Linear bridges with nonlinear elements for operation at high magnetic field strengths.

Abstract

In one embodiment, the bridge includes a first magnetoresistive element having a first reference angle, a second magnetoresistive element in series with the first magnetoresistive element having a second reference angle, a third magnetoresistive element in parallel with the first magnetoresistive element having the first reference angle, and a fourth magnetoresistive element in series with the third magnetoresistive element having the second reference angle. The output of the bridge has a linear response over a range of horizontal magnetic field values ​​having non-zero values, with horizontal magnetic field strength values ​​in the range associated with vertical magnetic field strength values ​​having zero Oersted (Oe) values. The reference angle indicates the angle at which the magnetoresistive elements are most sensitive to changes in the magnetic field.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation-in-part (CIP) of U.S. patent application Ser. No. 16 / 822,488, filed March 18, 2020, entitled "LINEAR BRIDGES HAVING NONLINEAR ELEMENTS," which claims the benefit of and priority to that U.S. patent application, and is incorporated herein by reference in its entirety. [Background technology]

[0002] The term "magnetic field sensing element" is used to describe various electronic elements capable of sensing magnetic fields. The magnetic field sensing element may be, but is not limited to, a Hall effect element, a magnetoresistive element, or a magnetotransistor. As is known, there are different types of Hall effect elements, such as planar Hall elements, vertical Hall elements, and circular vertical Hall (CVH) elements. Furthermore, as is known, there are different types of magnetoresistive elements, such as semiconductor magnetoresistive elements such as indium antimonide (InSb), giant magnetoresistive (GMR) elements, anisotropic magnetoresistive (AMR) elements, tunneling magnetoresistive (TMR) elements, and magnetic tunnel junctions (MTJs). A magnetic field sensing element may be a single element or, alternatively, may include two or more magnetic field sensing elements arranged in various configurations, such as a half bridge or a full (Wheatstone) bridge. Depending on the device type and other application requirements, the magnetic field sensing element may be a device made from type IV semiconductor materials such as silicon (Si) or germanium (Ge), or type III-V semiconductor materials such as gallium arsenide (GaAs) or indium compounds such as indium antimonide (InSb).

[0003]

[0003] As is known, some of the magnetic field sensing elements described above tend to have their maximum sensitivity axis parallel to the substrate supporting the magnetic field sensing element, and other of the magnetic field sensing elements described above tend to have their maximum sensitivity axis perpendicular to the substrate supporting the magnetic field sensing element. In particular, planar Hall elements tend to have their sensitivity axis perpendicular to the substrate, while metallic or metallic magnetoresistive elements (e.g., GMR, TMR, AMR) and vertical Hall elements tend to have their sensitivity axis parallel to the substrate. Summary of the Invention

[0004] In one aspect, the bridge includes a first magnetoresistive element having a first reference angle, a second magnetoresistive element in series with the first magnetoresistive element having a second reference angle, a third magnetoresistive element in parallel with the first magnetoresistive element having the first reference angle, and a fourth magnetoresistive element in series with the third magnetoresistive element having the second reference angle. The output of the bridge has a linear response over a range of horizontal magnetic field values ​​having non-zero values, the range of horizontal magnetic field strength values ​​being zero Oersteds (Oe). (0A / m) The reference angle is associated with a perpendicular magnetic field strength value having a value of 0.055. The reference angle indicates the angle at which the magnetoresistive element is most sensitive to changes in the magnetic field.

[0005] The above aspects may include one or more of the following features. 2. The first, second, third, and fourth magnetoresistance elements may each be a giant magnetoresistance (GMR) element or a tunneling magnetoresistance (TMR) element. The bridge may include a fifth magnetoresistance element in series with the first magnetoresistance element and having a third reference angle, and a sixth magnetoresistance element in series with the third magnetoresistance element and having a third reference angle. The fifth and sixth magnetoresistance elements may be configured to be the same. The fifth and sixth magnetoresistance elements may be configured with the same number of pillars. The number of pillars in each of the first, second, third, fourth, fifth, and sixth magnetoresistance elements and the first, second, and third reference angles may be selected to enable the bridge to generate a linear output with a controlled offset over a temperature range of 10°C to 100°C. The first and second reference angles may enable the bridge output to have a linear response over a range of horizontal magnetic field strength values ​​having non-zero values. The first and second reference angles may enable the bridge output to have a linear response over a range of horizontal magnetic field strength values ​​that does not include zero values. The first and third magnetoresistive elements may be configured to be identical. The first and third magnetoresistive elements may be configured with the same number of pillars. The second and fourth magnetoresistive elements may be configured to be identical. The second and fourth magnetoresistive elements may be configured with the same number of pillars. The linear response may be greater than 200 Oe. (15915A / m) The linear response can be over a range including horizontal magnetic field values ​​of 300 Oe and above. (23873A / m) The reference angle may be approximately perpendicular to the second reference angle. The reference angle may be approximately perpendicular to the magnetic field sensed by the sensor.

