Driver circuits, corresponding devices, and systems

Abstract

The present disclosure relates to a drive circuit, a corresponding device, and a system. The drive circuit is for an airbag system and includes, for example, a differential transconductance amplifier having a first input node, a second input node, and an output node, the output node being coupled to the second input node via a feedback line; a transistor coupled between a drive node and a power supply node, the power supply node being configured to be coupled to a power source; a control node coupled to a control electrode of the transistor and the output node; a Zener diode arrangement having a cathode terminal and an anode terminal coupled to the power supply node and the first input node, respectively; a pull-up assembly arranged in parallel with the Zener diode arrangement; and an enable switch coupled to the first input node and referenced to ground, and the enable switch is switchable between a conducting state and a non-conducting state by the differential transconductance amplifier, the differential transconductance amplifier providing controlled discharge / charge of a current to the control node to turn the transistor on / off, respectively.

Description

Technical Field

[0001] This description relates to driver circuits. For example, one or more embodiments may be applied to controlling power transistors, such as power p-type metal-oxide-semiconductor logic (PMOS) transistors. Background Art

[0002] Power transistors are currently widely used in various devices, such as for example "intelligent" power devices in the automotive field.

[0003] A detonator driver device for an airbag system may be an example of such a device.

[0004] The name "detonator" is a name currently adopted in the automotive field, indicating a component used for ignition to initiate the airbag deployment process in an airbag inflator.

[0005] In certain applications, the detonator may be configured to generate an error code indicating that the associated airbag needs to be replaced. Summary of the Invention

[0006] Although driver circuits are highly active in this field, there is a need for driver circuits that can reduce electromagnetic radiation (EMI) (e.g., by reducing current peaks) and improve the safety level of associated devices.

[0007] The aim of one or more embodiments is to help provide such an improved circuit.

[0008] According to one or more embodiments, this aim can be achieved by means of a circuit having the features described in the following claims.

[0009] One or more embodiments may relate to corresponding devices, for example, a combination of a circuit such as one or more embodiments and a (power) transistor driven by this circuit.

[0010] One or more embodiments may relate to corresponding systems. An airbag system including a detonator driver according to an embodiment may be an example of such a system.

[0011] The claims are part of the technical teachings provided in respect of one or more embodiments.

[0012] The circuit according to an embodiment can advantageously be used as a switch configured to control the power supply to a transistor-based arrangement, such as a detonator driver.

[0013] One or more embodiments may be advantageous for controlling external PMOS transistors and / or limiting current peaks, thereby limiting electromagnetic radiation.

[0014] One or more embodiments can facilitate avoiding an undesired transistor turn-on (e.g., in the absence of detecting certain faults), thereby improving safety.

[0015] One or more embodiments can consider the fact that driving an external PMOS transistor can be advantageous compared to driving an external n-type MOS transistor (NMOS), because turning on the latter type of transistor may involve a higher voltage applied to the control terminal (gate, in the case of a field-effect transistor such as a MOS transistor), which may make the overall layout more complex and also increase the semiconductor area occupied.

[0016] One or more embodiments can employ a single-stage operational transconductance amplifier (OTA) with unit overall gain (buffer-like operation). Such an arrangement can involve a voltage limited by clamping the gate-source voltage (V GS ), and may also provide current limiting in the case of a short circuit to the ground or high-voltage (HV) node.

[0017] One or more embodiments can provide a high-voltage driver and an external transistor (e.g., PMOS) for driving. The so-called "third" FET in a detonator driver can be an example of such an application.

[0018] More generally, one or more embodiments can be applied to "intelligent" power applications, and a detonator driver is just one example among various possible applications.

[0019] One or more embodiments can involve one or more of the following features:

[0020] Performing p-gate voltage control using a charging or discharging process under controlled current conditions;

[0021] Performing self-limitation of current in the case of a short circuit to the ground (GND) or high-voltage (HV) node;

[0022] Limiting the gate-source voltage (V GS ) of the output stage;

[0023] Voltage clamping via a chain of Zener diodes;

[0024] Being able to turn off an external power transistor (e.g., PMOS) via a pull-up resistor or switch;

[0025] Limiting the current peak during the turn-on and turn-off phases; and

[0026] Unit gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] One or more embodiments will now be described by way of example only with reference to the accompanying drawings, in which:

[0028] Figure 1 is a circuit diagram illustrating an exemplary embodiment and external components that may be associated therewith;

[0029] Figure 2 is a circuit diagram of an exemplary embodiment that may be applied to a detonator driver arrangement; and

[0030] Figure 3 is a further circuit representation that is beneficial for understanding the operation of the embodiment. Detailed Description

[0031] One or more specific details will be set forth in the following description for the purpose of providing an in - depth understanding of example embodiments. These embodiments may be obtained without one or more of the specific details, or by other methods, components, materials, etc. In other instances, well - known structures, materials, or operations have not been shown or described in detail so as not to obscure certain aspects of the embodiments.

