Micropower magnetic switches

Abstract

Sensor (10) with: a circuit generating a magnetic field signal (20); and a control circuit (52) coupled to the magnetic field signal generating circuit (20) and responding to an externally generated trigger signal (54) to trigger the generation of a supply current pulse (80), wherein the supply current pulse (80) activates the magnetic field signal generating circuit (20) for a predetermined time interval; a sensor input (50) configured to receive a pulsed signal generated by an external trigger signal generator as the externally generated trigger signal (54); and wherein The predetermined time interval is determined by the control circuit.

Description

AREA OF INVENTION

[0001] This invention relates generally to magnetic field sensors and in particular to magnetic field sensors for use in low-power applications. BACKGROUND OF THE INVENTION

[0002] Magnetic field sensors for detecting a magnetic field in low-power applications are known. Such sensors typically use an internal timing circuit arrangement to activate sections of the device for a small percentage of the duty cycle.

[0003] DE 197 04 782 C2 discloses a magnetic field detector and a method for detecting a magnetic field. A low-power magnetic field detector comprises a magnetic field voltage converter, e.g., a Hall effect sensor or a field plate bridge. The converter includes a converter voltage amplifier, or alternatively, the input of a separate converter voltage amplifier can be connected to the output of the converter. The detector further comprises a zero-crossing comparator, which is designed to generate a binary signal with a voltage level when the comparator input signal has a polarity, and vice versa. In addition, a clockable flip-flop, the input of which is connected to the output of the comparator, and a free-running clock unit, which is connected to the converter for chopping the converter's excitation current, are provided.The clock unit is connected to the flip-flop to allow the flip-flop to capture and store the binary comparator output signal at a specific time at the end of each converter excitation period. An addition circuit has one output connected to the comparator input and a second input connected to the amplifier output. A positive feedback device connected between the flip-flop output and the second output of the addition circuit is designed to generate a predetermined bias voltage at the second input of the addition circuit with a specific polarity only when the stored binary output signal of the comparator has that specific voltage level.The addition circuit serves to generate a voltage that corresponds to the sum of the converter output voltage and the predetermined bias voltage, and to apply the sum voltage to the input of the comparator in order to make the comparator a Schmitt comparator that has hysteresis with memory-covering clock period ranges when the Hall element is not excited.

[0004] The method for detecting a magnetic field whose field strength is greater than a predetermined field strength includes providing a magnetic field voltage converter, providing a zero-crossing comparator with a binary output signal composed of one and another voltage level corresponding to a positive and a negative comparator input signal, and periodically clocking and activating the converter only for a first part of each clock period.

[0005] DE 698 32 475 T2 discloses a magnetometer with a coil and magnetic core of high permeability. The magnetometer is provided with a driver circuit having a voltage-controlled output and a reset device, a sensor with a core made of elongated material with high magnetic permeability having a central longitudinal axis and a multiple winding of electrically conductive wire wound around the core along its longitudinal axis and electrically insulated from the core, the sensor being connected at a first end of the winding to the voltage-controlled output of the driver circuit, a measuring circuit connected to the sensor, a comparator circuit with a voltage reference, an input connected to a second end of the winding and an output connected to the reset device of the driver circuit, and is characterized in particular by…that the driver circuit applies a voltage to the sensor and the comparator output becomes active, wherein the driver circuit is reset when the voltage at the comparator input equals the reference voltage, generating an output pulse train, and the measuring circuit determines the vector component of a local magnetic field in the direction of the central long axis of the core as a function of the pulse width of the output pulse train.

[0006] Patent DE 29 21 546 A1 discloses an arrangement for detecting field strengths emanating from a field generator by means of a Hall generator, characterized in that pulse-shaped signals are provided for controlling the Hall generator, with an arbitrary pulse repetition frequency at constant field and a pulse repetition frequency at least twice as high as the highest frequency of a field strength change occurring in the useful signal at changing field, and that the duty cycle of the pulses is selected such that the pulse energy content of a pulse is equal to or less than the effective control power of the Hall generator.

