Magnetic field sensor circuit in a package with means for adding a signal from a coil

Abstract

Magnetic field sensor system (10) comprising the following: a sensor package (14); a first magnetic sensor (32) arranged within the sensor package (14), wherein the first magnetic sensor (32) is configured to measure a first magnetic field in a first frequency range and to output a first sensor signal based on the measured first magnetic field; a second magnetic sensor (12) arranged outside the sensor package (14) and electrically coupled to the sensor package (14), wherein the second magnetic sensor (12) is configured to measure a second magnetic field in a second frequency range encompassing frequencies higher than those of the first frequency range, and to output a second sensor signal based on the measured second magnetic field, wherein the first magnetic sensor (32) and the second magnetic sensor (12) share an overlap frequency; and a sensor circuit (34) arranged within the sensor package (14) and electrically coupled to the first magnetic sensor (32) and the second magnetic sensor (12), wherein the sensor circuit (34) is configured to receive the first sensor signal and the second sensor signal and to output a combined sensor signal derived from the first sensor signal and the second sensor signal.

Description

Field of invention

[0001] The present disclosure relates generally to devices and methods for sensing a magnetic field, and more particularly to magnetic field sensors. background

[0002] Sensors generally measure a physical quantity and convert the measured physical quantity into a signal that is provided to an electronic device (e.g., a processor on an integrated circuit). Magnetic sensors, for example, measure a magnetic field using one or more magnetic field sensing elements that are sensitive to magnetic fields and output an electrical signal (e.g., a voltage signal or a current signal) corresponding to the measured magnetic field.

[0003] A sensor package may also include a signal processing circuit that receives the signal (i.e., the sensor signal) from the magnetic field sensor element and derives a measurement signal from the sensor signal. Therefore, a sensor package may include a magnetic field sensor and a circuit that processes and amplifies the small signal from the magnetic field sensor via signal conditioning.

[0004] Magnetic field sensor elements typically have either limited magnetic sensitivity or limited bandwidth. For example, a Hall plate has a moderate magnetic sensitivity of 50 mV / V / T, and its bandwidth is limited to 30 kHz due to eddy currents in the leadframe of a leaded package, or to a bandwidth of 150 kHz due to the signal conditioning circuitry within the package. The signal conditioning circuitry can be, for example, a spin Hall probe circuit, which is a discrete-time circuit operating at a chopper frequency of 50–500 kHz.

[0005] Additionally, the aforementioned magnetic field sensor elements are resistive devices with a typical resistance of a few kiloohms, which generates a high level of noise at high frequencies (e.g., in the MHz range). This further limits the frequency at which these sensor elements can operate.

[0006] An on-chip coil arranged on a surface of a semiconductor chip can also be used as a magnetic field sensing element. The on-chip coil can exhibit a wide bandwidth if it is not mounted near a conductive plate, such as the lead frame. However, the on-chip coil has limited magnetic sensitivity because its effective area is small (e.g., on the order of a few square millimeters) due to the small size of the semiconductor die. The number of turns is also limited to 10–1000 due to the limited metallization layers available in commercial microelectronic processes.

[0007] Given the above, current magnetic field sensors have a limited signal-to-noise ratio (SNR) at large bandwidths.

[0008] DE 100 62 292 A1 describes a measuring system, particularly for detecting magnetic fields, comprising a parallel connection of a low-frequency measuring system and a high-frequency measuring system, each of which has a sensor for detecting a signal to be measured. The low-frequency signal components provided by the low-frequency measuring system and the high-frequency signal components of the signal to be measured provided by the high-frequency measuring system are combined in a logic element. On the output side, the measuring system provides an output signal that represents a highly precise image of the signal to be detected over a wide frequency range.

[0009] DE 10 2008 061 067 B4 describes an integrated circuit having the following features: a chip; a first magnetic field sensitive element formed on the chip and configured to detect a magnetic field in a first frequency range and output a first measurement signal; a first coil formed on the chip and around the first magnetic field sensitive element and configured to detect a magnetic field in a second frequency range having higher frequencies than the first frequency range and output a second measurement signal; a second magnetic field sensitive element formed on the chip and configured to output a third measurement signal; a second coil formed on the chip and around the second magnetic field sensitive element and configured to output a fourth measurement signal;a first amplifier configured to amplify a first signal indicative of a difference between the first measurement signal and the third measurement signal; and a second amplifier configured to amplify a second signal indicative of a difference between the second measurement signal and the fourth measurement signal; and means configured to combine a signal based on the first signal and a signal based on the second signal and output a signal indicative of a magnetic field acting on the first magnetic field-sensitive element, the second magnetic field-sensitive element, the first coil, and the second coil.

[0010] DE 10 2014 113 213 A1 describes a Hall effect sensor circuit comprising two circuit sections, a first with a higher bandwidth for higher frequencies and with improved signal-to-noise ratio, and a second with a lower bandwidth for lower frequencies and with a low residual offset. First and second Hall plates or devices are incorporated in the first and second circuit sections. The first Hall plate can be operated with a higher bias voltage and a higher, high-pass filtered signal width, while the second Hall plate can be operated with a lower bias voltage and a lower, low-pass filtered signal width. Individual output signals from the first and second Hall plates can be scaled and combined to provide an overall output signal.