[0032] In the framework of this description, references to "an embodiment" or "one embodiment" are intended to indicate that a particular configuration, structure, or feature described in connection with that embodiment is included in at least one embodiment. Thus, phrases such as "in an embodiment" or "in one embodiment" that occur in one or more places in this description do not necessarily refer to the same embodiment. Furthermore, particular configurations, structures, or features may be combined in any suitable manner in one or more embodiments.

[0033] The reference numerals used herein are provided only for convenience and thus do not delimit the scope of protection or the scope of the embodiments.

[0034] In Figure 1 reference numeral 10 denotes a driver circuit as a whole, which is configured to operate using certain "external" components (i.e., devices that may be different from this embodiment).

[0035] For example, such external components may include a (power) transistor PT and a load A. In one or more embodiments, the load A may include a so - called detonator (illustrated as resistor Rsquib) in an airbag system.

[0036] As mentioned above, a "detonator" is a common name for a component within an airbag that is configured to initiate the airbag deployment process (and may generate an error code indicating the need to replace the airbag).

[0037] In this case, the transistor PT can be a so-called "third" transistor (a field effect transistor such as a MOS transistor, e.g., a PMOS transistor) included in such an airbag system. The name "third" transistor (third FET) is due to the following consideration: in such a possible application, the circuit 10 can include a detonator driver circuitry 12, and the detonator driver circuitry 12 includes "first" and "second" transistors 120, 122 that act as low-side (LS) and high-side (HS) transistors during the driving of the load A.

[0038] In one or more embodiments, the first and second transistors 120, 122 can in turn include field effect transistors such as NMOS transistors.

[0039] In Figure 1 In an example one or more embodiments, the circuit 10 can include a set of pins 101 to 105, such as:

[0040] 101: VMAIN pin, configured to facilitate sharing of the supply voltage Vsupply (e.g., 23.5V) on the supply rail between the circuit 10 and the power transistor PT (e.g., by coupling to the source of the supply rail);

[0041] 102: SO pin, configured to drive the control terminal of the power transistor PT (such as the gate of a field effect transistor of a PMOS transistor);

[0042] 103: SS pin, configured to couple the current path through the power transistor PT (such as the source-drain of a field effect transistor of a MOSFET transistor) to the current flow line to ground GND provided by the drive circuitry 12 (e.g., the detonator), the drive circuitry 12 including the first and second transistors 120, 122; as illustrated herein, this can be done by coupling the current path through the power transistor PT (e.g., at the drain) and the current path through the second transistor 122 (e.g., at the drain);

[0043] 104: HSO (high-side) pin, configured to couple the current path through the second high-side transistor 122 (on the side of the transistor 122 opposite the SS pin 103, e.g., at the source) to the first input node of the load A; and

[0044] 105: LSO (low-side) pin, configured to couple the current path through the first low-side transistor 120 (e.g., the drain) to the second input node of the load A, where the current path through the transistor 120 is referenced to ground GND on the side of the transistor 120 opposite the LSO pin 105 (e.g., at the source).

[0045] AsFigure 1 Illustratively, circuit 10 includes a differential stage such as operational transconductance amplifier (OTA) 14, which has an output node 140 coupled to pin 102, and thus the output node 140 is configured to be coupled to a control terminal of power transistor PT, and has a (negative) feedback line 142 that couples the output node 140 to one of the inputs of OTA 14 (e.g., the inverting input 144).

[0046] As illustratively shown herein, power is supplied to OTA 14 by coupling the OTA between ground GND and a supply rail Vsupply (substantially pin 101) (e.g., at 23.5V).