[0007] US patent 2008 / 0048772A1 discloses a sensor circuit comprising a sensor section that receives information about an object to be measured or detected as an electrical signal, and a control circuit that controls the operation of the sensor section. The control circuit receives an externally applied start input signal so that the sensor section operates only for a specific duration after the start input signal is applied. This configuration makes it possible to reduce power consumption by arbitrarily controlling the period of intermittent operation of the sensor circuit.

[0008] The object of the present invention is to provide a micro power magnetic switch which is configured to control power consumption, thereby reducing the overall power consumption.

[0009] This problem is solved by the features of claims 1, 10 and 19. Further advantageous embodiments and developments are the subject of the subsequent claims. SUMMARY OF THE INVENTION

[0010] In one aspect, the invention is generally directed to a sensor. The sensor comprises a magnetic field signal generating circuit and a control circuit that is coupled to the magnetic field signal generating circuit and responds to an externally generated trigger signal to initiate a supply current pulse that activates the magnetic field signal generating circuit for a predetermined time interval.

[0011] Exemplary embodiments of the invention may have one or more of the following features. The sensor may further include a magnetic field signal processing circuit coupled to the control circuit and the magnetic field signal generating circuit. The magnetic field signal processing circuit is activated by the supply current pulse to set a state for an output signal based on an output signal from the magnetic field signal generating circuit. The sensor may be provided with an input configured to receive a pulsed signal generated by an external control as the externally generated trigger signal. Alternatively, the sensor may have a voltage supply input and be configured to use a pulsed power supply signal, based on a supply signal received at the voltage supply input, as the externally generated trigger signal.The control circuit can include a one-shot circuit to receive the externally generated trigger signal as a trigger input signal and, in response, provide a one-shot output pulse. The control circuit can further include a switch connected to the one-shot circuit, which can be operated to provide the supply current pulse in response to the one-shot output pulse of the magnetic field signal-generating circuit.

[0012] In another aspect, the invention relates to a system comprising a controller and a sensor coupled to the controller. The sensor includes a magnetic field signal generating circuit and a control circuit coupled to the magnetic field signal generating circuit, which responds to an externally generated trigger signal. The control circuit is operable to initiate a supply current pulse that activates the magnetic field signal generating circuit for a predetermined time interval. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The preceding features of the invention, as well as the invention itself, can be more fully understood from the following detailed description of the drawings. They show: Fig. 1 an exemplary low-power sensor having a single-pulse circuit configured to receive an external control signal as a single-pulse trigger input signal; Fig. 2 an alternative exemplary low-power sensor having a single-pulse circuit configured to use a supply (VCC) signal as a single-pulse trigger input signal; Fig. Three different sensor signal waveforms for low-power operation; and Fig. 4 an exemplary application in which a low-power sensor, such as the one used in Fig. 1-2 is shown, is used. DETAILED DESCRIPTION

[0014] Referring to Fig. Figure 1 shows a low-power sensor 10 that uses an externally generated signal to control its internal power consumption. A low-power sensor is one that is suitable for use in applications with limited power, such as battery-powered devices. In an embodiment as shown in Figure 1, the sensor is a low-power sensor 10 that uses an externally generated signal to control its internal power consumption. Fig. As shown in Figure 1, the sensor 10 is an output switching type of a magnetic field sensor. This type of sensor incorporates devices such as sensor switches (both unipolar and omnipolar, i.e., pole-dependent) and latches. In a magnetic field detection application, the sensor 10 is positioned near a magnetic device and provides a sensor output signal 14 at a sensor output (VOUT) 12, indicating the presence of a magnetic field of a predetermined strength. The sensor 10 can be movable or fixed relative to the magnetic device.

[0015] The sensor 10 comprises a magnetic field sensing element (hereinafter referred to as a magnetic field transducer) 16, which provides a magnetic field signal 18, for example, a voltage signal, proportional to the detected magnetic field. The sensing element 16 can be a single magnetically responsive element or, alternatively, two or more such elements arranged in various configurations, e.g., a half-bridge or full (Wheatstone) bridge. In the illustrated embodiment, the sensing element 16 is shown as a single Hall-effect element. However, the sensor 10 can be any type of sensor and is therefore not limited to the one described in the figure. Fig. The Hall-effect sensor shown in Figure 1 is limited. The element or elements of the sensing element 16 can therefore take a different form than that of a Hall-effect element, such as a magnetoresistance (MR) element. An MR element can be made from any type of MR device, including, but not limited to, an anisotropic magnetoresistance (AMR) device, a giant magnetoresistance (GMR) device, and a tunneling magnetoresistance (TMR) device with a magnetic tunnel junction (MTJ, also known as spin-dependent tunneling or SDT).