[0011] EP 1 873 543 A1 describes a device for magnetic field compensation which has two sensors operating in different frequency ranges and thus enables control with a bandwidth of 0 to 20 kHz. Brief description

[0012] The embodiments provide a device or system comprising: a sensor package, a first magnetic sensor arranged within the sensor package, wherein the first magnetic sensor is configured to measure a first magnetic field in a first frequency range and output a first sensor signal based on the measured first magnetic field, a second magnetic sensor arranged outside the sensor package and electrically coupled to the sensor package, wherein the second magnetic sensor is configured to measure a second magnetic field in a second frequency range comprising higher frequencies than the frequencies of the first frequency range and output a second sensor signal based on the measured second magnetic field, wherein the first magnetic sensor and the second magnetic sensor share a crossover frequency, and a sensor circuit,which is arranged within the sensor package and is electrically coupled to the first magnetic sensor and the second magnetic sensor, wherein the sensor circuit is configured to receive the first sensor signal and the second sensor signal, combine the first sensor signal and the second sensor signal, and output a combined sensor signal derived from combining the first sensor signal with the second sensor signal.

[0013] The embodiments further provide a method for measuring magnetic fields using a first magnetic sensor arranged within a sensor package and a second magnetic sensor arranged outside the sensor package. The method includes: measuring a first magnetic field in a first frequency range by the first magnetic sensor; outputting a first sensor signal based on the measured first magnetic field by the first magnetic sensor; measuring a second magnetic field in a second frequency range comprising higher frequencies than the frequencies of the first frequency range by the second magnetic sensor, wherein the first magnetic sensor and the second magnetic sensor share a crossover frequency; outputting a second sensor signal based on the measured second magnetic field by the second magnetic sensor, by a sensor circuit arranged within the sensor package,to receive the first sensor signal and the second sensor signal, to combine the first sensor signal and the second sensor signal by the sensor circuit, and to output a combined sensor signal derived from the combination of the first sensor signal and the second sensor signal by the sensor circuit. Short description of the drawings

[0014] The embodiments are described herein with reference to the accompanying drawings. Fig. 1 shows a cross-sectional view of a magnetic field sensor system according to one or more embodiments; Fig. 2 shows a plan view of the magnetic field sensor system according to the Fig. 1; Fig. 3 shows a cross-sectional view of a magnetic field sensor system according to one or more further embodiments; Fig. 4 shows a cross-sectional view of a magnetic field sensor system according to one or more further embodiments; and Fig. 5 shows a flowchart of a method for measuring magnetic fields according to one or more further embodiments. Detailed description

[0015] Several details are set forth below to provide a more thorough explanation of the exemplary embodiments. However, it will be apparent to those skilled in the art that the embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form or in a schematic view rather than in detail to avoid obscuring embodiments. Additionally, features of the various embodiments described below may be combined with one another unless specifically stated otherwise.

[0016] Furthermore, equivalent or identical elements, or elements with equivalent or identical functionality, are denoted by equivalent or identical reference numerals in the following description. Because the same or functionally equivalent elements are given the same reference numerals in the figures, a repeated description for elements provided with the same reference numerals can be omitted. Thus, descriptions provided for elements with the same or similar reference numerals are mutually interchangeable.

[0017] It is understood that when an element is described as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intervening elements. Conversely, when an element is described as being "directly connected" or "directly coupled" to another element, there are no intervening elements. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0018] In the embodiments described here or shown in the drawings, any direct electrical connection or coupling, i.e. any connection or coupling without additional intermediary elements, may also be implemented by an indirect connection or coupling, i.e. a connection or coupling with one or more intermediary elements, or vice versa, as long as the general purpose of the connection or coupling, for example to transmit a certain type of signal or to transmit a certain type of information, is substantially retained. Features from different embodiments may be combined to form further embodiments. For example, variants or modifications described with respect to one of the embodiments may also be applicable to other embodiments, unless otherwise stated.

[0019] Signal conditioning, as used here, refers to the manipulation of an analog signal in such a way that the signal meets the requirements of a next stage for further processing. Signal conditioning may include analog-to-digital conversion (e.g., via an analog-to-digital converter), amplification, filtering, converting, biasing, ranging, separation, and any other processes required to make a sensor output suitable for post-conditioning processing.

[0020] The embodiments relate to sensors and sensor systems and to determining information about sensors and sensor systems. As already mentioned in the Background section, a sensor can refer to a component that converts a physical quantity to be measured into an electrical signal, for example, a current signal or a voltage signal. The physical quantity can include, for example, but is not limited to, a magnetic field, an electric field, a pressure, a force, a current, or a voltage. A sensor device as described here can be a current sensor, a magnetometer, an angle sensor, a linear position sensor, a speed sensor, and the like.

[0021] For example, a magnetic field sensor includes one or more magnetic field sensing elements that measure one or more characteristics of a magnetic field (e.g., a magnitude of magnetic field flux density, a field strength, a field angle, a field direction, a field orientation, etc.), which corresponds to detecting and / or measuring the magnetic field line image of an element that generates the magnetic field (e.g., a magnet, a current-carrying conductor (e.g., a wire), the ground, or another magnetic field source).

[0022] According to one or more embodiments, a magnetic field sensor and a sensor circuit are both housed in the same chip package (e.g., a plastic-encapsulated package, such as a leaded package or a leadless package, or a surface-mounted device (SMD) package). This chip package is also referred to as the sensor package. One or more magnetic field sensor elements, or a magnetic field sensor for short, contained in the sensor package is thus exposed to a magnetic field, and the sensor signal provided by the magnetic field sensor element (e.g., a voltage signal) is, for example, proportional to the magnitude of the magnetic field.

[0023] The sensor circuit can be referred to as a signal processing circuit and / or a signal conditioning circuit, which receives the signal (i.e., the sensor signal) from the magnetic field sensor element and derives a measurement signal representing the magnetic field from the sensor signal. Therefore, the sensor package includes a circuit that conditions and amplifies the small signal from the magnetic field sensor through signal processing and / or conditioning.