[0006] In another aspect, a camera includes a magnetic field sensor including a bridge. The bridge includes a first magnetoresistive element having a first reference angle, a second magnetoresistive element in series with the first magnetoresistive element having a second reference angle, a third magnetoresistive element in parallel with the first magnetoresistive element having the first reference angle, and a fourth magnetoresistive element in series with the third magnetoresistive element having the second reference angle. The output of the bridge has a linear response over a range of horizontal magnetic field strength values ​​having non-zero values, the range of horizontal magnetic field strength values ​​being zero Oersteds (Oe). (0A / m) The reference angle is associated with a perpendicular magnetic field strength value having a value of 0.055. The reference angle indicates the angle at which the magnetoresistive element is most sensitive to changes in the magnetic field.

[0007] The above aspect may include one or more of the following features: the camera may be disposed within the cellular device; the camera may further include a magnetic target, a focus controller, and a lens, wherein movement of the magnetic target provides an output to the focus controller to vary the focal length of the lens; Ruta Therefore, it can be detected by a magnetic field sensor.

[0008]

[0008] The above-described features can be more fully understood from the following description of the drawings. The drawings aid in explaining and understanding the disclosed technology. Because it is often impractical or impossible to illustrate and describe every possible embodiment, the figures provided represent one or more exemplary embodiments. As such, the figures are not intended to limit the scope of the broad concepts, systems, and technologies described herein. Like numbers in the figures indicate like components. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a graph illustrating a magnetic field trajectory for a linear magnetic field sensor. [Figure 2]

[0010] FIG. 1 is a block diagram of a prior art example of a tunneling magnetoresistive (TMR) element. [Figure 3]

[0011] 1 is a graph illustrating a linear trajectory of a magnetic field for a bridge including magnetoresistive (MR) elements. [Figure 4]

[0012] FIG. 1 is a circuit diagram of an example of a bridge including an MR element. [Figure 5]

[0013] FIG. 1 is a flow diagram of an example process for determining a reference angle for an MR element. [Figure 6A]

[0014] 1 is a graph of an example of a magnetic field trajectory. [Figure 6B]

[0015] 10 is a graph of another example of a magnetic field trajectory. [Figure 7]

[0016] 1 is a graph illustrating the resistance of an MR element with respect to the trajectory of a magnetic field. [Figure 8]

[0017] 10 is a graph illustrating magnetic field trajectories with zero offset for a bridge including MR elements. [Figure 9]

[0018] FIG. 1 is a circuit diagram of an example of a bridge including MR elements used to generate a linear response with zero voltage. [Figure 10]

[0019] 10 is a graph of an example output of the bridge in FIG. 9. [Figure 11]

[0020] FIG. 10 is a flow diagram of an example process for a reference angle for a third type of MR element in the bridge of FIG. 9. [Figure 12]

[0021] FIG. 12 is a block diagram of an example computer on which any of the processes of FIGS. 5 and / or 11 may be implemented. [Figure 13]

[0022] 1 is a graph illustrating a magnetic field trajectory without an external magnetic field bias. [Figure 14]

[0023] 14 is a graph of an example response of a tunneling magnetoresistive (TMR) element when the reference direction is aligned with the HX axis as represented in FIG. 13. [Figure 15]

[0024] 14 is a graph of an example response of a TMR when the reference direction is perpendicular to the HX axis as represented in FIG. 13. [Figure 16]

[0025] FIG. 14 is a circuit diagram of an example of a linear bridge used to detect the magnetic field trajectory of FIG. 13. [Figure 17]

[0026] 17 is a graph of an example output of the bridge of FIG. 16. [Figure 18A]

[0027] 14 is a circuit diagram of another example of a linear bridge for detecting the trajectory of the magnetic field in FIG. 13. FIG. [Figure 18B]

[0028] 18B is a graph of example reference directions for the MR elements in the bridge of FIG. 18A. [Figure 19]

[0029] 19A, 19B, and 19C are graphs of example resistance versus horizontal magnetic field strength values ​​at several different temperatures for the MR elements in the linear bridge of FIG. 18A. [Figure 20]

[0030] 18B is a graph of an example output of the linear bridge in FIG. 18A at various temperatures. [Figure 21]

[0031] 21 is a table illustrating the pillar numbers and reference directions used to obtain the graph in FIG. 20. [Figure 22]

[0032] FIG. 1 is a block diagram illustrating a camera including a bridge including an MR element. DETAILED DESCRIPTION OF THE INVENTION

[0010]

[0033] Described herein are techniques for fabricating bridges (linear bridges) for linear magnetometers using nonlinear magnetoresistive elements, such as giant magnetoresistive (GMR) or tunneling magnetoresistive (TMR) elements. In some examples, the techniques described herein can be used to construct linear magnetometers that are linear in magnetic field locus and range, where the magnetoresistive elements are typically not linear.

[0011]

[0034] Referring to Figure 1, a linear locus is a straight line in Hx and Hy space, where Hx represents horizontal magnetic field strength and Hy represents vertical magnetic field strength. Graph 100 shows the linear locus at Hx = 0 Oersteds (Oe). (0A / m) 10 includes an example of a linear trajectory from a linear magnetic field sensor centered at Hx = zero Oe. In one example, the linear trajectory 102 is (0A / m) The center is Hy=0Oe (0A / m) In another example, the linear locus 104 has Hx = zero Oe (0A / m) Hy=Hy ...