[0016] The sensing element 16 is shown within a magnetic field signal generating circuit 20, which may contain various conventional circuits operating to jointly generate the magnetic field signal 18. In addition to the sensing element 16, the circuit 20 generally includes at least one amplifier 22 for amplifying the output signal of the sensing element 16. The circuit 20 may implement chopper stabilization, whereby a supply voltage is alternately connected to contacts of the Hall effect element by a modulation switch circuit, and the modulated signal is then demodulated by the amplifier to provide the magnetic field signal without an offset voltage associated with the semiconductor Hall effect elements.Furthermore or alternatively, the circuit 20 can implement an offset matching feature by which the magnetic field signal is centered within the power supply range of the sensor, and / or a gain matching feature by which the gain of the magnetic field signal is adjusted to maximize peak-to-peak gain within the supply range without causing clipping.

[0017] The sensor 10 further comprises a magnetic field signal processing circuit 24 and an output circuit 26. The output circuit 26 is shown to include a latch 27 and an output stage 28. The circuit 24 is shown to include a low-pass filter 30 and a comparator circuit 32, which processes the magnetic field signal 18 to generate a comparator output signal 34. The comparator output signal 34 is supplied to the latch 27. The latch 27 buffers the state of the comparator output signal 34 in response to this signal. The output signal of the latch 27, a latch output signal 36, is supplied to the output stage 28, which serves to supply the sensor output signal 14 to the sensor output 12. The output stage 28 can be implemented as a totem-pole circuit.The output stage can alternatively be implemented as a current source output structure that provides two current levels, representing two digital output states of the sensor. Since the output current is supplied on the supply / ground lines, the use of a current source output structure eliminates the need for the voltage output signal 12.

[0018] To achieve low-power operation, sensor 10 can be activated for a first time interval and deactivated for a second time interval. Power is applied to specific sections of sensor 10 during the first time interval (or "wake intervals") and removed from these sections during the second time interval (or "standby intervals"). The measurement and subsequent processing that occurs during the wake intervals are referred to here as "sampling," and thus the wake intervals can alternatively be referred to as "sampling intervals" or "sampling times."

[0019] Further referring to Fig. 1 A control circuit or device 38 is provided to couple a power supply voltage VCC 40, supplied by an external power supply at a VCC terminal or input 42, to the circuits 20, 24, as shown, via a first VCC bus 44. A single-pulse output pulse or control signal 46 is applied to the control circuit 38. In the exemplary embodiment, as shown in Fig. As shown in Figure 1, the control circuit 38 is provided by a switch. The switch can be, for example, a transistor, such as a MOSFET device, or another type of switching device. The switch 38 is closed (or turned on) to supply power to the circuits 20 and 24 when the control signal 46 is at a first signal level (e.g., a logic high level), and open (or turned off) to remove power from the circuits 20 and 24 when the control signal is at a second signal level (e.g., a logic low level).

[0020] As in the illustrated embodiment of Fig. As shown in Figure 1, the sensor 10 has a second control circuit provided by a pulse circuit 48. The pulse circuit, or second control circuit 48, is coupled between a sensor input 50 and the switch 38. It is also coupled to ground via a capacitor 51. The switch 38 and the second control circuit 48, together with the capacitor 51, form a larger control circuit 52. The pulse circuit 48 is a device with a stable state that, in response to an input signal, changes the state of its output signal for a period of time before returning to the stable state. More precisely, it responds to an input "transition," that is, it is triggered by an edge. It can be designed for triggering on a rising edge (active high transition) or a falling edge (active low transition).A dual-trigger input capability can be provided to allow the end user to choose between triggering on a rising or falling edge. The single-pulse circuit 48 generates a single-pulse output pulse as the control signal 46, which follows a specific transition (or edge) of an externally generated trigger signal 54 received at the sensor input 50.

