured to perform a NOT AND function on these four signals. If all the signals at the input of circuit 360 are high, then the The output signal will be at a low level, which activates transistor 370 and consequently short-circuits nodes NVBAT and NVDD_TX (if transistor 370 is a PMOS transistor). If one of the signals feeding circuit 360 is low, then the output signal remains high, blocking transistor 370 from conducting.

[0063] In the example shown, the selection circuit 210 comprises third 320 and fourth 330 transistors having their sources connected, or preferably connected, to the bias node NVHIGH and their drains connected, or preferably connected, to the first and second nodes NVBAT, NVDD_TX, respectively.

[0064] The body regions of the third and fourth transistors 320, 330 are connected, or preferably linked, to the bias node NVHIGH.

[0065] A control node of the third transistor 320 is connected, or preferably connected, to the output of the comparator 310, and a control node of the fourth transistor 330 is connected to the output of the comparator 310 via an inverter circuit 336. When VDD_TX > VBAT, the fourth transistor 330 is in a conducting state and the third transistor 320 is in a non-conducting state. When VDD_TX <VBAT, le troisième transistor 320 est dans un état de conduction et le quatrième transistor 330 est dans un état de non-conduction.

[0066] As an example, the third and fourth transistors 320 and 330 are PMOS transistors, which allows for a lower impedance value than an NMOS transistor (Vgs is greater for a high Vd). In order to have an impedance similar to an NMOS, Vg should be greater than the voltage VHIGH.

[0067] Figure 4 represents an alternative embodiment of the NFC controller circuit of Figure 2. More specifically, Figure 4 represents the selection circuit 210 of Figure 2 in an alternative embodiment. The example in Figure 4 is similar to the example in Figure 3, except that the selection circuit further includes a second bypass circuit 480 (low-power bypass) in parallel with the first bypass circuit 380.

[0068] The second bypass circuit 480 includes for example a transistor 470 having a first conduction node connected to the NVBAT node and a second conduction node connected to the second NVDD_TX node via a resistor 490 having a typical resistance of 100 Ohms to 1 kOhms, for example 150 Ohms.

[0069] A gate control signal for transistor 470 is provided by a circuit 460 which has inputs similar to those of circuit 360 of the first bypass circuit 380, except that the RF SUB System activated input is not connected to the inputs of circuit 460.

[0070] In the example of [Fig. 4], depending on the operating mode of the NFC 202 amplifier as specified in the "RF SUB System activated" bit, the The first and / or second bypass circuits will be selected. In communication mode, the first bypass circuit 380 will be activated, and in standby mode, the second bypass circuit 480 will be activated and the first bypass circuit 380 will be deactivated. In this case, during startup, transistor 470 is switched off first, before transistor 370. Resistor 490 ensures a gradual rise in the VDD_TX voltage and prevents any destructive current from flowing.

[0071] Figure 5 represents a summary table of the operation of the circuit in Figure 4. The columns of the table represent the values ​​taken by the NEVER_TIED_TO_GND bit, the result of the VDD_TX>VBAT operation, the RF SUB System activated bit, the DCDC_EN bit indicating whether the DC-DC converter 102 is activated or not, a state of transistor 470 (LOW POWER SWITCH VBAT-VDDTX), a state of transistor 370 (HIGH POWER SWITCH VBAT-VDDTX), and the values ​​of the voltages present at the NVHIGH node, respectively.

[0072] The following configurations are implemented while the first regulator 206 is configured to link NVBAT to RF01 and RF02 when the DC-DC converter 102 is in a roll-down mode to 0 (NEVER_TIED_TO_GND=0).

[0073] In a first configuration, the NEVER_TIED_TO_GND bit is set to 0, VDD_TX <= VBAT, the RF SUB System activated bit is set to 0 or 1, and the DCDC_EN bit is set to 0 or 1. As a result, transistors 370 and 470 are in an open state, meaning they act as a switch in a non-conducting state, and VHIGH = VBAT. In this configuration, the NVBAT and NVDD_TX nodes are not connected. VBAT is supplied, for example, to amplifier 202 via the first voltage regulator 206, for instance, for detecting another NFC device if the RF SUB System activated bit is set to 0, or for communication if the RF SUB System activated bit is set to 1.