[0012]

[0035] As will be described further herein, TMR and GMR elements can be used to construct bridges with linear responses. For example, using the techniques described herein, the output of a bridge including TMR or GMR elements has a linear response with respect to horizontal magnetic fields.

[0013]

[0036] 2, an exemplary TMR element 200 may have a stack 202 of layers 206, 210, 214, 218, 222, 226, 228, and 232, which represent one pillar of a multi-pillar TMR element. Typically, layer 206 is a seed layer (e.g., a copper nickel (CuN) layer), and layer 210 is disposed on seed layer 206. Layer 210 may comprise, for example, platinum manganese (PtMn) or iridium manganese (IrMn). Layer 214 is disposed on layer 210, and layer 218 is disposed on layer 214. In one example, layer 214 comprises cobalt iron (CoFe), and layer 218 is a spacer layer and comprises ruthenium (Ru). On layer 218, a magnesium oxide (MgO) layer 226 is sandwiched between two cobalt iron boron (CoFeB) layers 222, 228. A cap layer 232 (e.g., tantalum (Ta)) is disposed on CoFeB layer 228. Layer 214 is a single-layer pinned layer that is magnetically coupled to layer 210. The physical mechanism that couples layers 210, 214 together is sometimes referred to as exchange bias.

[0014]

[0037] The free layer 230 includes a CoFeB layer 228. In some examples, the free layer 230 may include an additional layer (not shown) of nickel-iron (NiFe) and a thin layer of tantalum (not shown) between the CoFeB layer 228 and the NiFe layer.

[0015]

[0038] It will be understood that a drive current passing through TMR element 200 passes through the layers of the stack between seed layer 206 and cap layer 232, i.e., perpendicular to the surface of bottom electrode 204. TMR element 200 can have a maximum response axis that is parallel to the surface of bottom electrode 204 and along direction 229, and that is parallel to the magnetization direction of reference layer 250, which is comprised of layers 210, 214, 218, and 222 (among other things in layer CoFeB 222).

[0016]

[0039] The TMR element 200 has a maximum response axis (maximum response to an external field) oriented along arrow 229 and parallel to the magnetic field of the reference layer 250 (specifically, the pinned layer 222). Furthermore, it is generally the rotation of the magnetic orientation of the free layer 230 caused by an external magnetic field that results in a change in resistance of the TMR element 200, which can be attributed to an angular or amplitude change in the presence of an external bias, because the sum vector of the external field and bias causes an angular change between the reference and free layers.

[0017]

[0040] 3, TMR and GMR elements can be used to construct bridges with linear loci, but these loci are not centered on the vertical axis (Hy) and / or parallel to the sensor sensitivity axis. For example, linear loci 302 and linear loci 304 are not centered on the vertical axis (Hy axis). These linear loci can be used to construct bridges with outputs that have a linear response with respect to the horizontal magnetic field (Hx).

[0018]

[0041] 4, an example of a linear bridge is bridge 402. In one example, bridge 402 is a current-driven bridge.

[0019]

[0042] Bridge 402 includes magnetoresistive (MR) elements 404a, 404b, 406a, and 406b. Each of MR elements 404a, 404b, 406a, and 406b has a reference direction. For example, MR element 404a has reference direction 414a, MR element 404b has reference direction 414b, MR element 406a has reference direction 416a, and MR element 406b has reference direction 416b. As used herein, a reference direction (hereinafter sometimes referred to as a reference angle) indicates the direction in which an MR element is most sensitive to an external magnetic field.

[0020]

[0043] The MR element 404a and the MR element 404b are a first type of MR element, i.e., the MR elements 404a, 404b are electrically identical and their reference angles 414a, 414b are equal. The first type of MR element has a resistance R type1 It has.

[0021]

[0044] The MR element 406a and the MR element 406b are of a second type, i.e., the MR elements 406a, 406b are electrically identical and their reference angles 416a, 416b are equal. The second type of MR element has a resistance R type2 It has.

[0022]

[0045] As will be explained further herein, the reference angles 414a, 414b and the reference angles 416a, 416b are determined to achieve a bridge with an output that has a linear response. In an example, if the linear bridge 402 is a current-driven bridge, the output voltage of the bridge is Icc*(R type1 -R type2 ) where Icc is the current supplying bridge 402.

[0023]

[0046] In one example, where reference angles 414a, 414b and reference angles 416a, 416b are determined, the MR elements 404a, 404b may provide a majority of the signal from the linear bridge 402 by defining a reference direction, and the second type MR elements 406a, 406b may offset the nonlinearity of the second type MR elements 404a, 404b.

[0024]

[0047] 5, an example of a process for determining the reference angle is process 500. Process 500 measures the magnetic field response for the MR element at a number of different tilt angles (502).