[0021] The trigger signal 54 can be a type of control signal, for example, a pulsed or clocked signal. This signal is supplied to the sensor 10 at sensor input 50 by an external trigger generator (e.g., a controller or processor) to which the sensor 10 is coupled in an application. The trigger signal 54 thus causes the control circuit 52 to activate a measurement and processing ("a sampling") during the wake interval. That is, the triggering activates the circuit 20 to generate a magnetic field signal and the processing circuit 24 to use this magnetic field signal to set the output state, which is temporarily stored by the latch 27 at the beginning of the following rest interval. In particular, the single-pulse circuit 48 generates an output pulse, the control signal 46, to turn on the switch 38, which in turn generates a supply current (ICC) pulse.The single-pulse circuit 48 generates a single output pulse at each triggering event, regardless of whether it is a rising or falling edge of the input signal. The control circuit 52 thus initiates an ICC pulse according to a timer, for example, a predetermined frequency set by an external trigger generator. Circuits 20 and 24 remain in idle mode (drawing only a small amount of quiescent current) until another single-pulse output pulse 46 is applied to switch 38 to activate circuits 20 and 24 for operation in a new wake / sample interval.

[0022] The ICC pulse has at least a predetermined minimum duration, corresponding to the wake or sampling interval. The single-pulse output pulse duration (and therefore the ICC pulse duration) is determined by values ​​of an internal timing input of the single-pulse circuit 48 and the capacitor 51. For correct operation, the sensor 10 requires a suitably timed ICC pulse. The control circuit 52 must therefore be designed to provide the minimum time required by the sensor's circuits 20 and 24 to generate a valid sample. The trigger signal 54 could be smaller or larger than the resulting ICC pulse. As is known in the art, the single-pulse circuit 48 can be provided with additional pulse control in the form of a reset and / or clear function, allowing the pulse duration to be extended or reduced as needed.A retrigger can be used to keep the sensor device operating in a full-power mode (in a 100% duty cycle), if desired.

[0023] The choice of capacitor for capacitor 51 can be made according to the time constraints and other possible application requirements. For example, it could be the type of structure described in U.S. Patent Application No. 12 / 198,191, entitled "Methods and Apparatus for Integrated Circuit Having Integrated Energy Storage Device," filed on August 28, 2008, by inventors William P. Taylor, Karl P. Scheller, and Andrea Foletto, and transferred to Allegro Microsystems, Inc., the agent of the present application. Although a capacitor is shown in the figure, the use of other types of energy storage devices, such as inductors, is also conceivable.

[0024] Output stage 28 provides the sensor output signal 14 with a first signal level when a magnetic product is within a predetermined distance of the sensor, and with a second signal level when the magnetic product is not within a predetermined distance of the sensor 10. Latch 27 is in operation to buffer the state of the comparator output signal 34 on the falling edge of each current pulse, corresponding to the end of each watch interval. Latch 27 and output stage 28 are directly coupled to VCC via a second VCC bus 56. An internal circuit arrangement of sensor 10 is connected to ground via a GND terminal 58.

[0025] The sensor 10 can be implemented as an integrated circuit (IC), which contains a semiconductor substrate on which various circuit elements are formed. The interface of such an IC is indicated by dashed lines in the figure and has at least one pin each to correspond to the sensor input pin 50, the VCC input or terminal 42, the GND terminal 58, and, depending on the output stage implementation, the output (VOUT) 12. It is evident that the functionality of the IC, that is, the circuit elements contained within it, can be varied to suit a specific application.

[0026] Referring to Fig. Figure 2 uses an alternative example of sensor 10, shown as sensor 10', where VCC is the single-pulse trigger signal. In an implementation as shown in Fig. As shown in Figure 2, the sensor 10' can have a pulse (or waveform) control device 60 between the VCC 40 and the pulse circuit 48. In such an implementation, a pulsed supply voltage signal is provided to the pulse circuit 48 as a pulse trigger signal 62. The pulse control device 60 can be a pulse-generating circuit, which, for example, includes another pulse circuit, a capacitor, or an inductor to couple the power supply voltage 40 to the input of the pulse circuit 48. In yet another implementation, the VCC 40 can be directly connected to the input of the pulse circuit. The design and / or implementation of the control device 60 in the sensor 10' depends on the characteristics of the VCC 40 supplied at the VCC terminal 42.Several applications are known to supply a pulsed (or toggling) VCC to the sensor as its supply voltage via an external battery-saving circuit. Other applications may use a constant supply voltage. There are, of course, methods for developing a single-pulse circuit with a forced signal-fire start state. As mentioned above regarding sensor 10, which is in... Fig. As shown in Figure 1, the output stage 28 in the sensor 10' can be implemented as a current source output structure. In a current source output structure implementation, as mentioned earlier, a current output signal is provided between the VCC and GND terminals. This type of output stage can make the sensor 10' more attractive for use in applications requiring a 2-wire interface for a wiring harness with less complexity.