[0047] As Figure 1 Illustratively, another (e.g., non-inverting) input 146 of OTA 14 is configured to have a clamping voltage Vclamp applied thereto, and the clamping voltage Vclamp is provided at node A via a set of N zener diodes (collectively indicated as 16).

[0048] As Figure 1 Illustratively, the set of zener diodes is arranged in cascade, where the cathode of the zener diode faces the supply line or supply rail Vsupply, and its anode faces node A.

[0049] Reference numeral 18 denotes an electronic switch (e.g., a transistor such as a MOSFET transistor), which is arranged with a current path through the switch (i.e., the source-drain channel, assuming the switch is implemented by a field effect transistor), and the switch is coupled between node A and ground GND and is configured (in a manner known to those skilled in the art) to act as a current generator as illustratively shown at 18a.

[0050] Finally, reference numeral 20 denotes a pull-up component (such as a resistor), e.g., arranged between the supply rail Vsupply and node A (in the arrangement illustratively shown herein, which is also the non-inverting input 146 of OTA 14).

[0051] In Figure 1 the illustratively shown arrangement, since the set of zener diodes 16 is reverse-biased, node A (and thus the non-inverting input 146 of OTA 14) can be placed at a voltage Vclamp that is equal to the difference between the voltage at the supply line Vsupply and the zener voltage drop across the zener diodes 16.

[0052] If the N zener diodes have the same zener voltage Vzener, the relationship

[0053] Vclamp = Vsupply - N * Vzener

[0054] This will apply in these cases.

[0055] Figure 1 The operation of the arrangement illustrated in may involve applying an enable signal E (by means known to those skilled in the art, Figure 1 invisible in ) to the control electrode 180 (gate, in the case of implementation by a field effect transistor) of switch 18 to turn on the switch.

[0056] Since switch / MOSFET 18 is on, the Zener diode 16 will be (reverse) biased by the current generator 18a, such that the voltage Vclamp is applied to the (non-inverting) input 146 of the OTA 14.

[0057] This voltage will be transferred (at substantially about the same value) to the output node 140 of the OTA 14. Since 14 is an OTA, the output node will discharge under conditions of a controlled current, causing the (external) transistor PT to turn on (conduct).

[0058] In this way, the supply voltage at rail Vsupply (available to the power transistor PT via pin 101) will be applied to the squib driver circuitry 12.

[0059] Accordingly, there will be the possibility of activating (as required by the desired operating specification, via an activation signal AA generated in a manner known to those skilled in the art) transistors 120, 122 to power (energize) load A.

[0060] In an exemplary case of application to an airbag system, the signal AA may be an airbag activation signal AA generated (in a manner known per se, e.g., by a deceleration / collision detection system in the vehicle, invisible in the figure) to initiate the airbag deployment process by ignition.

[0061] Stopping the enabling of switch / MOSFET 18 (e.g., by placing the previously set "high" enable signal to "low") will cause the switch / MOSFET to turn off, and the non-inverting input 146 of the OTA 14 will be "pulled up" to the voltage of the supply rail Vsupply via component 20. Thus, with the (external) power transistor PT off (non-conducting), the voltage at the output node 140 (since 14 is an OTA, being charged under conditions of a controlled current) will be gradually placed at the voltage of the supply rail Vsupply.

[0062] In the embodiment illustrated herein, according to the desired application specification, the Zener voltage across the Zener diode arrangement 16 can be selected (e.g., by selecting the number N of cascaded Zener diodes) according to the overdrive value required to activate the (external) transistor PT.

[0063] In one or more embodiments, the pull-up resistor 20 may be replaced by a controlled switch (as shown by the dashed line at 20′) to reduce the turn-off time.

[0064] In Figure 2 and Figure 3 figures, components or classes of components or elements that have been discussed are denoted by like reference numerals, and thus will not be described in detail again for the sake of brevity. Figure 1 figures, components or classes of components or elements that have been discussed are denoted by like reference numerals, and thus will not be described in detail again for the sake of brevity.

[0065] Figure 2 and Figure 3 Certain “real-world” details of the circuit system illustrated in Figure 1 figures are illustrated by showing parasitic components (e.g., capacitance) and a power supply VS (e.g., a vehicle battery), with the power supply VS coupled to a supply rail Vsupply / supply pin 101 to provide a supply voltage (e.g., 23.5V) thereto.