[0025]

[0048] The process 500 determines (514) a value for each of the resistance combinations of the first and second type bridge MR elements. For example, the resistance combination may be the resistance of the first type MR element minus the resistance of the second type MR element (e.g., the resistance of MR element 404a minus the resistance of MR element 406a (see FIG. 4), i.e., (R type1 -R type2 ) Each resistor combination has a value. In one example, the value is a linear value ranging from zero to 100, where zero is the most linear value and 100 is the most nonlinear value.

[0026]

[0049] The process 500 selects 518 a value from among the resistor combination values ​​that represents the most linear response, for example, the linear value closest to zero.

[0027]

[0050] The process 500 selects 522 a reference angle for each type of bridge MR element that corresponds to the selected value. For example, the selected value from processing block 518 is a combination of associated resistances associated with the reference angles 414 a, 414 b for the first type MR elements 404 a, 404 b and the reference angles 416 a, 416 b for the second type MR elements 406 a, 406 b.

[0028]

[0051] 6A, graph 600 illustrates various examples of tilted and repeated magnetic field trajectories for an MR element. Each different tilt angle is associated with a different reference angle. For example, the tilted magnetic field trajectory is magnetic field trajectory 606 associated with a first reference angle. In another example, the tilted magnetic field trajectory is magnetic field trajectory 608 associated with a second reference angle. An example of a pinning direction for an MR element is pinning direction 602 (similar to the pinning direction on layer 222 (FIG. 2)).

[0029]

[0052] Referring to FIG. 6B, another example of graph 600 is graph 600′. Graph 600′ represents more than 200 gradient field trajectories. In graph 600′, an angle step of 1.5° is used to generate more than 200 gradient field trajectories, and a 2.5 Oe (199A / m) A field step of 0° is used. Each field trajectory represents a different reference angle. For example, field trajectory 612 is associated with a reference angle of 135°, and field trajectory 614 is associated with a reference angle of 0°.

[0030]

[0053] Referring to FIG. 7, a graph 700 shows each line (eg, line 702, line 704) indicating the resistance of an MR element relative to a reference 602, for example, for a linear locus 612.

[0031]

[0054] 8, graph 800 is identical to graph 300, except that linear trajectories 802 and 804 include locations 806 and 808, respectively. Locations 806 and 808 indicate where in the horizontal magnetic field (Hx) it is desirable for the linear bridge to produce a zero voltage output.

[0032]

[0055] 9, an example of a linear bridge that is linear but has an output that includes a point where the output voltage is zero is bridge 902. Bridge 902 is similar to bridge 402, but includes a third type of MR element. A reference angle for the third type of MR element is determined to allow the horizontal magnetic field strength (Hx) value at a desired position (e.g., either position 806 or position 808) to be the point where bridge 902 has zero output.

[0033]

[0056] Bridge 902 includes MR element 904a, MR element 904b, MR element 906a, MR element 906b, MR element 908a, and MR element 908b. Each of MR elements 904a, 904b, 906a, 906b, 908a, and 908b has a reference direction. For example, MR element 904a has reference direction 914a, MR element 904b has reference direction 914b, MR element 906a has reference direction 916a, MR element 906b has reference direction 916b, MR element 908a has reference direction 918a, and MR element 908b has reference direction 918b.

[0034]

[0057] The MR element 904a and the MR element 904b are of a first type, ie, the MR elements 904a, 904b are electrically identical and their reference angles 914a, 914b are equal.

[0035]

[0058] The MR element 906a and the MR element 906b are of a second type, ie, the MR elements 906a, 906b are electrically identical and their reference angles 916a, 916b are equal.

[0036]

[0059] The MR elements 908a and 908b are of a second type, ie, the MR elements 908a, 908b are electrically identical and their reference angles 918a, 918b are equal.

[0037]

[0060] 10, graph 1000 includes curve 1002, which is an example curve of the voltage output of a bridge, such as bridge 902 (FIG. 9). Curve 1002 is substantially linear, indicating that the bridge output has a linear response to a horizontal magnetic field.

[0038]

[0061] 11, a process for determining the reference angle for a third type of MR element is process 1100. Process 1000 determines 1102 the resistor with the smallest ratio of dynamic resistance to average resistance (over the entire trajectory of the applied magnetic field). For example, in graph 700, when the dynamic resistance varies with the applied magnetic field, the resistor with the smallest ratio of dynamic resistance to average resistance is determined.

[0039]

[0062] The process 1100 selects 1106 the reference angle associated with the resistor combination having the smallest ratio of dynamic resistance to average resistance (across the entire trajectory of the applied magnetic field). For example, in graph 700, the reference angle associated with the resistor having the smallest ratio of dynamic resistance to average resistance is selected.

[0040]

[0063] In another example, instead of adding MR 908a, 908b elements, a combination of multiple MR elements with different reference directions may be added, which when connected together in series or parallel may produce a small dynamic resistance to average resistance ratio.

[0041]

[0064] 12, an example computer is computer 1200 that includes a processor 1202, volatile memory 1204, non-volatile memory 1206 (e.g., a hard disk), and a user interface (UI) 1208 (e.g., a graphical user interface, a mouse, a keyboard, a display, a touch screen, etc.). The non-volatile memory 1206 stores computer instructions 1212, an operating system 1216, and data 1218. In one example, the computer instructions 1212 are executed by the processor 1202 from the volatile memory 1204 to perform all or a portion of the processes described herein (e.g., processes 500 and 1100).

