Magnetic field sensors are used in a variety of applications, including, but not limited to, an angle sensor that senses an angle of a direction of a magnetic field; a current sensor that senses a magnetic field generated by a current carried by a current-carrying conductor; a magnetic switch that senses the proximity of a ferromagnetic object; a rotation detector that senses passing ferromagnetic articles, for example, magnetic domains of a ring magnet or a ferromagnetic target (e.g., gear teeth) where the magnetic field sensor is used in combination with a back-biased or other magnet; a magnetic field sensor that senses a magnetic field density of a magnetic field, a linear sensor that senses a position of a ferromagnetic target; and so forth.
A magnetic field sensor may include a magnetic field sensing element. The magnetic field sensing element is used to describe a variety of electronic elements that can sense a magnetic field. The magnetic field sensing element can be, but is not limited to, a Hall effect element, a magnetoresistance element, or a magnetotransistor. As is known, there are different types of Hall effect elements, for example, a planar Hall element, a vertical Hall element, and a Circular Vertical Hall (CVH) element. There are different types of magnetoresistance elements, for example, a semiconductor magnetoresistance element such as Indium Antimonide (InSb), a giant magnetoresistance (GMR) element, for example, a spin valve, an anisotropic magnetoresistance element (AMR), a tunneling magnetoresistance (TMR) element, and a magnetic tunnel junction (MTJ). The magnetic field sensing element may be a single element or, alternatively, may include two or more magnetic field sensing elements arranged in various configurations, e.g., a half bridge or full (Wheatstone) bridge. Depending on the device type and other application requirements, the magnetic field sensing element may be a device made of a type IV semiconductor material such as Silicon (Si) or Germanium (Ge), or a type III-V semiconductor material like Gallium-Arsenide (GaAs) or an Indium compound, e.g., Indium-Antimonide (InSb).
According to aspects of the disclosure, a magnetic field current sensor is provided comprising: a conductor including a first turn, a second turn, and a third turn; planar Hall elements including: (i) a first planar Hall element generating a first signal, the first planar Hall element being disposed directly above or below a first region that is partially enclosed by the first turn, (ii) a second planar Hall element generating a second signal, the second planar Hall element being disposed directly above or below a second region that is partially enclosed by the second turn, (iii) a third planar Hall element generating a third signal, the third planar Hall element being disposed directly above or below the second region that is partially enclosed by the second turn, and (iv) a fourth planar Hall element generating a fourth signal, the fourth planar Hall element being disposed directly above or below a third region that is partially enclosed by the third turn; and circuitry that generates a difference signal indicative of twice the second signal less the first signal and less the fourth signal, wherein the second planar Hall element is interleaved with the third planar Hall element, wherein the second signal and the third signal are substantially equal, wherein the first planar Hall element, the second planar Hall element, the third planar Hall element and the fourth planar Hall element are in a first plane, and wherein a distance between the first planar Hall element and the second planar Hall element is equal to a distance between the second planar Hall element and the fourth planar Hall element.
According to aspects of the disclosure, a magnetic field current sensor is provided comprising: a two-turn conductor including a first turn and a second turn, vertical Hall elements including: (i) a first vertical Hall element generating a first signal, the first vertical Hall element being disposed directly above or below a first portion of the conductor that is part of the first turn only, (ii) a second vertical Hall element generating a second signal, the second vertical Hall element being disposed directly above or below a second portion of the conductor that is part of both the first turn and the second turn, (iii) a third vertical Hall element generating a third signal, the third vertical Hall element being disposed directly above or below the second portion of the conductor, and (iv) a fourth vertical Hall element generating a fourth signal, the fourth vertical Hall element being disposed directly above or below a fourth portion of the conductor that is part of the second turn only; and circuitry that generates a difference signal indicative of twice the second signal less the first signal and less the fourth signal, wherein the second vertical Hall element is interleaved with the third vertical Hall element, wherein the second signal and the third signal are substantially equal, wherein the first vertical Hall element, the second vertical Hall element, the third vertical Hall element and the fourth vertical Hall element are in a first plane, and wherein a distance between the first vertical Hall element and the second vertical Hall element is equal to a distance between the second vertical Hall element and the fourth vertical Hall element.
