MAGNETIC FIELD SENSOR CIRCUIT AND MAGNETIC FIELD MEASURING METHOD

Abstract

The present disclosure relates to a magnetic field sensor circuit (300) comprising a first bridge circuit (122-1) comprising a first series connection of a first magnetoresistive resistor (R1) and a second magnetoresistive resistor (R2), and a second bridge circuit (122-2) comprising a second series connection of a third magnetoresistive resistor (R7) and a fourth magnetoresistive resistor (R8). A first terminal between the first magnetoresistive resistor (R1) and the second magnetoresistive resistor (R2) of the first bridge circuit (122-1) is coupled to a second terminal between the third magnetoresistive resistor (R7) and the fourth magnetoresistive resistor (R8) of the second bridge circuit (122-2). The coupled first and second terminals provide a first output signal of the magnetic field sensor circuit (300).

Description

Area

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

[0002] In current sensing with internal and external busbars (or bus bars), it is common to attempt to place sensing elements in such an arrangement that a first sensing element is placed above the busbar and a second sensing element is placed adjacent to the first sensing element. This allows the current sensor to differentially sense the electrical current in the busbar. With the differential sensing architecture, the current sensor can be very robust to any homogeneous stray field present in the current sensing application. However, there may be sensing arrangements where it is preferable to be sensitive to homogeneous fields (e.g., in core-based current sensing or for linear torque sensing).

[0003] Another application is magnetic velocity sensing, where differential and / or monomode sensing is used to detect the speed and direction of rotation of a toothed ferrite wheel or a wheel with magnetic domains. As an example, dynamic switching between a monomode and differential mode reading was implemented in a giant magnetoresistance (GMR) device by measuring the resistance drop across a portion of a Wheatstone bridge in a monomode. In addition to the disadvantage that no Wheatstone bridge readout could be used for the monomode, the approach is even unfeasible for tunnel magnetoresistance (TMR) devices, since the field sensitivity is proportional to the conductivity, not the resistance, in the GMR. Additionally, it is difficult to adjust the gain when the sensitivities in the two modes do not match.

[0004] Typically, the sensing concept must be selected in advance and defined at the beginning of a sensor design. Once the architecture is selected, the overall design attempts to optimize either the differential signal capabilities or the homogeneous sensing capabilities. Additionally, it is not easy to create a flexible concept and make this selection through a simple configuration bit or metal mask configuration without significant circuit complexity.

[0005] The current state of the art is to select a sensing principle at the outset and then optimize the architecture to perfectly fit the application. This approach is very inflexible when it turns out that some applications may have different needs. This is even more of a problem if the application requires both modes simultaneously. This would require two sensors in different configurations, making the solution impossible to scale and adding costs.

[0006] Thus, there is a need to provide more flexible approaches to power sensing. Summary

[0007] This need is met by magnetic field sensor circuits and magnetic field detection methods according to the appended claims.

[0008] According to a first aspect, the present disclosure proposes a magnetic field sensor circuit. The magnetic field sensor circuit comprises a first bridge circuit comprising a first series circuit of a first magnetoresistance and a second magnetoresistance. The magnetic field sensor circuit further comprises a (separate) second bridge circuit comprising a second series circuit of a third magnetoresistance and a fourth magnetoresistance. A first terminal between the first and second magnetoresistances of the first bridge circuit is coupled to a second terminal between the third and fourth magnetoresistances of the second bridge circuit. The coupled first and second terminals provide a first output signal of the magnetic field sensor circuit. The first and second terminals may be short-circuited.In this way, a magnetic field or current sensor with at least one asymmetric output signal can be provided for both differential and homogeneous field detection.

[0009] The first and second bridge circuits may each be separate full or half Wheatstone bridges. The magnetic field sensor circuit may be implemented using discrete components or as one or more integrated circuits (ICs).

[0010] In some embodiments, the first magnetoresistance of the first bridge circuit includes a first reference magnetization. The second magnetoresistance of the first bridge circuit includes a second reference magnetization that is different from the first reference magnetization. The third magnetoresistance of the second bridge circuit includes the second reference magnetization (of the second magnetoresistance). The fourth magnetoresistance of the second bridge circuit includes the first reference magnetization (of the first magnetoresistance).

[0011] In some embodiments, the second reference magnetization is antiparallel to the first reference magnetization. Thus, the second reference magnetization is shifted by 180° relative to the first reference magnetization.

[0012] In some embodiments, the first series connection of the first bridge circuit is coupled between a first power supply terminal and a first ground terminal. The second series connection of the second bridge circuit is coupled between a second power supply terminal and a second ground terminal. While the first and second power supply terminals may refer to separate terminals, they may also refer to a common power supply terminal. Likewise, while the first and second ground terminals may refer to separate terminals, they may also refer to a common ground terminal.

[0013] In some embodiments, the first power supply terminal is coupled to a magnetoresistance of the first series circuit having the first reference magnetization, and the second power supply terminal is coupled to a magnetoresistance of the second series circuit having the second reference magnetization that differs from the first reference magnetization. Here, the power supply is connected to magnetoresistances of the first and second series circuits that have different reference magnetizations. Such a configuration can provide sensitivity of the magnetic field sensor circuit to differential field detection.