[0042]

[0065] The processes described herein (e.g., processes 500 and 1100) are not limited to use with the hardware and software of FIG. 12; they may find applicability in any computing or processing environment and on any type of machine or set of machines capable of running a computer program. The processes described herein may be implemented in hardware, software, or a combination of the two. The processes described herein may be implemented in a computer program running on a programmable computer / machine, each of which includes a processor, a non-transitory machine-readable medium or other article readable by the processor (including volatile and non-volatile memory and / or storage elements), at least one input device, and one or more output devices. Program code may be applied to data entered using the input device to perform any of the processes described herein and to generate output information.

[0043]

[0066] The system may be implemented, at least in part, by a computer program product (e.g., in a non-transitory machine-readable storage medium) for execution by or to control the operation of a data processing device (e.g., a programmable processor, computer, or multiple computers). Each such program may be implemented in a high-level procedural or object-oriented programming language to communicate with a computer system. However, the program may also be implemented in assembly or machine language. The language may be a compiled or interpreted language, and the language may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program may be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communications network. A computer program may be stored and executed on a non-transitory machine-readable medium that is readable by a general-purpose or special-purpose programmable computer, and when read by the computer, the non-transitory machine-readable medium configures and operates the computer to perform the processes described herein. For example, the processes described herein may also be implemented as a non-transitory machine-readable storage medium configured by a computer program, where, when executed, the instructions in the computer program cause the computer to operate according to the process. Non-transitory machine-readable media may include, but are not limited to, hard drives, compact disks, flash memory, non-volatile memory, volatile memory, magnetic diskettes, etc., and are essentially free of transitory signals.

[0044]

[0067] The processes described herein are not limited to the particular examples described. For example, processes 500 and 1100 are not limited to the particular processing orders of Figures 5 and 11, respectively. Rather, any of the processing blocks of Figures 5 and 11 can be reordered, combined, or eliminated, and performed in parallel or sequentially, as necessary, to achieve the results described above.

[0045]

[0068] The processing blocks associated with implementing the system (e.g., processes 500 and 1100) may be performed by one or more programmable processors executing one or more computer programs to perform the functions of the system. All or portions of the system may be implemented as special-purpose logic circuitry (e.g., FPGAs (field-programmable gate arrays) and / or ASICs (application-specific integrated circuits)). All or portions of the system may be implemented using electronic hardware circuitry including, for example, electronic devices such as a processor, memory, programmable logic devices, or at least one of logic gates.

[0046]

[0069] 13, some applications require a linear bridge that is sensitive to magnetic field strength in the absence of an external magnetic field bias. For example, graph 1300 represents a magnetic field locus 1302 that it is desired that the linear bridge be able to detect. In this example, magnetic field locus 1302 has a non-zero horizontal magnetic field strength value and a zero vertical magnetic field strength value. In particular, the non-zero horizontal magnetic field strength value of magnetic field locus 1302 is 200 Oe. (15915A / m) is greater than.

[0047]

[0070] 14, typically, GMR and TMR elements do not function at high magnetic fields because it exceeds their linear range and their saturation region. For example, as shown in graph 1400, the resistance curve 1402 of a TMR element exhibits a resistance of 500 Oe for a TMR element with its reference direction aligned along the horizontal magnetic field axis. (39789A / m)The drop in resistance is caused by spin flop, which is a breakdown of the reference layer orientation.

[0048]

[0071] 15, spin flop can produce different curves depending on the orientation of the reference layer. For example, graph 1500 shows curve 1502 for a TMR element oriented perpendicular to the horizontal magnetic field axis. (11937A / m) to 800 Oe (63662A / m) The TMR element exhibits linear behavior during . Thus, an MR bridge of TMR or GMR elements can be configured for sensors that use an unconventional reference direction (i.e., perpendicular to the sensitive direction of the sensor) to achieve a linear sensor that can operate with magnetic field strengths significantly higher than the upper limit of the linear and saturation range of the GMR or TMR element alone.

[0049]

[0072] Referring to Figure 16, 200 Oe (15915A / m) An example of a linear bridge that operates in a larger magnetic field is linear bridge 1602. In one example, linear bridge 1602 is a current-driven bridge. Linear bridge 1602 is configured to detect changes in magnetic field strength in direction 1650, which is the sensitive direction of linear bridge 1602. In one example, bridge 1602 can detect a magnetic field trajectory, such as magnetic field trajectory 1302 (FIG. 13).

[0050]

[0073] Bridge 1602 includes MR element 1604a, MR element 1604b, MR element 1606a, and MR element 1606b. Each of MR elements 1604a, 1604b, 1606a, and 1606b has a reference direction. For example, MR element 1604a has reference direction 1614a, MR element 1604b has reference direction 1614b, MR element 1606a has reference direction 1616a, and MR element 1606b has reference direction 1616b.