According to aspects of the disclosure, a magnetic field current sensor is provided comprising: a conductor; magnetic field sensing elements including a first magnetic field sensing element generating a first signal, a second magnetic field sensing element generating a second signal, a third magnetic field sensing element generating a third signal, and a fourth magnetic field sensing element generating a fourth signal; circuitry that generates a difference signal indicative of twice the second signal less the first signal and less the fourth signal, wherein the second magnetic field sensing element is interleaved with the third magnetic field sensing element, wherein the second signal and the third signal are substantially equal, and wherein a distance between the first magnetic field sensing element and the second magnetic field sensing element is equal to a distance between the second magnetic field sensing element and the fourth magnetic field sensing element.
The foregoing features may be more fully understood from the following description of the drawings. The drawings aid in explaining and understanding the disclosed technology. Since it is often impractical or impossible to illustrate and describe every possible embodiment, the provided figures depict one or more illustrative embodiments. Accordingly, the figures are not intended to limit the scope of the broad concepts, systems and techniques described herein. Like numbers in the figures denote like elements.
Described herein are techniques to fabricate a current sensor that reduces the impact of stray magnetic fields. In one example, a current sensor includes an annihilation detector circuit and includes magnetoresistance elements that have a magnetic vortex in a free layer. In another example, a current sensor includes magnetoresistance elements that have at least two different pillar diameters and have a magnetic vortex in a free layer. In a further example, a current sensor includes magnetoresistance elements that have a magnetic vortex in a free layer and have some magnetoresistance elements that have reference directions that are 180° from other magnetoresistance elements. In a still further example, magnetic field sensing elements such as a planar Hall element, vertical Hall elements and magnetoresistance elements may be used in certain configurations in a current sensor to reduce gradient stray magnetic field effects and common mode stray magnetic field effects.
Referring to
A free layer 130 includes the CoFeB layer 128. In some examples, the free layer 130 may include an additional layer of nickel iron (NiFe) (not shown) and a thin layer of tantalum (not shown) between the CoFeB layer 128 and the NiFe layer.
Referring to
The magnetic vortex has a core 170 (sometimes called a “magnetic vortex core”). Closer to the center of the core 170, the magnetization directions start to become more and more non-planar the closer to the center of the core 170. That is, the angle of the magnetization direction with respect to the surface of the free layer 160 increases the closer to the center of the core 170 a magnetization direction is. For example, an angle of the magnetization direction 164b with respect to the surface of the free layer 160 is higher than the angle of the magnetization direction 164a with respect to the surface of the free layer 160, an angle of the magnetization direction 164c with respect to the surface of the free layer 160 is higher than the angle of the magnetization direction 164b with respect to the surface of the free layer 160, and an angle of the magnetization direction 164d with respect to the surface of the free layer 160 is higher than the angle of the magnetization direction 164c with respect to the surface of the free layer 160.
Exchange energy and demagnetizing energy are two key phenomena in magnetic disks. Exchange energy increases energy cost when the magnetization is not homogeneous across the magnetic material of the magnetic disk while the demagnetizing energy increases cost when the magnetization directions point outside of the magnetic disk. Exchange energy is a volume effect term while demagnetizing energy is an edge effect term.
Referring to
Referring back to
Referring to
Referring to
Referring to
However, between HAN1 and HN1 and between HN2 and HAN2, the TMR signal response 202 may be either linear or saturated. For example, the TMR signal response 202 between HN2 and HAN2 is linear along a portion 214a and saturated along the portion 218a, and the TMR signal response 202 between HN1 and HAN1 is linear along a portion 214b and saturated along the portion 218b.