[0074] In a second configuration, the NEVER_TIED_TO_GND bit is set to 0 or 1, VDD_TX > VBAT, the RF SUB System activated bit is set to 0 or 1, and the DCDC_EN bit is set to 0 or 1. As a result, transistors 370 and 470 are in an open state, and VHIGH = VDD_TX. In this second configuration, if NEVER_TIED_TO_GND is set to 0, the NVBAT and NVDD_TX nodes are not connected. In this case, VBAT is supplied, for example, to amplifier 202 via the first voltage regulator 206, for example, for the detection of another NFC device.

[0075] In a third configuration, the NEVER_TIED_TO_GND bit is set to 1, VDD_TX=VBAT, the RF SUB System activated bit, and the DCDC_EN bit are set to 0. As a result, transistor 470 is in an open state, transistor 370 is closed (meaning it is equivalent to a switch in a conduction configuration), and VHIGH=VBAT. In this configuration, NVBAT is connected, or of The NVBAT node is therefore connected to the second voltage regulator 230 via resistor 490, for example, to power amplifier 202 in off mode.

[0076] In a fourth configuration, the NEVER_TIED_TO_GND bit is set to 1, VDD_TX=VBAT, the RF SUB System activated bit is set to 1, and the DCDC_EN bit is set to 0. As a result, transistors 370 and 470 are in a closed state, and VHIGH=VBAT. In this configuration, the NVBAT and NVDD_TX nodes are connected without resistance, and VBAT is supplied to amplifier 202 via the second voltage regulator 230, for example, for detecting or communicating with another NFC device.

[0077] In a fifth configuration, the NEVER_TIED_TO_GND bit is set to 1, VDD_TX <vbat, le bit rf sub system activated et dcdc_en sont fixés à 1. il en résulte que les transistors 370 470 dans un état ouvert vhigh="VBAT." dans cette cinquième configuration, nœuds nvbat nvdd_tx ne pas connectés. ce cas nœud est par exemple relié l'amplificateur 202 l'intermédiaire du premier régulateur de tension 206.

[0078] The selection device 210 automatically adapts the type of connection (connected / linked, or disconnected) between the NVBAT and NVDD_TX nodes based on the active state (high impedance, High Z, or pulled down) of the DC-DC converter 102, the state of the NFC amplifier 202 (active communication or standby), and the power supply modes (battery or DC-DC enabled) of the NFC system.

[0079] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will be apparent to those skilled in the art. In particular, the third voltage regulator 240 is optional and is used, for example, for amplitude modulation. The NFC controller could be implemented without the regulator 240 in the case of on / off modulation with a power amplifier 202 having a single radio frequency output RF01.

[0080] In summary, the different configurations of the selection device 210 and the first voltage regulator 206 lead to different modes of operation.

[0081] In a mode where the DC-DC converter 102 is fixed at High Z, the NVBAT and NVDD_TX nodes are not short-circuited and the first voltage regulator 206 is in an open position. In this mode, the NFC amplifier 202 is, for example, in an active mode and the RF01 output is supplied by a current generated by the DC-DC converter 102 and the second voltage regulator 230.

[0082] In another mode where the DC-DC converter 102 is fixed at High Z, the NVBAT and NVDD_TX nodes can be connected via the device selection 210. In this mode, the NFC amplifier 202 is, for example, in an active mode and the RF01 and RF02 outputs are powered by a current generated by the battery and then passing through the NVBAT node and the second voltage regulator 230.

[0083] In another mode, where the DC-DC converter 102 is fixed in a mode lowered to 0, the NVBAT and NVDD_TX nodes are disconnected by the selection device 210. In this mode, the NFC amplifier 202 is for example in an active mode and the RF01 and RF02 outputs are powered by a current generated by the battery then passing through the NVBAT node and the first voltage regulator 206.

[0084] In another mode, where the DC-DC converter 102 is fixed in a mode lowered to 0, the NVBAT and NVDD_TX nodes are disconnected by the selection device 210. In this mode, the NFC amplifier 202 is for example in an off mode and the RF01 output is biased by the battery by means of the low pull-up of the first voltage regulator 206.

[0085] In another mode, where the DC-DC converter 102 is fixed in the high impedance mode High Z, the NVBAT and NVDD_TX nodes are connected by means of the selection device 210. In this mode, the NFC amplifier 202 is for example in an off mode and the RF01 and RF02 outputs are biased by the battery by means of the NVBAT node and the second voltage regulator 230.