[0051]

[0074] The MR element 1604a and the MR element 1604b are coupled to a MR transducer 1606 along a direction 1650 (e.g., 200 Oe (15915A / m)For high magnetic field strengths (greater than 1000 MHz), the type of MR element used, i.e., the type of sensitive MR element, is more sensitive to changes in magnetic field strength. For example, MR elements 1604a and 1604b are more sensitive to changes in magnetic field strength in linear bridge 1602 compared to MR elements 1606a and 1606b. MR elements 1604a and 1604b are electrically identical, and their reference directions 1614a and 1614b are equal.

[0052]

[0075] In one example, the reference directions 1614a, 1614b are approximately perpendicular to the direction 1650. In one particular example, the reference directions 1614a, 1614b are offset from the direction 1650 by between 80° and 130°. In another particular example, the reference directions 1614a, 1614b are offset from the direction 1650 by between −80° and −130°.

[0053]

[0076] MR elements 1606a and 1606b are types of MR elements used to compensate for the nonlinearity of other MR elements, i.e., compensation MR elements. For example, MR elements 1606a and 1606b are used to compensate for the nonlinearity of MR elements 1604a and 1604b. In one particular example, the number of pillars for MR elements 1606a and 1606b is selected to define a controlled offset of the bridge output at a desired magnetic field strength value. Compared to MR elements 1604a and 1604b, MR elements 1606a and 1606b provide almost no sensitivity to changes in magnetic field strength in linear bridge 1602.

[0054]

[0077] The MR elements 1606a, 1606b are electrically identical and their reference directions 1616a, 1616b are equal. In one example, the reference directions 1616a, 1616b are approximately parallel to the direction 1650. In one particular example, the reference directions 1616a, 1616b are offset from the direction 1650 by between −20° and 20°.

[0055]

[0078] Referring to Figure 17, graph 1700 depicts curve 1702, an example of the output signal of linear bridge 1602 (Figure 16). Curve 1702 represents a signal at approximately 350 Oe (27852A / m) (e.g., about 300 Oe (23873A / m) to approximately 650 Oe (51725A / m) The linear range of the linear bridge is set to 0 mV at approximately 470 Oe (37401 A / m). Curve 1702 has a 0.7% integral nonlinearity (INL) and a sensitivity of approximately 0.18 mV / Oe for a power consumption of 250 microwatts. (2.26e-6Vm / A) is.

[0056]

[0079] Referring to Figures 18A and 18B, 200 Oe (15915A / m) Another example of a linear bridge that operates at greater magnetic field strengths is linear bridge 1802. Bridge 1802 is similar to bridge 1602 (FIG. 16), except that the MR elements that compensate for nonlinearity (MR elements 1606a and 1606b in FIG. 16) are each replaced by two MR elements as described herein. In one example, linear bridge 1802 is a current-driven bridge.

[0057]

[0080] As will be described further herein, bridge 1802 can be configured to have a temperature-independent linear output for a defined temperature range (e.g., −10° C. to 100° C.). As will be described further herein, the selection of the number of pillars for each of MR elements 1804a, 1804b, 1806a, 1806b, 1808a, 1808b and the selection of reference directions 1814a, 1814b, 1816a, 1816b, 1818a, 1818b can be used to compensate for temperature. For example, the number of pillars and the precise reference directions 1814a, 1814b, 1816a, 1816b, 1818a, 1818b of each element 1804a, 1804b, 1806a, 1806b, 1808a, 1808b are selected to define the controlled offset to zero at the desired magnetic field strength value while not exceeding the maximum resistance of the bridge 1802 over temperature and to reduce the temperature dependence of the controlled offset and sensitivity as much as possible.

[0058]

[0081] Linear bridge 1802 is configured to detect magnetic field strength changes in direction 1850, which is the sensitive direction of linear bridge 1802, to detect magnetic field strength changes in magnetic field trajectories, such as magnetic field trajectory 1842. Similar to magnetic field trajectory 1302 (FIG. 13), magnetic field trajectory 1842 has a non-zero horizontal magnetic field strength value and a zero vertical magnetic field strength value. In particular, the non-zero horizontal magnetic field strength value of magnetic field trajectory 1842 is 200 Oe. (15915A / m) is greater than.

[0059]

[0082] Bridge 1802 includes MR element 1804a, MR element 1804b, MR element 1806a, MR element 1806b, MR element 1808a, and MR element 1808b. MR element 1804a has a reference direction 1814a, MR element 1804b has a reference direction 1814b, MR element 1806a has a reference direction 1816a, MR element 1806b has a reference direction 1816b, MR element 1808a has a reference direction 1818a, and MR element 1808b has a reference direction 1818b.

[0060]

[0083] MR elements 1804a and 1804b are sensitive MR elements similar to MR elements 1604a and 1604b (FIG. 16). MR elements 1804a and 1804b are electrically identical, and their reference directions 1814a and 1814b are equal.

[0061]

[0084] In one example, the reference directions 1814a, 1814b are perpendicular to the sensitive direction 1850 of the linear sensor 1802. In one particular example, the reference directions 1814a, 1814b are offset from the direction 1850 by between 80° and 130°. In another particular example, the reference directions 1814a, 1814b are offset from the direction 1850 by between −80° and −130°.