Saturation occurs when a magnetic vortex of TMR is exposed to a magnetic field that is higher than HAN1 Or HAN2 (i.e., the vortex is annihilated) and the TMR signal response 202 does not return to HN1 or HN2, respectively. An annihilation detector as described herein (e.g., an annihilation detector 300 (
A point 252a on the TMR signal 202 response corresponds to the free layer 160 in
Referring to
An output of the annihilation bridge 302 is trimmed by the offset trim circuit 306a and then rectified by the rectifier 310a. The comparator 314a compares the rectified signal from the rectifier 310a with a first threshold value. In one example, if the rectified signal from the rectifier 310a is higher than the first threshold, then the vortex is annihilated. In one example, the first threshold is derived from a hysteresis curve.
An output of the current bridge 324 is trimmed by the offset trim circuit 306b and then rectified by the rectifier 310b. The comparator 314b compares the rectified signal from the rectifier 310b with a second threshold value. In one example, if the rectified signal from the rectifier 310b is higher than the second threshold, then the vortex is annihilated. In one example, the second threshold may be the current that corresponds to HAN1 and/or HAN2.
The outputs of the comparator 314a, 314b are sent to the OR circuit 318. The OR circuit performs a logical “OR” function on the outputs of the comparator 314a, 314b to generate an output signal 350, which is an output for the annihilation detector 300.
Referring to
Referring to
TMR elements 502a, 502b, 502c, 502d each include a reference direction that is the same direction as the other TMR elements. A reference direction is the direction that the magnetoresistance element is most sensitive to changes in a magnetic field. For example, a resistance of the magnetoresistance element changes the most for changes in the magnetic field in the reference direction. The TMR element 502a has a reference direction 510a, the TMR element 502b has a reference direction 510b, the TMR element 502c has a reference direction 510c, and the TMR element 502d has a reference direction 510d.
The TMR elements 502a, 502b are on top of the conductor 506 and the TMR elements 502c, 502d are disposed between the TMR elements 502a, 502b and not in contact with the conductor 506. In one example, TMR element 502c and the TMR element 502d may be interleaved. In one example, the TMR elements 502a, 502b may be separated from the conductor 506 by a distance between 50 and 200 microns.
The TMR elements 502a, 502b, 502c, 502d are on a plane 512 that extends into and out of
Since the TMR elements 502c, 502d are placed in the center of the one-turn conductor 506, TMR elements 502c, 502d are exposed only to a stray magnetic field HSF, while the TMR elements 502a, 502b are exposed to both a stray magnetic field, HSF and the Oersted field caused by the current I (e.g., current 516) through the conductor 506. In one example, the TMR element 502a detects a magnetic field HA, the TMR element 502b detects a magnetic field HB, the TMR element 502c detects a magnetic field HC, and the TMR element 502d detects a magnetic field HD so that:
where a is a conversion factor from current to magnetic field.
Referring to
In one example, with a current source ICC1, the signal measured at node A and the signal measured at node B are each voltage signals. In another example, if the current source ICC1 is replaced with a fixed voltage source and the voltages are fixed at node A and node B, then the signal measured at node A and the signal measured at node B are each current signals.
The TMR element 502a and the TMR element 502c are electrically connected in series to form a first leg of the bridge 302′. The TMR element 502a is electrically closer to the current source ICC1 than the TMR element 502c.
The TMR element 502b and the TMR element 502d are electrically connected in series to form a second leg of the bridge 302′. The TMR element 502d is electrically closer to the current source ICC1 than the TMR element 502b.
By connecting the TMR elements 502a, 502b, 502c, 502d in a bridge one can obtain a net magnetic field due to stray field and the Oersted field of:
The signal is zero whatever the current or stray magnetic field are unless a vortex is annihilated because the magnetic field on one element is higher than HAN. Thus, the configuration in
Referring to
In one example, with a current source ICC2, the signal measured at node C and the signal measured at node D are each voltage signals. In another example, if the current source ICC2 is replaced with a fixed voltage source and the voltages are fixed at node C and node D, then the signal measured at node C and the signal measured at node D are each current signals.
The TMR element 502a and the TMR element 502b are electrically connected in series to form a first leg of the bridge 324′. The TMR element 502a is electrically closer in series to the current source ICC2 than the TMR element 502b.
The TMR element 502b and the TMR element 502a are electrically connected in series to form a second leg of the bridge 324′. The TMR element 502b is electrically closer in series to the current source ICC2 than the TMR element 502b.