[0024] A sensor device, as used herein, may refer to a device that includes a sensor and a sensor circuit, as described above. A sensor device may be integrated on a single semiconductor die (e.g., a silicon die or chip), although in other implementations, multiple dies may be used to implement a sensor device. Thus, the sensor and the sensor circuit are arranged either on the same semiconductor die or on multiple dies in the same package. For example, the sensor could be on one die and the sensor circuit on a different die, such that they are electrically connected within the package. In this case, the dies may be made of the same or different semiconductor materials, such as GaAs and Si, or the sensor may be sputtered onto a non-semiconductor ceramic or glass die.

[0025] Magnetic field sensing elements include Hall plates, vertical Hall-effect devices, magnetoresistive sensors, often referred to as XMR sensors (a collective term for anisotropic magnetoresistive (AMR), giant magneto-resistive (GMR), tunneling magneto-resistive (TMR), and colossal magneto-resistive (CMR) sensors, or magnetic-field-sensitive metal-oxide-semiconductor field-effect transistors (MOSFETs) (MAGFETs). It is also possible to use on-chip coils, which are fabricated from an interconnect layer of the semiconductor process (e.g., the wiring layers) and arranged on the surface of the semiconductor chip(s).It is also possible to use GMI (Giant Magneto-Impedance) devices that are not built into / on the surface or volume of a die, but are wired onto some support structure, so that the magnetic field sensitive device does not necessarily have to be associated with a die or chip.

[0026] According to one or more embodiments, input terminals are provided on the sensor package to which an off-chip sensor element is connected. Thus, an on-chip magnetic sensor and an off-chip magnetic sensor are provided, providing a combined wide frequency bandwidth. For example, the sensors can be configured to detect a magnetic field over a frequency bandwidth from 0 Hz (i.e., direct current (DC)) up to the MHz range (e.g., one or more MHz).

[0027] The on-chip magnetic sensor may include any of the previously mentioned magnetic field sensor elements and may be referred to as a Hall sensor, an XMR sensor (e.g., AMR sensor, GMR sensor, TMR sensor, CMR sensor), a MAGFET, a coil sensor, a GMI sensor, or the like.

[0028] In one or more embodiments, the on-chip magnetic sensor may include one or more spinning-current Hall plates operating in a spinning-current mode. A spinning-current Hall plate may be configured with four terminals, in which current is sent to a first pair of terminals (e.g., supply terminals), while a second pair of terminals is used to sense an output voltage (e.g., sense terminals). Ideally, a Hall plate is perfectly symmetrical, so that in the presence of a zero applied magnetic field, there is a zero output voltage. In practice, however, some asymmetry is likely to exist, introducing an undesirable offset into the measurement. To compensate for this asymmetry, a spinning-current mode may be used.

[0029] In spinning-current mode, the spinning-current Hall plate operates in a spinning-current mode, using two operating phases so that the supply terminals and the sense terminals are repeatedly switched between the terminal pairs. The signals from the two operating phases are summed by a sensor circuit, thus canceling the offset errors caused by the asymmetry.

[0030] However, spinning-current mode is not a time-continuous procedure (i.e., it is a time-discrete procedure comprising multiple operating phases); it typically cannot be used at high frequencies because a higher offset error results and its compensation becomes more difficult. Thus, according to one or more embodiments, an on-chip magnetic sensor using spinning-current Hall plates may be configured to operate at frequencies of about 150 kHz or less, and may be further configured to operate at about 100 kHz or less, at about 10 kHz or less, or at about 1 kHz or less. The frequency at which a sensor can operate is directly proportional to the frequency of the magnetic field the sensor can detect.

[0031] The off-chip magnetic sensor may be one or more induction coils or may consist of one or more induction coils and may also be referred to as a coil system. A coil, according to this example, may be a wound metal comprising thin or thick wires with a small or large number of turns and of small or large size. This coil may be implemented with conductive traces in a printed circuit board (e.g., a printed circuit board (PCB)) to which the sensor package can be attached and electrically connected. This coil may contain additional means, such as flux concentrators, that concentrate the magnetic flux through the coil. These flux concentrators may comprise soft magnetic material, such as soft ferrites; this is particularly suitable for high operating frequencies in the MHz range.This coil can be round, rectangular, flat or on curved surfaces, cylindrical, single-layer or multi-layer.

[0032] The coil can be a simple or a differential coil. The simple coil can be a non-differential coil, with one terminal connected to signal ground and another terminal outputting a sensor signal to the sensor package.

[0033] A differential coil can be a coil divided into two parts or windings, each with the same product of area times the number of turns but a different sign of the induced voltage when subjected to time-varying, spatially homogeneous magnetic fields. For example, a coil consists of N turns distributed over an area A, such that the product of area times the number of turns is N*A. In a differential coil, there are two coils, each with an equal product of area times the number of turns, N1*A1 and N2*A2, respectively (i.e., N1*A1 = N2*A2). However, for each coil of a differential coil, only the product needs to be the same; they do not need to have the same number of turns or the same area. Thus, N1 and N2 can be different, and A1 and A2 can also be different.Thus, the differential coil has two output terminals, one for each coil, winding (or subwinding).

[0034] The purpose of differential coils is to cancel homogeneous magnetic interference while still responding to magnetic field gradients of the field to be detected. For example, the differential coil can detect a voltage (i.e., the sensor signal of the off-chip magnetic sensor) across two terminals of the differential coil. The voltage is equal to d(N1*A1*B1) / dt - d(N2*A2*B2) / dt, where B1 and B2 are the external magnetic fields detected at coil 1 and coil 2, respectively, N1*A1*B1 is the total magnetic flux through coil 1, N1*A2*B2 is the total magnetic flux through coil 2, and the voltage is the difference between the two time derivatives.