[0066] Figure 3 The transistor-level representation in

[0067] figures further details certain components of the OTA 14 by highlighting the presence of a (negative) feedback path 142 from the output node 140 to the (inverting) input 144. Those skilled in the art will readily understand that different circuit configurations may be employed for these purposes (e.g., applying the inverted OTA output to the OTA non-inverting input). Figure 3 For completeness only,

[0068] figures illustrate possible diode provisions that are beneficial for protecting the circuit system (substantially pin 102) from electrostatic discharge phenomena (currently referred to as ESD - electrostatic discharge). Such phenomena may occur, for example, when handling the chip.

[0069]

[0070]

[0071]

[0072] The circuit illustrated herein (e.g., 10) may include:

[0072] A differential transconductance amplifier (OTA, such as 14), having a first input node (such as 146), a second input node (such as 144), and an output node (such as 140), the output node being coupled to the second input node via a feedback line (such as 142);

[0073] A power supply node (such as, 101) and a drive node (such as, 103), configured to be coupled to a current path through a transistor (such as, PT, optionally a field effect transistor such as a MOSFET transistor, such as a PMOS), the transistor being disposed between the power supply node and the drive node, the power supply node being configured to be coupled to a power supply (such as, VS at voltage Vsupply);

[0074] A control node (such as, 102), configured to be coupled to a control electrode (gate, in the case of a field effect transistor such as a MOSFET) of the transistor, the control node being coupled to the output node of the differential transconductance amplifier;

[0075] A Zener diode arrangement (such as, 16), having cathode and anode terminals coupled to the power supply node and the first input node of the differential transconductance amplifier;

[0076] A pull-up component (such as, 20, 20'), arranged in parallel with the Zener diode arrangement; and

[0077] An enable switch (such as, 18), coupled to the first input node of the differential transconductance amplifier, the enable switch being referenced to ground and switchable between the following two states (such as, see E):

[0078] i) A conducting state, the first input node of the differential transconductance amplifier being coupled to the power supply node via a reverse-biased Zener diode arrangement, and the differential transconductance amplifier providing a controlled current discharge to the control node coupled to the output node of the differential transconductance amplifier to turn on the transistor; and

[0079] ii) A non-conducting state, the first input node of the differential circuit stage being pulled up to the voltage of the power supply node (by the pull-up component), and the differential transconductance amplifier providing a controlled current charge to the control node coupled to the output node of the differential transconductance amplifier to turn off the transistor.

[0080] In the circuit illustrated herein, the output node and the second input node of the differential transconductance amplifier may be coupled via a negative feedback line.

[0081] In the circuit illustrated herein, the Zener diode arrangement may include a series arrangement of N Zener diodes, with their cathodes and anodes facing the power supply node and the first input node of the differential transconductance amplifier, respectively.

[0082] In the circuits illustrated herein, a pull-up component can include one of a pull-up resistor (e.g., 20) and a pull-up switch (e.g., 20'), the pull-up switch being configured to be turned on to couple a first input node of a differential circuit stage to a power supply node.

[0083] In the circuits illustrated herein, an enable switch can include a transistor having a current path therethrough (source-drain in the case of a field effect transistor such as a MOSFET), the transistor being configured to provide a current flow line (e.g., 18a) between a Zener diode arrangement and ground.

[0084] The circuits illustrated herein can include a load drive circuitry (e.g., 12, 120, 122) between the drive node and ground, the load drive circuitry being activatable (e.g., AA) since the drive node is connected to the power supply node via a transistor turned on by the enable switch in the on state.

[0085] In the circuits illustrated herein, the load drive circuitry can include:

[0086] a first (e.g., 104) output node and a second (e.g., 105) output node configured to be coupled to a load (e.g., A); and

[0087] a pair of transistors (e.g., 120, 122) arranged such that one transistor (e.g., 122) is between the drive node and the first output node and the other transistor (e.g., 120) is between the second output node and ground.

[0088] The devices illustrated herein can include:

[0089] the circuits illustrated herein; and

[0090] the transistor having a current path therethrough coupling the power supply node and the drive node.

[0091] The systems illustrated herein can include:

[0092] the devices illustrated herein; and

[0093] a load (e.g., A) coupled across the first and second output nodes.

[0094] In the systems illustrated herein, the load coupled to the first and second output nodes includes an activation component (e.g., "detonator") of a vehicle airbag.