[0014] In some embodiments, the first power supply terminal is coupled to a magnetoresistance of the first series circuit (the first bridge circuit) having the first reference magnetization, and the second power supply terminal is coupled to a magnetoresistance of the second series circuit (the second bridge circuit) having the first reference magnetization. Here, the power supply is connected to magnetoresistances of the first and second series circuits that have the same reference magnetization. Such a configuration can provide sensitivity of the magnetic field sensor circuit for homogeneous field detection.

[0015] In some embodiments, the first series circuit (of the first bridge circuit) of the first magnetoresistance and the second magnetoresistance is coupled between a first power supply terminal and a first ground terminal, and the second series circuit (of the second bridge circuit) of the third magnetoresistance and the fourth magnetoresistance is coupled between a second ground terminal and a third ground terminal. Thus, while the first series circuit (of the first bridge circuit) may be coupled between a power supply and ground, the second series circuit (of the second bridge circuit) may be coupled between two ground terminals. Such a configuration may provide sensitivity of the magnetic field sensor circuit for both differential and homogeneous field sensing.

[0016] In some embodiments, the first series circuit (the first bridge circuit) of the first magnetoresistance and the second magnetoresistance is coupled between a power supply and ground. The magnetic field sensor circuit may further include a switch circuit configured to switch between different magnetic field sensing modes by modifying a power supply of the first second series circuit (the first bridge circuit) or the second series circuit (the second bridge circuit).

[0017] In some embodiments, the switch circuit is configured to couple the second series circuit of the third magnetoresistance and the fourth magnetoresistance between the power supply and ground in a first sensing mode, to switch the power supply and ground connections for the second series circuit compared to the first sensing mode in a second sensing mode, and / or to couple the second series circuit of the third magnetoresistance and the fourth magnetoresistance between two ground connections in a third sensing mode. In this way, the magnetic field sensor circuit can be configured for different sensing modes for differential and / or homogeneous field sensing.

[0018] In some embodiments, the first bridge circuit includes a third series circuit of a fifth magnetoresistance and a sixth magnetoresistance connected in parallel with the first series circuit. Thus, the first bridge circuit may be a full Wheatstone bridge circuit. The second bridge circuit includes a fourth series circuit of a seventh magnetoresistance and an eighth magnetoresistance connected in parallel with the second series circuit. Thus, the second bridge circuit may be a full Wheatstone bridge circuit. A third terminal between the fifth and sixth magnetoresistances of the first bridge circuit is coupled to a fourth terminal between the seventh and eighth magnetoresistances of the second bridge circuit. The coupled third and fourth terminals may provide a second output signal of the magnetic field sensor circuit. The third and fourth terminals may be short-circuited.In this way, a current sensor with a differential output signal can be provided.

[0019] In some embodiments, the fifth magnetoresistance of the first bridge circuit comprises the second reference magnetization (of the second magnetoresistance), the sixth magnetoresistance of the first bridge circuit comprises the first reference magnetization (of the first magnetoresistance), the seventh magnetoresistance of the second bridge circuit comprises the first reference magnetization, and the eighth magnetoresistance of the second bridge circuit comprises the second reference magnetization.

[0020] In some embodiments, the magnetic field sensor circuit further comprises a differential amplifier. A first input terminal of the differential amplifier is coupled to the first output signal, and a second input terminal of the differential amplifier is coupled to the second output signal of the magnetic field sensor. The differential amplifier can be implemented as an operational amplifier (op-amp) or an operational transconductance amplifier (OTA). The OTA is a specialized type of amplifier that provides an output current proportional to the difference between its input voltages. Unlike voltage amplifiers (operational amplifiers or op-amps), which provide an output voltage proportional to the input voltage difference, OTAs amplify the input voltage difference by converting it into an output current.

[0021] In some embodiments, the magnetoresistances of the first and second bridge circuits are giant magnetoresistances (GMR) or tunnel magnetoresistances (TMR).

[0022] According to another aspect, the present disclosure proposes a magnetic field measurement method. The method includes providing a first bridge circuit comprising a first series circuit of a first magnetoresistance and a second magnetoresistance, providing a second bridge circuit comprising a second series circuit of a third magnetoresistance and a fourth magnetoresistance, coupling a first terminal between the first and second magnetoresistances of the first bridge circuit to a second terminal between the third and fourth magnetoresistances of the second bridge circuit, and providing an output signal of the magnetic field sensor circuit to the coupled first and second terminals.

[0023] In some embodiments, the first bridge circuit comprises a third series circuit of a fifth magnetoresistance and a sixth magnetoresistance connected in parallel with the first series circuit. The second bridge circuit comprises a fourth series circuit of a seventh magnetoresistance and an eighth magnetoresistance connected in parallel with the second series circuit. The method may further comprise coupling a third terminal between the fifth and sixth magnetoresistances of the first bridge circuit to a fourth terminal between the seventh and eighth magnetoresistances of the second bridge circuit and providing a second output signal of the magnetic field sensor circuit at the coupled third and fourth terminals.