[0035] In a simple case, there is only one signal input terminal, for example, a dedicated lead of the sensor package connected to the off-chip coil (e.g., in the case of a simple coil). The signal input terminal of the sensor package is connected to the semiconductor die within the sensor package.

[0036] In another example, the off-chip coil may have two output terminals (e.g., in the case of a differential coil). For an off-chip coil that has two output terminals, each output terminal is connected to the sensor package. Thus, the sensor package may be provided with two or more dedicated signal input terminals to which the coil can be connected to receive sensor signals. For more complex coil systems, a larger number of signal input terminals (e.g., two or more) may be provided on the sensor package.

[0037] The signal ground may be provided externally to the sensor package or may additionally or alternatively be achieved by a connection to a terminal (e.g., a dedicated wire) of the sensor package that is connected to the signal ground.

[0038] The sensor package's signal input terminals can be routed through an electronic circuit (e.g., a sensor circuit) within the sensor package that processes the coil(s) signal(s) (e.g., through amplification and low-pass / high-pass / band-pass / band-stop filtering or integration). Finally, this sensor circuit combines the coil signal(s) with the signal(s) from the on-chip magnetic field sensor element(s).

[0039] According to the above, a magnetic field sensor system is provided that includes two sensor elements: an on-chip magnetic sensor and an off-chip magnetic sensor. The on-chip magnetic field sensor (i.e., the on-chip low-frequency sensor) detects static and low-frequency magnetic fields, while the off-chip magnetic sensor (i.e., the off-chip high-frequency sensor) detects high-frequency magnetic fields. The signals from the on-chip and off-chip sensor elements are combined to yield a response that is flat from zero (e.g., direct current (DC)) to a few MHz. The off-chip magnetic sensor may be an off-chip coil, as described herein.

[0040] Additionally, increased design flexibility can be achieved by providing the coil off-chip because the coil is not bound by the same design considerations as on-chip coils. For example, if the off-chip coil is separated from the on-chip sensor, the off-chip coils can be configured to achieve high sensitivities (e.g., through many turns of the winding), so that the crossover frequency between the on-chip and off-chip sensor elements in the signal conditioning and combining circuitry can be selected at very low frequencies. Thus, frequencies detected by the on-chip sensor that are above the crossover frequency are attenuated in the on-chip sensor signal path, and frequencies detected by the off-chip sensor that are below the crossover frequency are attenuated in the off-chip sensor signal path.

[0041] For example, if a coil is on-chip, it is difficult to use the coil for frequencies below 20 kHz due to the size limitations of the chip (i.e., a larger coil with a larger number of turns is required). Therefore, for example, an on-chip Hall plate sensor would have to cover a range from 0 Hz to 20 kHz, which is difficult to achieve. However, if an off-chip coil is used according to the embodiments disclosed here, the coil can consist of many turns with a larger area and can be used down to frequencies of about 1 kHz. Thus, an on-chip Hall plate sensor only needs to cover 0 Hz to about 1 kHz, which is much more feasible. In this lower frequency range (i.e., lower bandwidth), the sensor circuit (e.g.,The Hall plate sensor conditioning circuit (such as a spinning current circuit) can be optimized to produce less residual offset and less noise than with a wider bandwidth of 0 Hz to 20 kHz.

[0042] If the on-chip magnetic sensor is a spinning current Hall device with one or more spinning current Hall plates, the crossover frequency may be about 150 kHz or less, and more preferably about 100 kHz or less, and more preferably about 10 kHz or less, and more preferably about 1 kHz or less, wherein the off-chip sensor may operate at a frequency from the crossover frequency up to 1 MHz or more.

[0043] Furthermore, higher frequencies can create a problem for a sensor circuit due to the leadframe of a typical plastic-encapsulated package. In particular, the high-frequency components of the magnetic field to be measured can cause large eddy currents in the leadframe, distorting the frequency response of the sensor circuit. However, according to the embodiments disclosed herein, this problem can be avoided by using only a low-frequency sensor (e.g., a Hall plate sensor) in the sensor package, where eddy currents are a problem. Instead, the high-frequency component of the signal is provided by the off-chip coil, which is not limited by the leadframe of the sensor package.

[0044] The magnetic field sensor system as provided herein can be used as a current sensor, but is not limited to this. For example, the magnetic field sensor system can be used as a current sensor if it is coupled with the magnetic field generated by any current to be measured flowing through a primary conductor. For example, contactless current measurement can be achieved by using the magnetic field sensor system to detect the magnetic field caused by a current flowing through the primary conductor (hereinafter referred to as the primary current). The magnetic field caused by the primary current depends on the magnitude of the primary current. For a long, straight wire carrying a primary current i p For example, the magnitude of the resulting magnetic field H at a distance d from the wire is directly proportional to the primary current i pAccording to the Biot-Savart law, the magnitude of the magnetic field H is H = i p / (2πd) if the wire is very long compared to the distance d (theoretically infinitely long).

[0045] According to one or more embodiments, a sensor package containing the magnetic field sensor element (e.g., a Hall sensor) is placed close to the primary conductor. The magnetic field sensor element (or magnetic field sensor) contained in the sensor package is thus exposed to the magnetic field caused by the primary current, and the sensor signal provided by the magnetic field sensor element (usually a voltage signal) is proportional to the magnitude of the magnetic field and thus also proportional to the primary current. Thus, the on-chip magnetic sensor is provided to cover a lower frequency range of the magnetic field generated by the primary current.

[0046] Similarly, the off-chip coil is placed close to the primary conductor to measure a higher frequency range of the magnetic field generated by the primary current.