[0062]

[0085] MR elements 1806a, 1806b and MR elements 1808a, 1808b are compensation MR elements similar to MR elements 1606a, 1606b (FIG. 16) and are used to compensate for the nonlinearity of MR elements 1804a, 1804b. MR elements 1806a, 1806b are electrically identical, and their reference angles 1816a, 1816b are equal. MR elements 1808a, 1808b are electrically identical, and their reference angles 1818a, 1818b are equal.

[0063]

[0086] Compared to MR elements 1804a and 1804b, MR elements 1806a, 1806b, 1808a, and 1808b provide almost no sensitivity in linear bridge 1802. MR elements 1806a, 1806b, 1808a, and 1808b are used to compensate for the nonlinearity of MR elements 1804a and 1804b. In one particular example, the number of pillars for MR elements 1806a, 1806b, 1808a, and 1808b is selected to offset the nonlinearity of MR elements 1804a and 1806b.

[0064]

[0087] In one example, the reference directions 1816a, 1816b are approximately anti-parallel to the direction 1850. In one particular example, the reference directions 1816a, 1816b are offset from the direction 1850 by between 160° and 200°. In one particular example, the reference directions 1816a, 1816b are selected such that the resistances of the MR elements 1806a, 1806b are at their maximum resistances.

[0065]

[0088] In one example, reference directions 1818a, 1818b are approximately parallel to direction 1850. In one particular example, reference directions 1816a, 1816b are offset from direction 1850 by between −20° and 20°. In one particular example, reference directions 1818a, 1818b are selected such that the resistances of MR elements 1808a, 1808b are at their minimum resistances.

[0066]

[0089] In one particular example, the number of pillars for MR elements 1806a, 1806b and MR elements 1808a, 1808b is selected so that the combined temperature coefficient of MR elements 1806a, 1806b and MR elements 1808a, 1808b is relatively close to the temperature coefficient of MR elements 1804a, 1804b. In one example, the number of pillars for each of MR elements 1804a, 1804b, 1806a, 1806b, 1808a, 1808b is selected along with a reference direction in an optimization process.

[0067]

[0090] Referring to FIG. 19A, a graph 1900 shows the resistance R of the MR elements 1804a, 1804b at several different temperatures. A For example, curve 1902 shows the resistance R at a temperature of -9.5°C. A For example, curve 1904 shows the resistance R at a temperature of 27.5°C. A For example, curve 1906 shows the resistance R at a temperature of 59.0°C. A For example, curve 1908 shows the resistance R at a temperature of 69.7°C. AFor example, curve 1910 shows the resistance R at a temperature of 90.7°C. A It represents the horizontal magnetic field strength.

[0068]

[0091] Referring to FIG. 19B, a graph 1940 shows the resistance R of the MR elements 1806a, 1806b at several different temperatures. B For example, curve 1942 shows the resistance R at a temperature of -9.5°C. B For example, curve 1944 shows the resistance R at a temperature of 27.5°C. B For example, curve 1946 shows the resistance R at a temperature of 59.0°C. B For example, curve 1948 shows the resistance R at a temperature of 69.7°C. B For example, curve 1950 shows the resistance R at a temperature of 90.7°C. B It represents the horizontal magnetic field strength.

[0069]

[0092] Referring to FIG. 19C, a graph 1960 shows the resistance R of the MR elements 1808a, 1808b at several different temperatures. C For example, curve 1952 shows the resistance R at a temperature of -9.5°C. C For example, curve 1954 shows the resistance R at a temperature of 27.5°C. C For example, curve 1956 shows the resistance R at a temperature of 59.0°C. C For example, curve 1958 shows the resistance R at a temperature of 69.7°C. C For example, curve 1960 shows the resistance R at a temperature of 90.7°C. C It represents the horizontal magnetic field strength.

[0070]

[0093] Referring to FIG. 20, a graph 2000 shows the temperature distribution of the various different temperatures used in FIGS. 19A-19C. By degree20 represents the output of a linear bridge (e.g., linear bridge 1802 (FIG. 18A)) versus horizontal magnetic field strength values. As shown in FIG. 20, the selection of the number of pillars and reference directions 1814a, 1814b, 1816a, 1816b, 1818a, 1818b for MR elements 1804a, 1804b, 1806a, 1806b, 1808a, 1808b allows the output of the linear bridge to be independent of temperature between −10° C. and 100° C.

[0071]

[0094] For example, curve 2002 represents bridge output versus horizontal magnetic field strength at a temperature of -9.5°C. For example, curve 2004 represents bridge output versus horizontal magnetic field strength at a temperature of 27.5°C. For example, curve 2006 represents bridge output versus horizontal magnetic field strength at a temperature of 59.0°C. For example, curve 2008 represents bridge output versus horizontal magnetic field strength at a temperature of 69.7°C. For example, curve 2010 represents bridge output versus horizontal magnetic field strength at a temperature of 90.7°C.