[0024] In some embodiments, the first series circuit of the first magnetoresistance and the second magnetoresistance may be coupled between a power supply and ground. The method may include switching between different sensing modes by modifying a power supply of the first and / or second series circuit.

[0025] In some embodiments, switching between different sensing modes comprises, in a first sensing mode, coupling the second series circuit of the third magnetoresistance and the fourth magnetoresistance between the power supply and ground, in a second sensing mode, switching the terminals of the power supply and ground for the second series circuit compared to the first sensing mode, and / or in a third sensing mode, coupling the second series circuit of the third magnetoresistance and the fourth magnetoresistance between two ground terminals.

[0026] The present disclosure proposes a dual-bridge approach to address differential sensing on a power rail. Furthermore, by grounding one of the bridges, it can be switched to the other sensing mode and is sensitive to homogeneous fields. This could be done permanently or even with a user command to enable measurement of both signals by a single sensor. Short description of the characters

[0027] Some examples of devices and / or methods are described below by way of example only and with reference to the accompanying figures, in which Fig. 1A-D show various magnetic sensing concepts for current sensing and speed sensing to which the present disclosure may be applied; Fig. Figure 2A shows a conventional sensor (full) bridge configuration; Fig. 2B the conventional sensor bridge configuration of Fig. 2A, which is coupled to a differential amplifier circuit; Fig. Figure 2C shows a conventional sensor (half-)bridge configuration coupled to an amplifier circuit; Fig. 3A shows a sensor bridge configuration according to a first embodiment; Fig. 3B shows a sensor bridge configuration according to a second embodiment; Fig. 3C shows a sensor bridge configuration according to a third embodiment; and Fig. 4 shows a sensor bridge configuration with amplifiers for output signal amplification. Detailed description

[0028] Some examples will now be described in more detail with reference to the accompanying figures. However, other possible examples are not limited to the features of these detailed embodiments. Other examples may include modifications of the features, as well as equivalents and alternatives to the features. Furthermore, the terminology used herein to describe specific examples is not intended to be limiting of other possible examples.

[0029] Throughout the description of the figures, identical or similar reference numerals refer to identical or similar elements and / or features, which may be implemented identically or in a modified form while providing the same or a similar function. Furthermore, in the figures, the thicknesses of lines, layers, and / or regions may be exaggerated for clarity.

[0030] When two elements A and B are combined using "or," this is to be understood as disclosing all possible combinations, i.e., only A, only B, and A and B, unless explicitly defined otherwise in the individual case. Alternative wording for the same combinations may be "at least one of A and B" or "A and / or B." This applies accordingly to combinations of more than two elements.

[0031] If a singular form is used, such as "a," "an," and "the," and the use of only a single element is neither explicitly nor implicitly defined as mandatory, further examples may also use multiple elements to implement the same function. If a function is subsequently described as being implemented using multiple elements, further examples may implement the same function using a single element or a single processing entity.It is further understood that the terms "comprises", "comprising", "has" and / or "having" when used describe the presence of the specified features, integers, steps, operations, processes, elements, components and / or a group thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, processes, elements, components and / or a group thereof.

[0032] Fig. 1A-D illustrate various magnetic sensing concepts for current sensing and speed sensing applications to which embodiments of the present disclosure may be applied.

[0033] Fig. Figure 1A shows a first current sensing concept with a power rail or bus bar 110 arranged externally to a sensor chip or IC (integrated circuit) 120. In Fig. 1A, the sensor IC 120 comprises a single magnetic sensing element 122 and is arranged above the busbar 110 for homogeneous magnetic field sensing. The sensing element 122 may, for example, comprise a (full) Wheatstone bridge arrangement of four magnetoresistive elements. The magnetoresistive elements may also be referred to as XMR elements.

[0034] Fig. 1B shows a second current sensing concept with a busbar 110 arranged externally to the sensor IC 120. The sensor IC 120 includes a first sensing element 122-1 arranged above the busbar 110 and a second sensing element 122-2 arranged adjacent to the first sensing element 122-1 and also adjacent to the busbar 110 for differential magnetic field sensing. Both sensing elements 122-1, 122-2 can, for example, comprise a respective (full) Wheatstone bridge arrangement of four magnetoresistances.

[0035] Fig. Figure 1C shows a third current sensing concept with a busbar 110 arranged externally to the sensor IC 120. The sensor IC 120 includes a first sensing element 122-1 arranged above the busbar 110 and a second sensing element 122-2 arranged adjacent to the first sensing element 122-1 but also above the busbar 110 for differential magnetic field sensing. In the example of Fig. 1C, the busbar 110 includes a slot 112 over which the sensor IC 120 is placed. The first sensing element 122-1 can measure the magnetic field due to the current through the busbar 110 to the left of the slot 112, and the second sensing element 122-2 can measure the magnetic field due to the current through the busbar 110 to the right of the slot 112. Both sensing elements 122-1, 122-2 can, for example, comprise a respective Wheatstone bridge arrangement of four magnetoresistances.

[0036] Fig. Figure 1D illustrates a magnetic speed sensing application in which differential sensing is used to detect the speed and direction of rotation of a toothed ferrite wheel 130 or a wheel with magnetic domains. The sensor IC 120 is arranged radially outward of the wheel 130 and includes two adjacent sensing elements 122-1, 122-2 for differential field sensing. Both sensing elements 122-1, 122-2 may, for example, comprise a respective Wheatstone bridge arrangement of four magnetoresistances.