[0047] The Fig. 1 shows a cross-sectional view of a magnetic field sensor system 10 according to one or more embodiments. The magnetic field sensor system 10 includes an off-chip magnetic sensor 12 (e.g., the off-chip coil 12) and a sensor package 14, each arranged on a circuit board 16. It should be understood that the circuit board 16 is not limited thereto and may be any printed circuit board (e.g., an insulated metal plane) and may consist of a single or multiple layers. This structure may collectively be referred to as a substrate.

[0048] The off-chip coil 12 may be a dedicated device on a plastic coil winding form (not shown), or it may be implemented as a printed circuit board trace so that it is integrated into the circuit board. For example, in a multi-layer circuit board, the off-chip coil 12 may be formed in an upper layer, a lower layer, or an intermediate layer of the circuit board 16.

[0049] The sensor package 14 may include a non-magnetic package or housing made of cast resin with a copper leadframe. Furthermore, the leads of the sensor package 14 and the off-chip coil 12 may be integrated into the circuit board and may be located below the sensor package 14.

[0050] The magnetic field sensor system 10 further includes conductive traces 18. For example, one or more conductive traces 18 may be an interconnect for connecting one or more terminals of the off-chip coil 12 to one or more terminals or traces of the sensor package 14. Furthermore, one or more conductive traces 18 may be connected to one or more terminals of the sensor package 14 to provide a connection to the sensor supply and sensor ground, and to provide a connection to output signals (e.g., measurement signals) from the sensor package 14.

[0051] The sensor package 14 includes a housing 20, a semiconductor die 22 arranged on a die paddle 24, and a leadframe consisting of terminals 28 (e.g., leads) for receiving or transmitting signals and / or supplying power. For example, terminal 28a is connected to the off-chip coil 12 and configured to receive a coil input (e.g., the measurement signal). Terminal 28b is connected to a conductive trace 18 and to one or more components of the sensor package 14.

[0052] The die paddle 24 is a thin metal surface within a packaged integrated circuit to which a die 22 is attached and which in turn is part of the system carrier (e.g., the terminals 28).

[0053] The semiconductor die 22 includes an on-chip magnetic sensor 32 and a sensor circuit 34, each arranged on and integrated within a semiconductor die 22.

[0054] The on-chip magnetic sensor 32 may be disposed on or near a top surface of the semiconductor die 22. The on-chip magnetic sensor 32 may be a spinning current Hall device or another magnetic sensor capable of detecting static and low-frequency magnetic fields.

[0055] The sensor circuit 34 may be a signal conditioning and combining circuit, as described above, and may further include a spinning current Hall probe circuit. In particular, the sensor circuit 34 receives raw measurement signals (e.g., analog signals) from the off-chip coil 12 and the on-chip magnetic sensor 32, processes the raw measurement signals, and combines the processed signal(s) from the off-chip coil 12 with the processed signal(s) from the on-chip magnetic sensor 32. The combined signal may then be output from the sensor package 14 through one of the terminals 28 to one of the conductive traces 18, which provides the combined signal to an external device (e.g., an external processor). Furthermore, it should be understood that specific circuit structures are not shown because the sensor circuit 34 is integrated on the semiconductor die 22.

[0056] Because the off-chip coil 12, as a passive component, is normally not supplied with electrical power, its DC potential is undefined. As a result, the sensor circuit 34 can be configured to define the common-mode potential of at least one of the at least two input terminals for the coil 12.

[0057] The magnetic field sensor system 10 may be configured such that a primary conductor 40 is provided on or near an opposite side of the circuit board 16 from the side on which the off-chip coil 12 and the sensor package 14 are provided. A primary current flowing through the primary conductor 40 generates a magnetic field 42, which is sensed by the off-chip coil 12 and the on-chip magnetic sensor 32. The off-chip coil 12 is provided to cover a higher frequency range of the magnetic field generated by the primary current, while the on-chip magnetic sensor 32 is provided to cover a lower frequency range of the magnetic field generated by the primary current.

[0058] Furthermore, although certain embodiments describe the use of the magnetic field sensor system 10 as a current sensor, it should be understood that the magnetic field sensor system 10 is not so limited and can be used to detect any magnetic field generated in various ways where measuring lower and higher frequency components or ranges is desired. For example, the field sensor system 10 can be used as a speed sensor for a magnetic field produced by a permanent magnet rotating on a gear pulley of a transmission or a gear.

[0059] As in the Fig. As shown in Figure 1, the circuit board 16 defines the gap between the sensing elements and the primary conductor 40, allowing a desired magnetic sensitivity for the sensing elements to be configured. Furthermore, the circuit board serves as a galvanic isolator with a large creepage distance between the primary conductor 40 and the sensor circuit 34.

[0060] As further described below, the off-chip coil 12 and the on-chip magnetic sensor 32 may be configured as differential sensors, with an equal number of subcomponents of each sensor arranged symmetrically about a central (longitudinal) axis of the primary conductor 40. A longitudinal axis is, for example, an axis that runs lengthwise through an object. Although certain embodiments are described herein as having symmetrically arranged components, it should be understood that the components may be arranged asymmetrically.

[0061] The Fig. 2 shows a plan view of the magnetic field sensor system 10 according to the Fig. 1, except that circuit board 16 has been removed for illustrative purposes only. In particular, the Fig. 2, the off-chip coil 12 and the on-chip magnetic sensor 32 are configured as differential sensors in which an equal number of subcomponents of each sensor are arranged to detect a magnetic field produced by a primary conductor 40.