[0027] Fig. Figure 3 shows illustrative signal waveforms 70 for a low-power sensor operation based on a trigger signal, as described above with reference to Fig. 1 - 2 is described. Referring to Fig. 1 - 3 show waveforms 70 and a waveform 72, which corresponds to the trigger signal 54 ( Fig. 1) or the single-impulse trigger signal 62

[0028] ( Fig. 2) corresponds to a waveform 74 corresponding to the comparator output signal 34, a waveform 76 corresponding to VCC 40, and a waveform 78 corresponding to the supply current ICC. It is obvious that in an example where VCC 40 is supplied directly to the single-pulse circuit input, as described above with reference to Fig. As explained in Section 2, the trigger signal waveform is also the VCC waveform. In the example shown, the timing sequence for a sampling operation begins with the trigger signal (waveform 72), which transitions to a high level. Responding to this transition, the single-pulse circuit 48 generates an output pulse to close (or open) the switch 38. The switch 38 then generates a supply current (or ICC) pulse 80. The supply current pulse 80 corresponds to the supply current delivered to the circuits 20 and 24 during a sampling interval 82. The sampling interval 82 defines the period in which a magnetic field strength measurement is taken and processed (as described above). The sampling interval 82 ends when the state of the comparator output signal 34 (waveform 74) is updated, which is shown here as a transition to a high level.This means that the illustrated example is based on a magnetic field level associated with a change in the output signal. At the end of the sampling interval 82, the supply current transitions from a waking current value to a quiescent current value and remains at this level until another ICC pulse is initiated by the next rising trigger edge. The output data generated during the sampling period is buffered on the falling edge of the current pulse and held until the next sampling occurs.

[0029] A typical ICC current during the sampling / wake interval can be approximately 1.5 mA. During the "standby" interval, a typical ICC standby current can be less than 75 nA. The current drawn by the low-power mode during the standby interval is therefore a considerable reduction in power compared to the power consumed during the wake interval. An end user, after determining how often measurements need to be updated for a given application, can set the wake-up rate of sensor 10 (or 10') to the minimum allowed by the application, thus extending the period during which circuits 20 and 24 are in standby mode (and thus reducing power consumption).

[0030] As mentioned above, with reference to Fig. 2. The output stage must be adapted for a 2-wire configuration. In the 2-wire configuration, with a pulsed VCC trigger, when the output signal transitions to a high current state (assuming sensor 10' receives an adequate magnetic signal), it remains in this state until the sensor is re-powered and the next sampling occurs. Otherwise, the output signal remains in the low current output state.

[0031] This low-power tripping method for automatic on / off control of a low-power operation can be applied to any type of digital output switching sensor, including switches and latches. It can also be used with other types of sensors, such as sensors with internal architectures (circuits 20, 24, 26) adapted for linear and current-sensing applications. In particular, some current-sensing applications, such as industrial or home power monitoring applications, may not require instantaneous current measurement. Taking current measurements at sampling times according to the low-power tripping method may be more than adequate.To support such operation, it may be desirable to include, in or as part of the output structure 26 for the sensor 10, 10', which operates as a current sensor, an analog-to-digital converter to generate a digital representation of an analog current level, and latches to retain this digital representation. The low-power sampling method is useful for any sensor design requiring low sampling rates and sampling times that are independent of an internal clock.