[0037] Fig. Figure 2A illustrates a conventional sensor IC 120 having a first magnetic sensing element 122-1 implemented as a first bridge circuit and an adjacent second magnetic sensing element 122-2 implemented as a second bridge circuit. In the illustrated example, the first and second bridge circuits 122-1, 122-2 are each implemented as full Wheatstone bridges to provide respective differential output signals V left [left = left] and V right[right = right]. Those skilled in the art, having benefit from the present disclosure, will recognize that the first and second bridge circuits 122-1, 122-2 could also be implemented as half Wheatstone bridges if asymmetric output signals are sufficient. While a half Wheatstone bridge consists only of a single series circuit of a first resistor and a second resistor, a full Wheatstone bridge includes a first series circuit of a first magnetoresistance and a second magnetoresistance connected in parallel with a second series circuit of a third resistor and a fourth resistor.

[0038] The Fig. The first bridge circuit 122-1 shown in Figure 2A (left) comprises a first series circuit of a first magnetic resistor R1 and a second magnetic resistor R2, which are coupled between a first power supply terminal 202-1 and a first ground terminal 204-1. The first power supply terminal 202-1 is directly coupled to the second magnetic resistor R2. The first ground terminal 204-1 is directly coupled to the first magnetic resistor R1. The first bridge circuit 122-1 further comprises a second series circuit of a third magnetic resistor R3 and a fourth magnetic resistor R4, which are coupled between the first power supply terminal 202-1 and the first ground terminal 204-1 in parallel with the first series circuit. The first power supply terminal 202-1 is directly coupled to the fourth magnetic resistor R4. The first ground terminal 204-1 is directly coupled to the third magnetic resistor R3.

[0039] The first magnetoresistance R1 comprises a first reference magnetization (here: to the left), the second magnetoresistance R2 comprises a second reference magnetization (here: to the right) that differs from the first reference magnetization. The second reference magnetization of the second magnetoresistance R2 can be antiparallel (i.e., 180°) to the first reference magnetization of the first magnetoresistance R1. The third magnetoresistance R3 comprises the second reference magnetization (to the right), and the fourth magnetoresistance R4 comprises the first reference magnetization (to the left). A first differential output signal (V left ) of the first bridge circuit 122-1 is connected between a first output terminal (V left + ) between the first and second magnetic resistors R1, R2 and a second output terminal (V left - ) between the third and fourth magnetic resistors R3, R4.

[0040] The Fig. The second bridge circuit 122-2 shown in Figure 2A (right) includes a third series circuit of a fifth magnetic resistor R5 and a sixth magnetic resistor R6 coupled between a second power supply terminal 202-2 and a second ground terminal 204-2. The second power supply terminal 202-2 is directly coupled to the sixth magnetic resistor R6. The second ground terminal 204-2 is directly coupled to the fifth magnetic resistor R5. The second bridge circuit 122-2 further includes a fourth series circuit of a seventh magnetic resistor R7 and an eighth magnetic resistor R8 coupled between the second power supply terminal 202-2 and the second ground terminal 204-2 in parallel with the third series circuit. The second power supply terminal 202-2 is directly coupled to the eighth magnetic resistor R8. The second ground terminal 204-2 is directly coupled to the seventh magnetic resistor R7.

[0041] The fifth magnetoresistance R5 comprises the first reference magnetization (here: to the left), the sixth magnetoresistance R6 comprises the second reference magnetization (here: to the right), which differs from the first reference magnetization. The seventh magnetoresistance R7 comprises the second reference magnetization, and the eighth magnetoresistance R8 comprises the first reference magnetization. A second differential output signal (V right ) of the second bridge circuit 122-2 is connected between a third output terminal (V right + ) between the fifth and sixth magnetoresistances R5, R6 and a fourth output terminal (V right - ) between the seventh and eighth magnetic resistors R7, R8.

[0042] Magnetoresistances R1 to R8 are a type of electronic component whose electrical resistance changes in response to an applied external magnetic field. Some examples of magnetoresistances that can be used are: Anisotropic magnetoresistive (AMR) elements: AMR elements utilize the anisotropic magnetoresistance effect, whereby the electrical resistance of a material changes with the direction of an applied magnetic field. They are commonly used in magnetic field sensing applications such as compasses, position sensors, and contactless current sensing.

[0043] Giant magnetoresistive (GMR) elements: GMR elements exploit the giant magnetoresistance effect that occurs in layered structures of magnetic and non-magnetic materials. GMR sensors offer higher sensitivity and lower power consumption compared to AMR sensors. They are used in applications such as magnetic field sensing, data storage devices (read heads in hard disk drives), and magnetic field imaging.

[0044] Tunnel magnetoresistive (TMR) elements: TMR elements utilize the tunnel magnetoresistance effect, where the electrical resistance changes based on the relative orientation of the magnetic layers separated by a thin insulating barrier. TMR sensors exhibit high sensitivity and low power consumption, making them suitable for applications such as magnetic field sensing, spintronics, and magnetic random access memory (MRAM).