[0095] Without prejudice to the basic principles, details and embodiments may vary relative to what is described only by way of example without departing from the scope of protection.

[0096] The various embodiments described above may be combined to provide further embodiments. These and other changes may be made to the embodiments in light of the above detailed description. In general, in the following claims, the terms used should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be construed to include all possible embodiments and the full scope of equivalents to which these claims are entitled. Accordingly, the claims are not limited by the present disclosure.

Claims

1. A circuit, comprising: A differential transconductance amplifier having a first input node, a second input node, and an output node, the output node being coupled to the second input node via a feedback line; A power supply node and a drive node configured to be coupled to a transistor, the transistor operative to provide a current path between the power supply node and the drive node, the power supply node being configured to be coupled to a power source; A control node coupled to the output node of the differential transconductance amplifier and the control terminal of the transistor; A Zener diode arrangement having a cathode coupled to the power supply node and an anode coupled to the first input node of the differential transconductance amplifier; A pull-up component coupled in parallel with the Zener diode arrangement; And An enable switch having a first terminal coupled to the first input node and a second terminal coupled to a ground node, the enable switch being switchable between two states: A conducting state, during which the first input node is coupled to the power supply node via the Zener diode arrangement in a reverse-biased configuration, and the differential transconductance amplifier performs a controlled current discharge of the control node to turn on the transistor; And A non-conducting state, during which the first input node is pulled up to the power supply node via the pull-up component, and the differential transconductance amplifier performs a controlled current charge of the control node to turn off the transistor.

2. The circuit according to claim 1, wherein the feedback line is a negative feedback line.

3. The circuit according to claim 1, wherein the Zener diode arrangement includes a plurality of Zener diodes coupled in series and having the same polarity, such that a first Zener diode of the plurality of Zener diodes has an anode coupled to the first input node, a last Zener diode of the plurality of Zener diodes has a cathode coupled to the power supply node, and one or more intermediate Zener diodes of the plurality of Zener diodes are coupled between the first Zener diode and the last Zener diode and have the same polarity as the first Zener diode and the last Zener diode.

4. The circuit according to claim 1, wherein the pull-up component includes at least one of: a pull-up resistor, or a pull-up switch configured to be placed in a conducting state to couple the first input node to the power supply node.

5. The circuit according to claim 1, wherein the enable switch includes a switching transistor operative to have a current path therethrough providing a current flow line between the Zener diode arrangement and the ground node.

6. The circuit according to claim 1, comprising: A load drive circuitry coupled between the drive node and the ground node, the load drive circuitry being operable to be activated in response to an enable switch in a conducting state and the transistor being turned on to couple the drive node to the power supply node.

7. The circuit according to claim 6, wherein the load drive circuit system comprises: a first output node and a second output node, configured to be coupled to a load; and a first transistor having a first conduction terminal coupled to the intermediate drive node and a second conduction terminal coupled to the first output node; and a second transistor having a first conduction terminal coupled to the second output node and a second conduction terminal coupled to the ground node.

8. An apparatus for a driver circuit, comprising: a circuit, comprising: a differential transconductance amplifier having a first input node, a second input node, and an output node, the output node being coupled to the second input node via a feedback line; a power supply node and a drive node, configured to be coupled to a transistor that operates to provide a current path between the power supply node and the drive node, the power supply node being configured to be coupled to a power supply; a control node coupled to the output node of the differential transconductance amplifier and the control terminal of the transistor; a Zener diode arrangement having a cathode coupled to the power supply node and an anode coupled to the first input node of the differential transconductance amplifier; a pull-up component coupled in parallel with the Zener diode arrangement; and an enable switch having a first terminal coupled to the first input node and a second terminal coupled to the ground node, the enable switch being switchable between two states: a conducting state, during which the first input node is coupled to the power supply node via the Zener diode arrangement in a reverse-biased configuration, and the differential transconductance amplifier performs a controlled current discharge of the control node to turn on the transistor; and a non-conducting state, during which the first input node is pulled up to the power supply node via the pull-up component, and the differential transconductance amplifier performs a controlled current charge of the control node to turn off the transistor; and the transistor is arranged with the current path passing therethrough, the current path coupling the power supply node and the drive node.