[0032] The 10, 10' sensor can be used in a wide range of low-power end-user applications. It is particularly attractive for battery-powered devices such as mobile (cellular and cordless) phones, portable media players, handheld gaming devices, mobile PCs (including pagers, palmtops or handheld computers, personal digital assistants, and the like), as well as for industrial measurement and as a replacement for a mechanical switch (e.g., a reed switch). Reducing power consumption extends the availability of battery-powered functions and also allows for a reduction in battery size and weight.In mobile phone applications, the low-power sensor 10, 10' can be used in particular for an open / closed lid detection scheme, which is operational to switch on when the lid is open and off when, for example, the lid is closed. This type of operation can be applied to other battery-powered devices with a lid / cover, e.g., a digital camera or a camera phone.

[0033] Fig. Figure 4 shows a simplified representation of an application 90 that uses the sensor 10 (or sensor 10') for low-power detection. The application 90 includes a trigger generator, shown as a microcontroller or processor 92, coupled to the sensor 10. The sensor 10 is located in close proximity to a magnetic flux source 94, shown as a magnetic device 94 located in a target section (“target”) 96 of the application. The magnetic flux source 94 can, of course, be any device or structure that generates a magnetic flux in a given magnetic field-sensing application. It can be implemented to include a permanent magnet, such as a ring magnet or a two-pole magnet. This magnet can be coupled to or mounted within a “target” device, that is, an object to be detected, such as a moving or rotating device.Other possible sources of magnetic flux may include electromagnets (e.g., current-carrying wire conductors and coils), such as those used in current-sensing applications, magnet / coil assemblies, and other current-carrying devices that generate magnetic fields.

[0034] The processor 92 supplies the sensor 10 and in particular the pulse circuit 48 (from Fig. 1-2) the trigger signal 54. The sensing element 16 of the sensor 10 detects a magnetic field 98 associated with the magnetic product 94 and subsequently generates the sensor output signal 14. In the application shown, the output signal 14 is supplied to the processor 92 (but can instead be supplied to another device). The controller or a power source can alternatively be supplied with a VCC signal (which the sensor uses as a VCC 40 trigger signal or a single-pulse trigger signal 62 of the VCC, as in Fig. 2 is shown, to generate, used) supply.

[0035] In a flip phone with an open or closed lid (or cover) detection scheme, as discussed above, the magnetic device 94 can be located in the cover (corresponding to the target section 96), and the sensor 10 and the microcontroller 92 can be located in the phone's base. In such an arrangement, the output signal 14, based on whether a magnetic field of a predetermined strength is detected, indicates whether the cover is open or closed.

[0036] All references cited herein are incorporated herein by reference in their entirety.

[0037] Since the preferred embodiments of the invention have been described, it is now obvious to those skilled in the art that other embodiments incorporating its concepts may be used. It is therefore assumed that these embodiments should not be limited to disclosed embodiments, but rather should only be limited by the spirit and scope of the appended claims.