[0045] Preferably, all magnetic resistors R1 to R8 are of the same type, e.g., AMR type, GMR type, or TMR type.

[0046] In the context of magnetoresistive elements, or magnetoresistive elements, "reference magnetization" refers to the orientation or alignment of the magnetic field in a specific direction, which serves as a reference for measuring changes in resistance caused by an external magnetic field. Magnetoresistive elements, such as AMR, GMR, or TMR magnetoresistive elements, exhibit a change in electrical resistance in response to the orientation of an applied external magnetic field. This change in resistance is commonly referred to as the magnetoresistive effect. To measure magnetoresistance, a reference magnetization is established within the magnetoresistive element. The reference magnetization provides a baseline against which changes in resistance can be detected.In a typical configuration, the magnetoresistance comprises multiple layers, including magnetic layers and non-magnetic spacer layers. The reference magnetization is established within one of these layers or in an adjacent magnet or synthetic antiferromagnet. The direction of the reference magnetization remains fixed, allowing the detection of changes in resistance caused by an external magnetic field. When an external magnetic field is applied to the magnetoresistance, the magnetoresistance's magnetization can align or deviate from the reference magnetization, resulting in a change in resistance. This change in resistance can then be measured and quantified, providing information about the magnitude, direction, or other characteristics of the external magnetic field.In summary, the reference magnetization in magnetoresistances provides a fixed orientation of the magnetic field within the element, which serves as a reference for measuring resistance changes induced by an external magnetic field. It enables the detection and quantification of magnetic field variations by measuring the magnetoresistance.

[0047] The example of Fig. Figure 2A shows two fully independent sensing element bridges 122-1, 122-2 with independent differential voltages V left , V right . The differential voltages V left , V right can also be fed to one or more amplifier stages 210 or to further processing. This is Fig. 2B. As previously mentioned, the first and second bridge circuits 122-1, 122-2 could also be implemented as half Wheatstone bridges if asymmetric output signals are sufficient. One such example is shown in Fig. 2C illustrates.

[0048] The sensitivity to differential magnetic fields of the architecture of Fig. 2A can be expressed as Vdiff(Bsig)=−VDDS⋅SB⋅Bsig where VDDS denotes the supply voltage at the first and second power supply terminals 202-1, 202-2, S B the sensitivity of the bridge circuits 122-1, 122-2 and · B sig the strength of the external differential magnetic field.

[0049] The sensitivity to homogeneous fields of the architectures of Fig. 2A- Fig. 2C is zero.

[0050] To provide magnetic field sensor circuits that can be used to measure both homogeneous magnetic fields and differential magnetic fields, the present disclosure proposes connecting the two bridge circuits 122-1, 122-2. Various examples of resulting magnetic field sensor circuits are shown in Fig. 3A to Fig. Shown in 3D.

[0051] A first embodiment of a magnetic field sensor circuit 300 with interconnected bridge circuits 122-1, 122-2 is shown in Fig. 3A shown.

[0052] The magnetic field sensor circuit 300 of Fig. 3A differs from the magnetic field sensor circuit 120 of Fig. 2A in that the first output terminal between the first magnetic resistor R1 and the second magnetic resistor R2 (of the first bridge circuit 122-1) and the fourth output terminal between the seventh magnetic resistor R7 and the eighth magnetic resistor R8 (of the second bridge circuit 122-2) are (directly) coupled or connected to each other. In other words, the first output terminal and the fourth output terminal are short-circuited. The coupled first and fourth output terminals provide a first output signal Vn of the magnetic field sensor circuit 300. Similarly, the second output terminal between the third magnetic resistor R3 and the fourth magnetic resistor R4 (of the first bridge circuit 122-1) and the third output terminal between the fifth magnetic resistor R5 and the sixth magnetic resistor R6 (of the second bridge circuit 122-2) are (directly) coupled or connected to each other.In other words, the second output terminal and the third output terminal are short-circuited. The coupled second and third output terminals provide a second output signal Vp of the magnetic field sensor circuit 300. As can be seen, the branches of the different bridge circuits 122-1, 122-2, which have different (antiparallel) reference magnetizations, are connected or coupled to each other. Those skilled in the art, benefiting from the present disclosure, will again recognize that the first and second bridge circuits 122-1, 122-2 could also be implemented as (directly) coupled or interconnected half Wheatstone bridges if asymmetric output signals are sufficient.

[0053] The sensitivity to differential magnetic fields of the architecture of Fig. 3A can be expressed as Vdiff(Bsig)=−VDDS⋅SB2Bsig

[0054] Thus, the sensitivity to differential fields of the architecture of Fig. 2B half the sensitivity to differential fields of the architecture of Fig. 2A. The architecture of Fig. However, 3A can offer several advantages over the architecture of Fig. 2A, which will be seen below.