9. The apparatus according to claim 8, wherein the Zener diode arrangement comprises a plurality of Zener diodes coupled in series and having the same polarity, such that the first Zener diode of the plurality of Zener diodes has an anode coupled to the first input node, the last Zener diode of the plurality of Zener diodes has a cathode coupled to the power supply node, and one or more intermediate Zener diodes of the plurality of Zener diodes are coupled between the first Zener diode and the last Zener diode and have the same polarity as the first Zener diode and the last Zener diode.

10. The apparatus according to claim 8, wherein the pull-up component comprises at least one of: a pull-up resistor, or a pull-up switch configured to be placed in a conducting state to couple the first input node to the power supply node.

11. A system for a driver circuit, comprising: a circuit, comprising: A differential transconductance amplifier having a first input node, a second input node, and an output node, the output node being coupled to the second input node via a feedback line; A power supply node configured to be coupled to a power source; A drive node; A transistor having a first conducting terminal coupled to the power supply node, a second conducting terminal coupled to the drive node, and a control terminal, the transistor operating to provide a current path between the power supply node and the drive node; A control node coupled to the output node of the differential transconductance amplifier and the control terminal of the transistor; A Zener diode arrangement having a cathode coupled to the power supply node and an anode coupled to the first input node of the differential transconductance amplifier; A pull-up component coupled in parallel with the Zener diode arrangement; An enable switch having a first terminal coupled to the first input node and a second terminal coupled to a ground node, the enable switch being switchable between two states: A conducting state, during which the first input node is coupled to the power supply node via the Zener diode arrangement in a reverse-biased configuration, and the differential transconductance amplifier performs a controlled current discharge of the control node to turn on the transistor; and A non-conducting state, during which the first input node is pulled up to the power supply node via the pull-up component, and the differential transconductance amplifier performs a controlled current charge of the control node to turn off the transistor; A load drive circuit system including: A first circuit output node and a second circuit output node; and A first load transistor having a first conducting terminal coupled to the intermediate drive node and a second conducting terminal coupled to the first circuit output node; and a second load transistor having a first conducting terminal coupled to the second circuit output node and a second conducting terminal coupled to the ground node; and A load coupled to the first circuit output node and the second circuit output node.

12. The system of claim 11, wherein the load includes an activation component of a vehicle airbag.

13. The system of claim 11, wherein the feedback line is a negative feedback line.

14. The system of claim 11, wherein the Zener diode arrangement includes a plurality of Zener diodes coupled in series and having the same polarity, such that a first Zener diode of the plurality of Zener diodes has an anode coupled to the first input node, a last Zener diode of the plurality of Zener diodes has a cathode coupled to the power supply node, and one or more intermediate Zener diodes of the plurality of Zener diodes are coupled between the first Zener diode and the last Zener diode and have the same polarity as the first Zener diode and the last Zener diode.

15. The system according to claim 11, wherein the pull-up component includes at least one of the following: a pull-up resistor, or a pull-up switch configured to be placed in a conducting state to couple the first input node to the power supply node.

16. The system according to claim 11, wherein the enable switch includes a switching transistor operative to have a current path therethrough that provides a current flow line between the Zener diode arrangement and the ground node.

17. A method for a driver circuit, comprising: operating a switch to set a first voltage to either a clamping voltage representing a difference between a supply voltage and a voltage drop across a Zener diode arrangement, or a pull-up voltage pulled up to the supply voltage; receiving the first voltage at a first input via a differential transconductance amplifier; receiving a feedback voltage at a second input via the differential transconductance amplifier, the feedback voltage representing an output voltage provided at an output of the differential transconductance amplifier; comparing, via the differential transconductance amplifier, the first voltage and the feedback voltage; and based on the comparison, absorbing or supplying a control current at the output via the differential transconductance amplifier to operate a transistor in a conducting state or a non-conducting state.

18. The method according to claim 17, wherein the feedback line between the output and the second input is a negative feedback line.

19. The method according to claim 17, wherein the Zener diode arrangement includes a plurality of Zener diodes coupled in series and having the same polarity.

20. The method according to claim 17, comprising: pulling up the pull-up voltage to the supply voltage via a pull-up component, the pull-up component including at least one of the following: a pull-up resistor or a pull-up switch.

21. The method according to claim 20, comprising: placing the pull-up switch in a conducting state to pull the first voltage to the supply voltage.

22. The method according to claim 17, wherein the switch includes a switching transistor operative to have a current path therethrough that provides a current flow line between the Zener diode arrangement and the ground node.

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