Referring to
The TMR elements 602a, 602b are formed having pillars that have diameters that are smaller than pillars of TMR elements 604a, 604b. In one example, the TMR elements 602a, 602b are formed in pillars that have diameters of 2 microns, and the TMR elements 604a, 604b are formed in pillars that have diameters of 3 microns.
TMR elements 602a, 602b, 604a, 604b each include a reference direction that is the same direction as the other TMR elements. For example, the TMR element 602a has a reference direction 608a, the TMR element 602b has a reference direction 608b, the TMR element 604a has a reference direction 610a, and the TMR element 604b has a reference direction 610b.
The TMR elements 602a, 604a are on top of one end of the conductor 606 and the TMR elements disposed 602b, 604b are on top of the other end of the conductor 606. In one example, the TMR elements 602a, 602b, 604a, 604b may be separated from the conductor 606 by a distance between 50 and 200 microns.
The TMR elements 602a, 602b are on an axis 612a, and the TMR elements 604a, 604b are on an axis 612b. In one example, axis 612a is parallel to axis 612b. During operation, a current 616 is applied to one end of the conductor 606.
Referring to 6B, a bridge 614a includes TMR elements 602a, 602b. An output of the bridge 614a is the difference between a signal measured at node E and a signal measured at node F.
In one example, with a current source ICC3, the signal measured at node E and the signal measured at node F are each voltage signals. In another example, if the current source ICC3 is replaced with a fixed voltage source and the voltages are fixed at node E and node F, then the signal measured at node E and the signal measured at node F are each current signals.
The TMR element 602a and the TMR element 602b are electrically connected in series to form a first leg of the bridge 614a. The TMR element 602a is electrically closer in series to the current source ICC3 than the TMR element 602b.
The TMR element 602b and the TMR element 602a are electrically connected in series to form a second leg of the bridge 614a. The TMR element 602b is electrically closer in series to the current source ICC3 than the TMR element 602b.
A bridge 614b includes TMR elements 604a, 604b. An output of the bridge 614b is the difference between a signal measured at node G and a signal measured at node H.
In one example, with a current source ICC4, the signal measured at node G and the signal measured at node H are each voltage signals. In another example, if the current source ICC4 is replaced with a fixed voltage source and the voltages are fixed at node G and node H, then the signal measured at node G and the signal measured at node H are each current signals.
The TMR element 604a and the TMR element 604b are electrically connected in series to form a first leg of the bridge 614a. The TMR element 604a is electrically closer in series to the current source ICC4 than the TMR element 604b.
The TMR element 604b and the TMR element 604a are electrically connected in series to form a second leg of the bridge 614b. The TMR element 604b is electrically closer in series to the current source ICC4 than the TMR element 604b.
In one example, the bridge 614a and the bridge 614b are examples of current bridges each having different sensitivities to a magnetic field from one another and different inner ranges from one another. The bridge 614a has the largest linear range and is used as an example of the current bridge 324 (
Referring to
Referring to
TMR elements 702a, 704a, each include a reference direction that is the same direction. For example, the TMR element 702a has a reference direction 708a, the TMR element 704a has a reference direction 710a that are in the direction.
TMR elements 702b, 704b, each include a reference direction that is the same direction. For example, the TMR element 704a has a reference direction 708b, and the TMR element 704b has a reference direction 710b that are in the direction. The reference directions 708b, 710b are in a direction 180° different from the reference directions 708a, 710a.
The TMR elements 702a, 704b are on top of one end of the conductor 706 and the TMR elements disposed 702b, 704a are on top of the other end of the conductor 706. In one example, the TMR elements 702a, 702b, 704a, 704b may be separated from the conductor 706 by a distance between 50 and 200 microns.
In one example, the TMR element 702a and the TMR element 704b are separated by no less than 20 microns±5 microns. In one example, the TMR element 704a and the TMR element 702b are generally separated by 400 microns±100 microns. During operation, a current 716 is applied to one end of the conductor 706.