[0055] The sensitivity to homogeneous fields of the architecture of Fig. 3A can be expressed as Vdiff(Bhom)=VR⋅SBR−VL⋅SBL2Bhom where V L the supply voltage at the left power supply terminal 202-1, V R the supply voltage at the right power supply terminal 202-2, S BL the sensitivity of the left bridge circuit 122-1, S BR the sensitivity of the right bridge circuit 122-2 and B homis the strength of the external homogeneous magnetic field. Since V R = V L = VDDS and equal sensitivities S BL = S BR are, the sensitivity to homogeneous fields is zero. Thus, if the sensitivities of the left and right bridges 122-1, 122-2 are equal, the sensitivity to homogeneous fields is zero and the sensing element arrangement of Fig. 3A is only sensitive to differential fields.

[0056] To implement a homogeneous field sensor with the proposed interconnected bridge arrangement, one of the bridge power supplies can be flipped to have a completely homogeneous sensor. This is shown in Fig. 3B shown.

[0057] The magnetic field sensor circuit 300 of Fig. 3B differs from Fig. 3A in that the supply voltage VDDS of the right bridge circuit 122-2 is coupled to the lower terminal 204-2 and ground is coupled to the upper terminal 202-2, while in Fig. 3A, the supply voltage VDDS is coupled to the upper terminal 202-2 and ground is coupled to the lower terminal 204-2. This means that the supply of the right bridge circuit 122-2 is with respect to Fig. 3A flipped. In Fig. 3B, ground is directly coupled to the sixth magnetoresistance R6 and the eighth magnetoresistance R8, and the power supply is directly coupled to the fifth magnetoresistance R5 and the seventh magnetoresistance R7.

[0058] The sensitivity to differential fields of the architecture of Fig. 3B can be expressed as Vdiff(Bsig)=VR⋅SBR−VL⋅SBL4Bsig

[0059] Thus, if the sensitivities of the left and right bridge circuits 122-1, 122-2 are equal, the sensitivity to differential fields is zero and the sensing element array is only sensitive to homogeneous fields.

[0060] The sensitivity to homogeneous fields of the architecture of Fig. 3B can be expressed as Vdiff(Bhom)=−VDDS⋅SB1Bhom

[0061] Thus, if the individual bridge sensitivities of the left and right bridges are equal, the differential sensitivities cancel each other out, leaving only a sensitivity to homogeneous fields. Switches can be implemented in the supply path to switch between the sensing element arrays of Fig. 3A and Fig. 3B. For the purpose of flipping the supply of the second bridge circuit 122-2 between Fig. 3A and Fig. 3B, the magnetic field sensor circuit 300 may include a switch circuit configured to couple the lower terminal 204-2 of the second bridge circuit 122-2 to the power supply and the upper terminal 202-2 of the bridge circuit 122-2 to ground in a first sensing mode (homogeneous field sensing mode). The switch circuit may also be configured to couple the lower terminal 204-2 of the second bridge circuit 122-2 to ground and the upper terminal 202-2 of the bridge circuit 122-2 to the power supply VDDS in a second sensing mode (differential field sensing mode).

[0062] A further third detection mode will now be described with reference to Fig. 3C. The magnetic field sensor circuit 300 of Fig. 3C differs from Fig. 3A and Fig. 3B in that ground is coupled to both the upper supply terminal 202-2 and the lower supply terminal 204-2 of the right bridge circuit 122-2, while in Fig. 3A and Fig. 3B, the supply voltage VDDS is coupled to one of the terminals 202-2, 204-2. In Fig. 3C ground is directly coupled to the sixth magnetoresistance R6 and the eighth magnetoresistance R8, and ground is also directly coupled to the fifth magnetoresistance R5 and the seventh magnetoresistance R7.

[0063] By applying ground to the supply of one of the bridges 122-2, it can be easily seen that the detection arrangement is sensitive to both differential and homogeneous fields. This ground of one of the bridges 122-1, 122-2 is easy to implement.

[0064] The sensitivity to differential fields of the architecture of Fig. 3C can be expressed as Vdiff(Bsig)=−VDDS⋅SB4Bsig

[0065] The sensitivity to homogeneous fields of the architecture of Fig. 3C can be expressed as Vdiff(Bhom)=−VDDS⋅SB2Bhom

[0066] For the purpose of flipping the configuration of the magnetic field sensor circuit 200 between Fig. 3A to Fig. 3C, the magnetic field sensor circuit 200 may include a switch circuit configured to couple both the lower terminal 204-2 and the upper terminal 202-2 of the second bridge circuit 122-2 to ground in a third sensing mode (differential + homogeneous field sensing mode). The switch circuit may also be configured to couple the lower terminal 204-2 of the second bridge circuit 122-2 to ground and the upper terminal 202-2 of the bridge circuit 122-2 to the power supply VDDS in the second sensing mode (differential field sensing mode). The switch circuit may also be configured to couple the lower terminal 204-2 of the second bridge circuit 122-2 to the power supply voltage VDDS and the upper terminal 202-2 of the bridge circuit 122-2 to ground in the first sensing mode (homogeneous field sensing mode).

[0067] Those skilled in the art having benefit of the present disclosure will appreciate that the magnetic field sensor circuits 300 of Fig. 3A, Fig. 3B and Fig. 3C may occur as standalone magnetic field sensor circuits 200 or may be combined via the mentioned switch circuit arrangement, which is configured to switch between the various magnetic field sensor circuit arrangements.