[0062] For example, in the Fig. 2, the off-chip coil 12 is a differential coil including a first coil 12a and a second coil 12b, which may be arranged symmetrically about a central (longitudinal) axis 41 of the primary conductor 40 such that right-of-center and left-of-center symmetry is achieved. That is, a portion of the coil 12a and a corresponding counterpart of the coil 12 may be located laterally (e.g., in the y-direction) and vertically (e.g., in the z-direction) at approximately the same distance (taking into account standard manufacturing tolerances of 5%) from a central axis 41 of the primary conductor 40. The first coil 12a and the second coil 12b are connected to each other in a subtractive manner to cancel homogeneous background fields. These coils 12a and 12b may be dedicated devices on plastic coil winding forms (not shown), or they may be implemented as circuit board traces so that they are integrated into the circuit board 16.

[0063] The differential coil can detect a voltage (i.e., the sensor signal of the off-chip magnetic sensor) across two terminals 18 of the differential coil. The voltage is equal to d(N1*A1*B1) / dt - d(N2*A2*B2) / dt, where B1 and B2 are the external magnetic fields detected at coil 12a and coil 12b, respectively, N1*A1*B1 is the total magnetic flux through coil 12a, N1*A2*B2 is the total magnetic flux through coil 12b, and the voltage is the difference between the two time derivatives.

[0064] It is further understood that the first coil 12a and a second coil 12b may be arranged asymmetrically around the primary conductor.

[0065] The turn / area product N1*A1 of the first coil 12a is substantially equal (taking into account standard manufacturing tolerances of 5% or less) to the turn / area product N2*A2 of the second coil 12b.

[0066] Similarly, the on-chip magnetic sensor 32 may include two or more sets of magnetic sensor elements 32a and 32b arranged symmetrically (or asymmetrically) about a central (longitudinal) axis 41 of the primary conductor 40 (taking into account standard manufacturing tolerances of 5%). As shown in the Fig. 2, the sets of magnetic sensor elements 32a and 32b each include two Hall plates for measuring the magnetic field 42. Thus, in this example, four magnetic sensor elements are present. However, it should be understood that only one set of magnetic sensor elements may be used, and that a set may include one or more magnetic sensor elements. It should also be understood that the magnetic sensor elements are not limited to Hall plates and may be any type of magnetic sensor element (e.g., the magnetic sensor elements described above).

[0067] The magnetic sensor elements of sets 32a and 32b are connected to the sensor circuit 34 in a subtractive manner to cancel homogeneous magnetic background interference.

[0068] It is further understood that, although the symmetry of the off-chip coils and the on-chip magnetic sensor elements may help cancel homogeneous magnetic background noise and / or maximize sensitivity to the primary current in one or more embodiments, the off-chip coils and the on-chip magnetic sensor elements may not be symmetric about the central axis in other implementations.

[0069] The terminals of coils 12a and 12b can be connected to one of the conductor tracks 18, each of which interconnects the terminals 28, to provide a coil input. The other six terminals 28 of the sensor package 14 can be connected to the conductor tracks 18 for sensor power, a sensor ground, and one or more output signals.

[0070] The circuit board 16 can further serve as a galvanic isolation with a large creepage distance (e.g. in the x and y directions) between the primary conductor 40 and the sensor circuit 34.

[0071] As stated above, because the off-chip coil 12, as a passive component, is not normally supplied with electrical power, its DC potential is undefined. As a result, the sensor circuit 34 can be configured to define the common-mode potential of at least one of the at least two input terminals for the coil.

[0072] The Fig. 3 shows a cross-sectional view of a magnetic field sensor system 10 according to one or more further embodiments. In particular, the magnetic field sensor system 10 includes an off-chip coil 12 on a dedicated coil winding form 13 with a ferrite core. Furthermore, the off-chip coil 12 is connected to the sensor package 14 via a conductive trace 18. The coil winding form 13 can be placed on the substrate 19, which can be another circuit board trace, a pad, or a separate substrate (e.g., made of plastic) to keep the off-chip coil 12 planar to the primary conductor 40. As described above, it is understood that the conductive traces 18 and 19 can be integrated into the circuit board 16, such that the dedicated coil winding form 13 is placed directly on the circuit board 16.

[0073] It is understood that other elements of the Fig. 3 are similar to those previously described. Thus, their description is omitted for the sake of brevity.

[0074] The Fig. 4 shows a cross-sectional view of a magnetic field sensor system 10 according to one or more further embodiments. In addition to the magnetic field 42, the primary conductor 40 can produce an electric field 43. The primary conductor 40 can, for example, be at a high potential and can be subject to steep voltage jumps, which can couple into the sensor circuit 34 within the sensor package 14 via the off-chip coil 12.

[0075] Accordingly, an electrical shield 15 may be provided in the circuit board 16 to shield the off-chip magnetic sensor 12 from the electric field 43. The electrical shield 15 may be implemented with a multilayer circuit board 16 such that it is formed in an intermediate layer (e.g., between the top and bottom surfaces of the circuit board 16). The electrical shield 15 is also connected to ground via a via 17. For example, the via 17 may extend from one surface of the circuit board 16 into the circuit board 16 to the electrical shield 15. At the surface of the circuit board 16, the via 17 may be connected to a conductive trace 18 connected to the sensor ground. Alternatively, the connection to the sensor ground may also be achieved by a wire bond (not shown) or the like.

[0076] The electrical shield 15 should not be solid because then the magnetic induction from the high-frequency components of the primary current in the primary conductor 40 can induce eddy currents in the shield 15, and this would distort the magnetic field 42 sensed by the off-chip magnetic sensor 12 and the on-chip magnetic field sensor 32. Thus, the electrical shield 15 can be a metal layer shield and should be configured to prevent eddy currents. For example, the electrical shield 15 can be implemented as a grid of fine wires, a mesh, or a spiral. Each of these shapes has notches in the layer to avoid large loops for eddy currents, but they still function well enough to shield the sensors 12 and 32 and the sensor circuit 34 from electric fields.