In one example, the TMR elements 702a, 704a may be on an axis 712a, and the TMR elements 702b, 704b may be on an axis 712b. In one example, the axis 712a is parallel to the axis 712b.
Referring to
In one example, with a current source ICC5, the signal measured at node I and the signal measured at node J are each voltage signals. In another example, if the current source ICC5 is replaced with a fixed voltage source and the voltages are fixed at node I and node J, then the signal measured at node I and the signal measured at node J are each current signals.
The TMR element 702a, 702b, 704a, 704b are electrically connected in series to form a first leg of the bridge 714. In one example, the TMR element 702a is electrically closer in series to the current source ICC5 than the TMR element 702b, the TMR element 702b is electrically closer in series to a current source ICC5 than the TMR element 704a, and the TMR element 704a is electrically closer in series to a current source ICC5 than the TMR element 704b.
The TMR element 704a, 704b, 702a, 702b are electrically connected in series to form a second leg of the bridge 714. In one example, the TMR element 704a is electrically closer in series to a current source ICC5 than the TMR element 704b, the TMR element 704b is electrically closer in series to a current source ICC5 than the TMR element 702a, and the TMR element 702a is electrically closer in series to a current source ICC5 than the TMR element 702b.
Referring to
TMR elements 802a, 802b, 802c, 802d each include a reference direction that is the same direction as the other TMR elements. For example, the TMR element 802a has a reference direction 810a, the TMR element 802b has a reference direction 810b, the TMR element 802c has a reference direction 810c, and the TMR element 802d has a reference direction 810d.
The TMR elements 802a, 802b, 802c, 802d are on top of the conductor 806. The TMR elements 802a, 802b, 802c, 802d are in the XY plane. During operation, a current 816 is applied to one end of the conductor 806. In one example, the TMR elements 802a, 802b, 802c, 802d may be separated from the conductor 606 by a distance between 50 and 200 microns.
The TMR element 802b is interleaved with the TMR element 802c. The distance between the TMR element 802a and the TMR element 802b is about the same as the distance between the TMR element 802b and the TMR 802d.
A bridge 814 includes TMR elements 802a, 802b, 802c, 802d. An output of the bridge 814 is the difference between a signal measured at node K and a signal measured at node L. In one example, the bridge 814 is an example of the current bridge 324 (
In one example, with a current source ICC6, the signal measured at node K and the signal measured at node L are each voltage signals. In another example, if the current source ICC6 is replaced with a fixed voltage source and the voltages are fixed at node K and node L, then the signal measured at node K and the signal measured at node L are each current signals.
The TMR element 802a and the TMR element 802b are electrically connected in series to form a first leg of the bridge 814. The TMR element 802a is electrically closer in series to the current source ICC6 than the TMR element 802b.
The TMR element 802c and the TMR element 802d are electrically connected in series to form a second leg of the bridge 814. The TMR element 802c is electrically closer in series to the current source ICC6 than the TMR element 802d.
Referring to
In one example, with a current source ICC22, the signal measured at node X and the signal measured at node Y are each voltage signals. In another example, if the current source ICC22 is replaced with a fixed voltage source and the voltages are fixed at node X and node Y, then the signal measured at node X and the signal measured at node Y are each current signals. The TMR element 802a and the TMR element 802c are electrically connected in series to form a first leg of the bridge 816. The TMR element 802a is electrically closer in series to the current source ICC22 than the TMR element 802c.
The TMR element 802c and the TMR element 802a are electrically connected in series to form a second leg of the bridge 816. The TMR element 802c is electrically closer in series to the current source ICC22 than the TMR element 802c.
In one example, the TMR element 802c may be replaced with the TMR element 802b in the bridge 816. In another example, the TMR element 802a may be replaced with the TMR element 802d in the bridge 816. In a further example, in the bridge 816, the TMR element 802c may be replaced with the TMR element 802b and the TMR element 802a may be replaced with the TMR element 802d.