[0068] The examples of Fig. 3A to Fig. 3C show two interconnected sensing element bridges 122-1, 122-2 with a differential output voltage (V n , V p ). The differential output voltage can also be fed to one or more amplifier stages 210 or to further processing. This is described in Fig.4, where a first input terminal of the differential amplifier 210-1 is coupled to the first output signal (Vn) and a second input terminal of the differential amplifier 210-1 is coupled to the second output signal (Vp).

[0069] As previously mentioned, the interconnected first and second bridge circuits 122-1, 122-2 could also be implemented as half Wheatstone bridges if asymmetric output signals are sufficient.

[0070] The present disclosure describes an architecture with a simple solution for creating a differential sensor or a homogeneous field sensor. This could be used in a user system to either provide the user with full flexibility to select the same sensor for different applications and configure the sensor according to the required measurement principle. On the other hand, this capability could also be used to continuously measure superimposed homogeneous fields and compensate for their effects in a differential measurement problem.

[0071] The present disclosure proposes an interconnected dual bridge sensing element arrangement that enables a simple and efficient architecture of the sensor electronics in combination with the ability to employ different operating modes on the bridge configuration.

[0072] The aspects and features described in connection with a particular one of the previous examples may also be combined with one or more of the further examples to replace an identical or similar feature of that further example or to additionally introduce the feature into the further example.

[0073] It is further understood that the disclosure of multiple steps, processes, operations, or functions disclosed in the specification or claims should not be construed as necessarily being in the described order, unless explicitly stated in the individual case or absolutely necessary for technical reasons. Therefore, the foregoing description does not limit the performance of multiple steps or functions to any particular order. Furthermore, in further examples, a single step, function, process, or operation may include and / or be broken down into multiple sub-steps, functions, processes, or operations.

[0074] If some aspects are described in the context of a device or system, these aspects are also to be understood as a description of the corresponding method. For example, a block, device, or functional aspect of the device or system may correspond to a feature, such as a method step, of the corresponding method. Accordingly, aspects described in the context of a method are also to be understood as a description of a corresponding block, element, property, or functional feature of a corresponding device or system.

[0075] The following claims are hereby incorporated into the Detailed Description, and each claim may stand on its own as a separate example. It should also be noted that although a dependent claim in the claims refers to a particular combination with one or more other claims, other examples may include a combination of the dependent claim with the subject matter of any other dependent or independent claim. Such combinations are hereby explicitly contemplated unless it is specifically stated that a particular combination is not intended. Furthermore, features of a claim for any other independent claim are also intended to be encompassed, even if that claim is not directly defined as dependent on that other independent claim.