[0077] As stated above, because the off-chip coil 12, as a passive component, is not normally supplied with electrical power, its DC potential is undefined. As a result, the sensor circuit 34 can be configured to define the common-mode potential of at least one of the at least two input terminals for the coil.

[0078] It is understood that other elements of the Fig. 4 are similar to those previously described. Thus, their description is omitted for the sake of brevity.

[0079] Given the above, the on-chip magnetic sensor 32 can detect static and low-frequency magnetic fields, while the off-chip magnetic sensor 12 can detect high-frequency magnetic fields. The signals from the on-chip and off-chip sensor elements are then combined to produce a response that is flat from DC to a few MHz.

[0080] In addition, by separating the off-chip magnetic sensor 12 (e.g., the off-chip coil 12) from the sensor package 14, greater sensitivities for the off-chip magnetic sensor 12 can be achieved (e.g., by many turns of the winding or by a larger area of ​​the turns), so that the crossover frequency between the on-chip and off-chip sensor elements in the signal conditioning and combining circuit can be selected at very low frequencies.

[0081] The Fig. 5 shows a flowchart of a method 500 for measuring magnetic fields using a first magnetic sensor disposed within a sensor package and a second magnetic sensor disposed externally of the sensor package, wherein the first magnetic sensor and the second magnetic sensor share a crossover frequency. Although the flowchart shows a series of sequential operations, no specific order of performance, serial rather than simultaneous or overlapping performance of operations or portions thereof, or performance of the operations shown exclusively without the presence of intervening or intermediate operations should be inferred from this sequence unless explicitly stated. The process shown in this example is implemented, for example, by one or more of the magnetic field sensor systems described above.

[0082] According to the Fig.5, the method 500 includes the following: measuring a first magnetic field in a first frequency range by the first magnetic sensor (operation 501), measuring a second magnetic field in a second frequency range that is higher than the first frequency range by the second magnetic sensor (operation 502), outputting a first sensor signal based on the measured first magnetic field by the first magnetic sensor (operation 503), outputting a second sensor signal based on the measured second magnetic field by the second magnetic sensor (operation 504), receiving the first sensor signal and the second sensor signal by a sensor circuit arranged within the sensor package (operations 505a and 505b), combining the first sensor signal and the second sensor signal by the sensor circuit (operation 506), and outputting a combined sensor signal by the sensor circuit,which has been derived by combining the first sensor signal and the second sensor signal (operation 507).

[0083] A single magnetic field source can generate the first magnetic field and the second magnetic field.

[0084] The crossover frequency may be a frequency greater than 0 Hz and less than 20 kHz. Furthermore, the first frequency range may include a frequency of 0 Hz, and the second frequency range may include a frequency of at least 1 MHz.

[0085] While various embodiments have been described herein, it will be apparent to those skilled in the art that many other embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not limited except as defined by the appended claims and their equivalents. With respect to the various functions performed by the above-described components and structures (assemblies, devices, circuits, systems, etc.), unless otherwise indicated, it is intended that the terms (including a reference to a "means") used to describe such components correspond to any component or structure that performs the specified function of the described component (i.e.which is functionally equivalent), even if it is not structurally equivalent to the disclosed structure that performs the function in the embodiments of the invention illustrated herein.

[0086] Furthermore, the following claims are hereby incorporated into the Detailed Description, each claim standing on its own as a separate exemplary embodiment. While each claim may stand on its own as a separate exemplary embodiment, it should be noted that although a dependent claim may refer to a specific combination with one or more other claims in the claims, other exemplary embodiments may also include a combination of the dependent claim with the subject matter of any other dependent or independent claim. Such combinations are suggested herein unless it is stated that a specific combination is not intended. Furthermore, it is intended to include features of a claim in any other independent claim, even if that claim is not directly made dependent on the independent claim.

[0087] It should further be noted that methods disclosed in the patent description or in the claims may be implemented by an apparatus having means for performing each of the corresponding operations of those methods.

[0088] Furthermore, it should be understood that the disclosure of multiple acts or functions disclosed in the specification or claims should not be construed as being in any specific order. Accordingly, the disclosure of multiple acts or functions will not limit them to any particular order unless such acts or functions are not interchangeable for technical reasons. Furthermore, in some embodiments, a single act may have, or may be broken down into, multiple sub-acts. Such sub-acts may be included and are part of the disclosure of that single act unless expressly excluded.