[0072]

[0095] 21, a table 2100 shows the number of pillars and reference angles selected for MR elements 1804a, 1804b, 1806a, 1806a, 1808a, and 1808a to obtain the linear curves 2002, 2004, 2006, 2008, and 2010 in FIG. 20. For example, MR elements 1804a and 1804b each have a number of pillars of 17.5, and reference angles 1814a and 1814b are each −112.75°, MR elements 1806a and 1806b each have a number of pillars of 6, and reference angles 1816a and 1816b are each 175°, and MR elements 1808a and 1808b each have a number of pillars of 12.5, and reference angles 1818a and 1816b are −8°.

[0073]

[0096] 22, the linear bridges described herein (e.g., bridge 402, bridge 1002, bridge 1602, bridge 1802) may be used in a camera. In one example, the camera may be used in a mobile phone. Camera 2200 includes a magnetic field sensor 2204, a focus control 2224, a lens 2236, and a magnetic target 2236.

[0074]

[0097] The magnetic field sensor 2204 includes a bridge 2212. In one example, the bridge 2212 is similar to the bridge 402. In another example, the bridge 2212 is similar to the bridge 1002. In a further example, the bridge 2212 is similar to the bridge 1602. In yet a further example, the bridge 2212 is similar to the bridge 1902.

[0075]

[0098] In one example, the magnetic target 2236 can be moved and detected by the magnetic field sensor 2204 to provide an output to the focus controller 2224 to change the focal length of the lens 2236 .

[0076]

[0099] Elements of different embodiments described herein may be combined to form other embodiments not specifically discussed above. Various elements that are described in the context of a single embodiment may also be provided separately or in any suitable subcombination. Other embodiments not specifically described herein are also within the scope of the appended claims.

Claims

1. A bridge, a first magnetoresistive element having a first reference direction; a second magnetoresistive element in series with the first magnetoresistive element and having a second reference direction; a third magnetoresistive element in parallel with the first magnetoresistive element and having the first reference direction; a fourth magnetoresistive element in series with the third magnetoresistive element and having the second reference direction; Equipped with the first magnetoresistive element and the third magnetoresistive element are first-type magnetoresistive elements, the second magnetoresistive element and the fourth magnetoresistive element are second-type magnetoresistive elements, the first reference direction indicates a direction in which the first type magnetoresistive element is most sensitive to changes in a magnetic field; the second reference direction indicates a direction in which the second type magnetoresistive element is most sensitive to changes in a magnetic field; the first reference direction and the second reference direction are set so that the output of the bridge has a linear response over a range of horizontal magnetic field strength values ​​of at least 200 Oe (15915 A / m) to 600 Oe (47746 A / m); bridge.

2. 2. The bridge of claim 1, wherein the first, second, third, and fourth magnetoresistive elements are each giant magnetoresistive (GMR) elements or tunneling magnetoresistive (TMR) elements.

3. a fifth magnetoresistive element in series with the first magnetoresistive element and having a third reference direction; 2. The bridge of claim 1, further comprising a sixth magnetoresistive element in series with said third magnetoresistive element and having said third reference direction.

4. The bridge of claim 3 , wherein the fifth magnetoresistive element and the sixth magnetoresistive element are configured with the same number of pillars.

5. The bridge of claim 1 , wherein the first magnetoresistive element and the third magnetoresistive element are configured with the same number of pillars.

6. The bridge of claim 1 , wherein the second magnetoresistive element and the fourth magnetoresistive element are configured with the same number of pillars.

7. The linear response is greater than 300 Oe (23873 A / m) and less than 600 Oe (4774 10. The bridge of claim 1, wherein the horizontal magnetic field ranges from 0.5 to 1.0 A / m. Ji.

8. The bridge of claim 1 , wherein the bridge has the linear response over a temperature range of −10° C. to 100° C.

9. The bridge of claim 1 , wherein the first reference direction is substantially perpendicular to the second reference direction and to a magnetic field sensed by a magnetic field sensor including the bridge.

10. 1. A camera with a magnetic field sensor including a bridge, The bridge is a first magnetoresistive element having a first reference direction; a second magnetoresistive element in series with the first magnetoresistive element and having a second reference direction; a third magnetoresistive element in parallel with the first magnetoresistive element and having the first reference direction; a fourth magnetoresistive element in series with the third magnetoresistive element and having the second reference direction; the first magnetoresistive element and the third magnetoresistive element are first-type magnetoresistive elements, the second magnetoresistive element and the fourth magnetoresistive element are second-type magnetoresistive elements, the first reference direction indicates a direction in which the first type magnetoresistive element is most sensitive to changes in a magnetic field; the second reference direction indicates a direction in which the second type magnetoresistive element is most sensitive to changes in a magnetic field; the first reference direction and the second reference direction are set so that the output of the bridge has a linear response over a range of horizontal magnetic field strength values ​​of at least 200 Oe (15915 A / m) to 600 Oe (47746 A / m); further comprising a magnetic target, a focus controller, and a lens; The camera, wherein movement of the magnetic target is detected by the magnetic field sensor to provide an output to the focus controller to change the focal length of the lens.

11. A cellular device comprising the camera described in claim 10.

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