Claims

[1] Sensor (10) with: a circuit generating a magnetic field signal (20); and a control circuit (52) coupled to the magnetic field signal generating circuit (20) and responding to an externally generated trigger signal (54) to trigger the generation of a supply current pulse (80), wherein the supply current pulse (80) activates the magnetic field signal generating circuit (20) for a predetermined time interval; a sensor input (50) configured to receive a pulsed signal generated by an external trigger signal generator as the externally generated trigger signal (54); and wherein The predetermined time interval is determined by the control circuit. [2] Sensor (10;) according to claim 1, further comprising a magnetic field signal processing circuit (24) coupled to the control circuit (52) and the magnetic field signal generating circuit (20), wherein the magnetic field signal processing circuit (24) is activated by the supply current pulse (80) to set a state for an output signal (14) based on an output signal (18) from the magnetic field signal generating circuit (20). [3] Sensor (10) according to claim 1, further comprising an input (50) configured to receive trigger signal (54) generated by an external microcontroller (92) as the externally generated trigger signal. [4] Sensor (10;) according to claim 1, wherein the magnetic field signal generating circuit (20) has a sensing element (16) which has at least one Hall effect element. [5] Sensor (10;) according to claim 1, wherein the magnetic field signal generating circuit (20) has a sensing element (16) comprising at least one magnetoresistance (MR-; MR = magnetoresistance) element. [6] Sensor (10;) according to claim 1, wherein the control circuit (52) has a single-pulse circuit (48) to receive the trigger signal (54;) as a trigger input signal and to provide a single-pulse output pulse (46) in response thereto. [7] Sensor (10;) according to claim 6, wherein the control circuit (52) further comprises a switch (38) connected to the single-pulse circuit (48) which is operable to supply the supply current pulse (80) to the magnetic field signal generating circuit (20) in response to the single-pulse output pulse (46). [8] Sensor (10;) according to claim 1, wherein the supply current pulse (80) defines a wake interval during which the magnetic field signal generating circuit (20) is activated, and the time between the supply current pulse (80) and a next supply current pulse (80) defines a sleep interval during which the magnetic field generating circuit (20) is deactivated. [9] Sensor (10;) according to claim 1, wherein the magnetic field signal generating circuit (20) and the control circuit (52) are integrated as an integrated semiconductor circuit. [10] System (90) with: a microcontroller (92); a sensor (10) coupled to the microcontroller (92), wherein the sensor (10) comprises a magnetic field signal generating circuit (20) and a control circuit (52) coupled to the magnetic field signal generating circuit (20) and responding to an externally generated trigger signal (54), wherein the control circuit (52) is operable to trigger the generation of a supply current pulse (80) by responding to the trigger signal (54), wherein the supply current pulse (80) activates the magnetic field signal generating circuit (20) for a predetermined time interval; and with a sensor input (50) configured to receive a pulsed signal generated by an external trigger signal generator as the externally generated trigger signal (54), wherein The predetermined time interval is determined by the control circuit. [11] System (90) according to claim 10, wherein the sensor (10;) further comprises a magnetic field signal processing circuit (24) coupled to the control circuit (52) and the magnetic field signal generating circuit (20), wherein the magnetic field signal processing circuit (24) is activated by the supply current pulse (80) to set a state for an output signal (14) based on an output signal (18) from the magnetic field signal generating circuit (20). [12] System (90) according to claim 10, wherein the controller comprises a microcontroller (92) and the sensor (10) further comprises a sensor input (50) configured to receive a trigger signal (54) generated by the microcontroller (92) as the externally generated trigger signal. [13] System (90) according to claim 10, wherein the magnetic field signal generating circuit (20) has a sensing element (16) which has at least one Hall effect element. [14] System (90) according to claim 10, wherein the magnetic field signal generating circuit (20) has a sensing element (16) comprising at least one magnetoresistive element. [15] System (90) according to claim 10, wherein the control circuit (52) has a single-pulse circuit (48) to receive the trigger signal (54;) as a trigger input signal and to deliver a single-pulse output pulse (46) in response thereto. [16] System (90) according to claim 15, wherein the control circuit (52) further comprises a switch (38) which is connected to and operable with the single-pulse circuit (48) to supply the supply current pulse (80) to the magnetic field signal generating circuit (20) in response to the single-pulse output pulse (46). [17] System (90) according to claim 10, wherein the supply current pulse (80) defines a wake interval during which the magnetic field signal generating circuit (20) is activated, and the time between the supply current pulse (80) and a next supply current pulse (80) defines a rest interval during which the magnetic field generating circuit (20) is deactivated. [18] System (90) according to claim 10, wherein the magnetic field signal generating circuit (20) and the control circuit (52) are integrated as an integrated semiconductor circuit. [19] Sensor (10) with: a sensor input (50) configured to receive a pulsed signal generated by an external trigger signal generator as the externally generated trigger signal (54) which has pulses; a circuit generating a magnetic field signal (20); and a control circuit (52) coupled to the magnetic field signal generating circuit (20) and comprising the switch (38) and a single-pulse circuit (48), wherein the single-pulse circuit (48) responds to an edge of each pulse of the externally generated trigger signal (54; 62) to generate a single-pulse output pulse (46), and the switch (38) responds to the single-pulse output pulse (46) to trigger the generation of a supply current pulse (80), wherein the supply current pulse (80) activates the magnetic field signal generating circuit (20) for a predetermined time interval, wherein The predetermined time interval is determined by the control circuit. [20] Sensor according to claim 19, wherein the supply current pulse (80) has a duration determined by the single-pulse circuit (48) and the capacitor (51).

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