In the current sensor configuration 800, common mode and gradient stray magnetic fields may be reduced along an X axis. Whatever the magnetic stray field distribution along the X axis, the magnetic stray field distribution can be decomposed in a Taylor series made of odd and even terms (where the TMR elements 802b, 802c are at X=0). In the following equations, only the common mode and the linear component are considered for simplicity. The signals coming from TMR elements 802a, 802b, 802c, 802d are, respectively, SigA, SigB, SigC, SigD, where:
and where:
An output of the bridge 814 or the difference of the current at the nodes I and J is:
By symmetry, the odd terms of the Taylor series are rejected, not just the linear gradient. Also, the differential bridge 816 rejects the even terms of the Taylor series of the stray field distribution (including common mode). So, depending on the stray field distribution symmetry, either the proposed construction or a simple differential field may be selected. In the case of current sensors, the stray magnetic field usually comes from adjacent current lines, so that the distribution of stray magnetic field is of the form 1/(x−x0) where x0 is the distance to the current line. In the current sensor configuration 800, most of the stray magnetic field is held in the common mode and linear gradient; so that the current sensor configuration 800 will reject a larger amount of the stray magnetic field.
Referring to
Referring to
The vertical Hall elements 1002a, 1002b, 1002c, 1002d each include a reference direction that is the same direction as the other vertical Hall elements. For example, the vertical Hall element 1002a has a reference direction 1010a, the vertical Hall element 1002b has a reference direction 1010b, the vertical Hall element 1002c has a reference direction 1010c, and the vertical Hall element 1002d has a reference direction 1010d.
The vertical Hall elements 1002a, 1002b, 1002c, 1002d are on top of the conductor 1006. The vertical Hall elements 1002a, 1002b, 1002c, 1002d are on a plane 1012 that extends into and out of
The vertical Hall element 1002b is placed side-by-side with the vertical Hall element 1002c. The distance between the TMR element 1002a and the vertical Hall element 1002b is about the same as the distance between the vertical Hall element 1002b and the vertical Hall element 1002d.
Referring to
The circuit 1020 includes a difference circuit 1026a, a difference circuit 1026b, and a difference circuit 1026c. The difference circuit 1026a takes the difference of signals SVHA and SVHB to produce an output signal equal to SVHA−SVHB. The difference circuit 1026b takes the difference of signals SVHC and SVHD to produce an output signal equal to SVHC−SVHD. The difference circuit 1026c takes the difference of signals SVHA−SVHB and SVHA−SVHB to produce an output signal 1050 equal to (SVHC−SVHD)−(SVHA−SVHB)=2SVHC−SVHA−SVHD.
Referring to
The planar Hall elements 1102a, 1102b, 1102c, 1102d are between the turns of the conductor 1106. The planar Hall elements 1102a, 1102b, 1102c, 1102d are on a plane 1112 that extends into and out of
The planar Hall element 1102b is placed side-by-side with the planar Hall element 1102c. The distance between the TMR element 1102a and the planar Hall element 1102b is about the same as the distance between the planar Hall element 1102b and the planar Hall element 1102d.
Referring to
The circuit 1120 includes a difference circuit 1126a, a difference circuit 1126b, and a difference circuit 1126c. The difference circuit 1126a takes the difference of signals SPHA and SPHB to produce an output signal equal to SPHA−SPHB. The difference circuit 1126b takes the difference of signals SPHC and SPHD to produce an output signal equal to SPHC−SPHD. The difference circuit 1126c takes the difference of signals SPHA−SPHB and SPHA−SPHB to produce an output signal 1150 equal to (SPHC−SPHD)−(SPHA−SPHB)=2SPHC−SPHA−SPHD.
Having described embodiments, which serve to illustrate various concepts, structures, and techniques, which are the subject of this patent, it will now become apparent to those of ordinary skill in the art that other embodiments incorporating these concepts, structures and techniques may be used.
Elements of different embodiments described herein may be combined to form other embodiments not specifically set forth above. Various elements, which 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 following claims.
This application is a divisional of and claims priority to U.S. patent application Ser. No. 17/806,336 filed on Jun. 10, 2022, the entire contents of which are hereby incorporated herein by reference.
Number | Date | Country | |
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Parent | 17806336 | Jun 2022 | US |
Child | 18893088 | US |