Claims

[1] Magnetic field sensor system (10) comprising: a sensor package (14); a first magnetic sensor (32) arranged within the sensor package (14), wherein the first magnetic sensor (32) is configured to measure a first magnetic field in a first frequency range and to output a first sensor signal based on the measured first magnetic field; a second magnetic sensor (12) arranged outside the sensor package (14) and electrically coupled to the sensor package (14), wherein the second magnetic sensor (12) is configured to measure a second magnetic field in a second frequency range that includes higher frequencies than the frequencies of the first frequency range, and to output a second sensor signal based on the measured second magnetic field, wherein the first magnetic sensor (32) and the second magnetic sensor (12) share a crossover frequency; and a sensor circuit (34) disposed within the sensor package (14) and electrically coupled to the first magnetic sensor (32) and the second magnetic sensor (12), wherein the sensor circuit (34) is configured to receive the first sensor signal and the second sensor signal and to output a combined sensor signal derived from the first sensor signal and the second sensor signal. [2] The magnetic field sensor system (10) of claim 1, wherein the first magnetic field and the second magnetic field are generated by a same magnetic field source. [3] The magnetic field sensor system (10) of claim 2, wherein the magnetic field source is a conductor and the first and second magnetic fields are generated by a current flowing through the conductor. [4] Magnetic field sensor system (10) according to one of claims 1 to 3, wherein the sensor package (14) contains a semiconductor die (22) and the first magnetic sensor (32) and the sensor circuit (34) are integrated on the semiconductor die (22). [5] The magnetic field sensor system (10) of any one of claims 1 to 3, wherein the sensor package (14) includes a first semiconductor die having the first magnetic sensor (32) integrated thereon and a second semiconductor die having the sensor circuit (34) integrated thereon. [6] Magnetic field sensor system (10) according to one of claims 1 to 5, wherein the second magnetic sensor (12) is an induction coil including at least one terminal connected to the sensor package (14) to transmit the second sensor signal to the sensor circuit (34). [7] The magnetic field sensor system (10) of claim 6, wherein the induction coil is a differential induction coil having a first winding and a second winding arranged in a subtracting configuration, the first winding being configured to generate a first component of the second sensor signal and including a first terminal electrically coupled to the sensor package (14), and the second winding being configured to generate a second component of the second sensor signal and including a second terminal electrically coupled to the sensor package (14). [8] Magnetic field sensor system (10) according to claim 7, wherein the first winding and the second winding are arranged symmetrically about a central longitudinal axis (41) of a magnetic field source that generates the second magnetic field. [9] The magnetic field sensor system (10) of claim 7 or 8, wherein the sensor circuit (34) is configured to receive the first and second components of the second sensor signal and to derive the second sensor signal from the first and second components of the second sensor signal. [10] Magnetic field sensor system (10) according to one of claims 1 to 9, wherein the first magnetic sensor (32) includes a first set of sensor elements (32a) and a second set of sensor elements (32b), the first set of sensor elements (32a) being configured to generate a first component of the first sensor signal and the second set of sensor elements (32b) being configured to generate a second component of the first sensor signal. [11] The magnetic field sensor system (10) of claim 10, wherein the first set of sensor elements (32a) and the second set of sensor elements (32b) are electrically connected to the sensor circuit (34) in a subtracting configuration. [12] Magnetic field sensor system (10) according to claim 10 or 11, wherein the first set of sensor elements (32a) and the second set of sensor elements (32b) are arranged symmetrically about a central longitudinal axis (41) of a magnetic field source that generates the first magnetic field. [13] The magnetic field sensor system (10) of any one of claims 10 to 12, wherein each sensor element of the first and second set of sensor elements (32a, 32b) is a spinning current Hall plate configured to operate in a spinning current mode. [14] Magnetic field sensor system (10) according to one of claims 1 to 13, wherein the first magnetic sensor (32) is a Hall sensor. [15] Magnetic field sensor system (10) according to one of claims 1 to 14, wherein the crossover frequency is approximately 10 kHz. [16] Magnetic field sensor system (10) according to one of claims 1 to 15, wherein the crossover frequency is approximately 1 kHz. [17] Magnetic field sensor system (10) according to one of claims 1 to 16, wherein the crossover frequency is a frequency greater than 0 Hz and less than 10 kHz. [18] Magnetic field sensor system (10) according to one of claims 1 to 17, wherein the first frequency range includes a frequency of 0 Hz and the second frequency range includes a frequency of at least 1 MHz. [19] Magnetic field sensor system (10) according to one of claims 1 to 18, further comprising: a substrate on which the sensor package (14) and the second magnetic sensor (12) are arranged; and an electrical shield disposed in the substrate between the second magnetic sensor (12) and a magnetic field source to shield the second magnetic sensor (12) from an electric field generated by the magnetic field source. [20] Magnetic field sensor system (10) according to one of claims 1 to 19, wherein frequencies detected by the first magnetic sensor (32) which are above the crossover frequency are attenuated in a first signal path of the first magnetic sensor (32) and frequencies detected by the second magnetic sensor (12) which are below the crossover frequency are attenuated in a second signal path of the second magnetic sensor (12). [21] The magnetic field sensor system (10) of any one of claims 1 to 20, wherein the sensor circuit (34) is configured to combine the first sensor signal and the second sensor signal and output the combined sensor signal derived from combining the first sensor signal and the second sensor signal. [22] A method (500) for measuring magnetic fields, using a first magnetic sensor (32) arranged inside a sensor package (14) and a second magnetic sensor (12) arranged outside the sensor package (14), the method comprising: to measure (501) a first magnetic field in a first frequency range by the first magnetic sensor (32); outputting a first sensor signal based on the measured first magnetic field (503) by the first magnetic sensor (32); to measure a second magnetic field in a second frequency range comprising higher frequencies than the frequencies of the first frequency range by the second magnetic sensor (12), wherein the first magnetic sensor (32) and the second magnetic sensor (12) share a crossover frequency (502); outputting a second sensor signal based on the measured second magnetic field (504) by the second magnetic sensor (12); by a sensor circuit (34) arranged within the sensor package (14) to receive (505a, 505b) the first sensor signal and the second sensor signal; and to output by the sensor circuit (34) a combined sensor signal derived from the first sensor signal and the second sensor signal (507). [23] The method (500) of claim 22, further comprising: to generate the first magnetic field and the second magnetic field using a magnetic field source. [24] The method (500) of claim 22 or 23, wherein the crossover frequency is a frequency greater than 0 Hz and less than 20 kHz. [25] The method (500) of claim 24, wherein the first frequency range includes a frequency of 0 Hz and the second frequency range includes a frequency of at least 1 MHz. [26] The method (500) of any one of claims 22 to 25, further comprising: combining (506) the first sensor signal and the second sensor signal by the sensor circuit (34); and outputting, by the sensor circuit (34), the combined sensor signal derived from combining the first sensor signal and the second sensor signal (507).

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