[0086] Finally, the practical implementation of the described embodiments and variants is within the grasp of a person skilled in the art, based on the functional specifications given above. In particular, additional branch circuits could be arranged in parallel with the first and second branches and with a resistor having a different resistance value than resistor 490 in order to adapt the low-power operation.

[0087] A person skilled in the art will be able to adapt circuits 360 and / or 460 and their incoming inputs if they wish to implement transistors 370 and / or 470 as NMOS transistors. In this case, the function of circuit 360, 460 should be an AND function.

Claims

Demands

1. NFC controller comprising: a first node (NVBAT) configured to be connected to a battery; a second node (NVDD_TX) configured to receive a regulated voltage from a DC-DC converter external to the NFC controller and connected to said first node; at least a third node (RF01, RF02) configured to be connected to a radio frequency output of the NFC controller; said third node being configured, in a first mode, to be connected alternately to either the first node or the second node, and, in a second mode, alternately to either the first node or to the first and second nodes connected together.

2. Controller according to claim 1, wherein the first mode is an active mode and the second mode is an off mode.

3. Controller according to claim 1 or 2, wherein the third node is configured to, in the second mode, be connected either to the first node, or to the first and second nodes depending on the battery voltage level.

4. Controller according to any one of claims 1 to 3, wherein the third node is configured to, in the second mode, be connected either to the first node, or to the first and second nodes depending on an active state (NEVER_TIED_TO_GND) of the DC-DC converter.

5. Controller according to claim 4, wherein the NFC controller includes a selection circuit (210) configured to connect or disconnect the first and second nodes depending on said active state (NEVER_TIED_TO_GND) of the DC-DC converter.

6. Controller according to claim 5, wherein the selection circuit (210) is configured to apply a voltage (VHIGH) corresponding to the maximum between a voltage present at the first node (VBAT) and the regulated voltage (VDD_TX) at a bias node (NVHIGH).

7. Controller according to claim 5 or 6, wherein the selection circuit (210) comprises a first bypass circuit (380) comprising a transistor (370) having a first conduction node connected to the first node (NVBAT) and a second conduction node connected to the second node (NVDD_TX).

8. Controller according to claim 7, wherein the selection circuit (210) includes a second bypass circuit (480) in parallel with the first bypass circuit (380), the second bypass circuit including a transistor (470) having a first conduction node connected to the first node (NVBAT) and a second conduction node connected to the second node (NVDD_TX) via a resistor (490).

9. Controller according to claim 8, wherein a gate control signal of the transistor of the first and second bypass circuits depends on the active state (NEVER_TIED_TO_GND) of the DC-DC converter and a comparison between the voltages on the first and second nodes.

10. Controller according to claim 9, wherein said control signal further depends on an enable state (DCDC_ENABLE) of the DC-DC converter.

11. Controller according to claim 9 or 10, wherein the control signal of the first bypass circuit further depends on an activation state of the radio frequency output of the NFC controller.

12. Controller according to any one of claims 8 to 11 in their dependence on claim 6, wherein a transistor body region of the first and second bypass circuits is configured to be connected to the bias node (NVHIGH).

13. A controller according to claim 12, wherein the selection circuit (210) comprises third (320) and fourth (330) transistors having their sources connected to the bias node (NVHIGH) and their drains connected to the first and second nodes (NVBAT, NVDD_TX), respectively, a control signal for the third and fourth transistors being configured to depend on a comparison between the voltages (VBAT, VDD_TX) on the first and second nodes

14. Controller according to any one of claims 4 to 13, wherein the NFC controller includes a first voltage regulator (LDO VBAT) connecting the first node to the third node depending on the active state (NEVER_TIED_TO_GND) of the DC-DC converter.

15. A controller according to any one of claims 6 or 7 to 14 in their dependence on claim 6, wherein the NFC controller comprises a second voltage regulator (LDO RF) connecting the second node to the third node, a first conduction node of the second voltage regulator being connected to the second node, a second conduction node of the second voltage regulator being connected to the third node, and a control node and a body region of the second voltage regulator being connected to the bias node (NVHIGH).

16. Electronic circuit comprising the controller according to any claims 1 to 15 and an antenna connected to said third node.

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