Claims

[1] A magnetic field sensor circuit (300) comprising a first bridge circuit (122-1) comprising a first series circuit of a first magnetic resistor (R1) and a second magnetic resistor (R2); a second bridge circuit (122-2) comprising a second series circuit of a third magnetoresistance (R7) and a fourth magnetoresistance (R8), wherein a first terminal between the first magnetic resistor (R1) and the second magnetic resistor (R2) of the first bridge circuit (122-1) is coupled to a second terminal between the third magnetic resistor (R7) and the fourth magnetic resistor (R8) of the second bridge circuit (122-2), and wherein the coupled first and second terminals provide a first output signal of the magnetic field sensor circuit (300). [2] The magnetic field sensor circuit (300) of claim 1, wherein the first and second terminals are short-circuited. [3] The magnetic field sensor circuit (300) according to any one of the preceding claims, wherein the first series circuit of the first magnetic resistor (R1) and the second magnetic resistor (R2) is coupled between a first power supply terminal (202-1) and a first ground terminal (204-1); the second series circuit of the third magnetic resistor (R7) and the fourth magnetic resistor (R8) is coupled between a second power supply terminal (202-2; 204-2) and a second ground terminal (204-2; 202-2). [4] The magnetic field sensor circuit (300) of claim 3, wherein the first power supply terminal (202-1) is coupled to a magnetoresistance (R2) of the first series circuit having a first reference magnetization, and the second power supply terminal (202-2) is coupled to a magnetoresistance (R8) of the second series circuit having a second reference magnetization different from the first reference magnetization. [5] The magnetic field sensor circuit (300) of claim 4, wherein the second reference magnetization is antiparallel to the first reference magnetization. [6] The magnetic field sensor circuit (300) of claim 3, wherein the first power supply terminal (202-1) is coupled to a magnetoresistance (R2) of the first series circuit having a first reference magnetization, and the second power supply terminal (204-2) is coupled to a magnetoresistance (R7) of the second series circuit having the first reference magnetization. [7] The magnetic field sensor circuit (300) according to claim 1 or 2, wherein the first series circuit of the first magnetic resistor (R1) and the second magnetic resistor (R2) is coupled between a first power supply terminal (202-1) and a first ground terminal (204-1); the second series circuit of the third magnetic resistor (R7) and the fourth magnetic resistor (R8) is coupled between a second ground terminal (202-2; 204-2) and a third ground terminal (204-2; 202-2). [8] The magnetic field sensor circuit (300) according to any one of the preceding claims, wherein the first series circuit of the first magnetoresistance (R1) and the second magnetoresistance (R2) is coupled between a power supply and ground, the magnetic field sensor circuit (300) further comprising a switch circuit configured to switch between different sensing modes by modifying a power supply of the first or the second series circuit. [9] The magnetic field sensor circuit (300) according to claim 8, wherein the switch circuit is configured to in a first detection mode, coupling the second series circuit of the third magnetoresistance and the fourth magnetoresistance between the power supply and ground; in a second detection mode, switching the power supply and ground connections for the second series circuit compared to the first detection mode; or in a third detection mode, to couple the second series circuit of the third magnetoresistance and the fourth magnetoresistance between two ground terminals. [10] The magnetic field sensor circuit (300) according to any one of the preceding claims, wherein the first series circuit of the first magnetoresistance (R1) and the second magnetoresistance (R2) is coupled between a power supply and ground, the magnetic field sensor circuit (300) further comprising: a switch circuit configured to in a first detection mode, coupling the second series circuit of the third magnetoresistance (R7) and the fourth magnetoresistance (R8) between the power supply and ground; in a second detection mode, switching the power supply and ground connections for the second series circuit compared to the first detection mode; or in a third detection mode, to couple the second series circuit of the third magnetoresistance (R7) and the fourth magnetoresistance (R8) between two ground terminals. [11] The magnetic field sensor circuit (300) according to any one of the preceding claims, wherein the first magnetoresistance (R1) of the first bridge circuit comprises a first reference magnetization, the second magnetoresistance (R2) of the first bridge circuit comprises a second reference magnetization which differs from the first reference magnetization, the third magnetoresistance (R7) of the second bridge circuit comprises the second reference magnetization, and the fourth magnetoresistance (R8) of the second bridge circuit comprises the first reference magnetization. [12] The magnetic field sensor circuit (300) of claim 11, wherein the second reference magnetization is antiparallel to the first reference magnetization. [13] The magnetic field sensor circuit (300) according to any one of the preceding claims, wherein the first bridge circuit (122-1) comprises a third series circuit of a fifth magnetoresistance and a sixth magnetoresistance connected in parallel to the first series circuit; the second bridge circuit (122-2) comprises a fourth series circuit of a seventh magnetoresistance and an eighth magnetoresistance connected in parallel to the second series circuit; wherein a third terminal between the fifth and sixth magnetoresistances of the first bridge circuit is coupled to a fourth terminal between the seventh and eighth magnetoresistances of the second bridge circuit, and wherein the coupled third and fourth terminals provide a second output signal of the magnetic field sensor circuit. [14] The magnetic field sensor circuit (300) of claim 13, wherein the third and fourth terminals are short-circuited. [15] The magnetic field sensor circuit (300) according to claim 11 and 13, wherein the fifth magnetoresistance of the first bridge circuit comprises the second reference magnetization, the sixth magnetoresistance of the first bridge circuit comprises the first reference magnetization, the seventh magnetoresistance of the second bridge circuit comprises the first reference magnetization, and the eighth magnetoresistance of the second bridge circuit comprises the second reference magnetization. [16] The magnetic field sensor circuit (300) according to any one of claims 13 to 15, further comprising a differential amplifier (210), wherein a first input terminal of the differential amplifier (210) is coupled to the first output signal, and a second input terminal of the differential amplifier (210) is coupled to the second output signal. [17] The magnetic field sensor circuit (300) according to any one of the preceding claims, wherein the magnetoresistances of the first and second bridge circuits (122-1; 122-2) are giant magnetoresistances, GMR, or tunnel magnetoresistances, TMR. [18] A magnetic field measurement method comprising Providing a first bridge circuit comprising a first series circuit of a first magnetoresistance and a second magnetoresistance; Providing a second bridge circuit comprising a second series circuit of a third magnetoresistance and a fourth magnetoresistance, Coupling a first terminal between the first and second magnetoresistances of the first bridge circuit to a second terminal between the third and fourth magnetoresistances of the second bridge circuit, and Providing an output signal of the magnetic field sensor circuit at the coupled first and second terminals. [19] The method of claim 18, wherein the first bridge circuit comprises a third series circuit of a fifth magnetoresistance and a sixth magnetoresistance connected in parallel to the first series circuit; the second bridge circuit comprises a fourth series circuit of a seventh magnetoresistance and an eighth magnetoresistance connected in parallel to the second series circuit; Coupling a third terminal between the fifth and sixth magnetoresistances of the first bridge circuit to a fourth terminal between the seventh and eighth magnetoresistances of the second bridge circuit; and Providing a second output signal of the magnetic field sensor circuit at the coupled third and fourth terminals. [20] The method according to claim 18 or 19, comprising coupling the first series circuit of the first magnetoresistance and the second magnetoresistance between a power supply and ground; and Switching between different sensing modes by modifying a power supply of the first or second series circuit. [21] The method of claim 20, wherein switching comprises in a first detection mode, coupling the second series circuit of the third magnetoresistance and the fourth magnetoresistance between the power supply and ground; in a second detection mode, switching the power supply and ground connections for the second series circuit compared to the first detection mode; or in a third detection mode, coupling the second series circuit of the third magnetoresistance and the fourth magnetoresistance between two ground terminals.

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