Magnetic field sensor for detecting an absolute position of a target object

A magnetic field sensor for sensing an absolute position of a target object can include one or more magnetic field sensing elements disposed proximate to a mechanical intersection of first and second portions of a target object, wherein the one or more magnetic field sensing elements are operable to generate a first magnetic field signal responsive to the movement of both the first and second portions. The magnetic field sensor can also include a position detection module operable to use the first magnetic field signal to generate a position value indicative of the absolute position. The magnetic field sensor can also include an output format module coupled to receive the position value and to generate an output signal from the magnetic field sensor indicative of the absolute position.

CROSS REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

FIELD OF THE INVENTION

This invention relates generally to magnetic field sensors, and, more particularly, to a magnetic field sensor that can detect an absolute position (e.g., a rotation absolute angle) of a target object.

BACKGROUND

Various types of magnetic field sensing elements are known, including Hall Effect elements and magnetoresistance elements. In contrast, magnetic field sensors generally include a magnetic field sensing element and other electronic components. Some magnetic field sensors also include a permanent magnet (a hard ferromagnetic object) in a so-called “back biased” arrangement described more fully below. With a back-biased arrangement, a moving ferromagnetic object can cause fluctuations in the magnetic field of the magnet, which is sensed by the back biased magnetic field sensor. Other magnetic field sensors can sense motion of a magnetic target object.

Magnetic field sensors provide an electrical signal representative of a sensed magnetic field. In some embodiments that have the magnet (back-biased arrangements), the sensed magnetic field is a magnetic field generated by the magnet, in which case, in the presence of a moving ferromagnetic object, the magnetic field generated by the magnet and sensed by the magnetic field sensor varies in accordance with a shape or profile of the moving ferromagnetic object. In contrast, magnetic field sensors that sense a moving magnet directly sense variations of magnetic field magnitude and direction that result from movement of the magnet.

Magnetic field sensors (back-biased) are often used to detect movement of features of a ferromagnetic gear, such as gear teeth and/or gear slots or valleys. A magnetic field sensor in this application is commonly referred to as a “gear tooth” sensor.

In some arrangements, the ferromagnetic gear is placed upon an object, for example, a camshaft in an engine or the shaft of an electric motor. Thus, it is the rotation of the object (e.g., camshaft) that is sensed by detecting the moving features of the ferromagnetic gear. Gear tooth sensors are used, for example, in automotive applications to provide information to an engine control processor for ignition timing control, fuel management, anti-lock braking systems, wheel speed sensors, electric motor commutation and other operations.

With regard to electric motors, information provided by the gear-tooth sensor to an electric motor control processor can include, but is not limited to, an absolute angle of rotation of an object (e.g. a motor shaft) as it rotates, a speed of the rotation, and a direction of the rotation. With this information the e-motor control processor can adjust the timing of commutating different magnetic coils of the motor.

However, in some electric motor drive applications, the gear tooth sensor does not provide accurate enough determination of angle of rotation, i.e., position, and direction of rotation of the electric motor shaft. One such application is for main drive electric motors used in electrical automobiles.

In some electric motor drive applications, a plurality of magnetic field sensing elements, e.g., three Hall elements, are used in relation to a plurality of windings of a multi-phase electric motor, which has a plurality of motor windings, in order to sense a position of the electric motor shaft. With this arrangement, an electric motor control processor can use signals from the plurality of magnetic field sensing elements to generate a plurality signals with proper phases communicated to the plurality of motor windings. However, in some electric motor drive applications, the plurality of magnetic field sensing elements also does not provide accurate enough determination of angle of rotation, i.e., position, and direction of rotation of the electric motor shaft.

Applications for which more accuracy is desired include, but are not limited to, main drive electric motors used in electrical automobiles.

Thus, it would be desirable to provide a magnetic field sensor that can identify, with improved accuracy, a rotational angle, i.e., a position, or a linear position of a target object as the target object moves. The target object can be coupled to, but is not limited to being coupled to, a shaft of an electric motor.

SUMMARY

The present invention provides a magnetic field sensor that can identify, with improved accuracy, a rotational angle, i.e., a position, or a linear position of a target object as the target object moves. The target object can be coupled to, but is not limited to being coupled to, a shaft of an electric motor.

In accordance with an example useful for understanding an aspect of the present invention, a magnetic field sensor for sensing an absolute position of a target object, wherein the target object has a first portion having a first quantity of target features and a second portion having a second quantity of target features different than the first quantity, wherein the first and second portions are proximate and mechanically fixed together, wherein the target object, including the first and second portions, is capable of a movement, the magnetic field sensor can include:

one or more magnetic field sensing elements disposed proximate to a mechanical intersection of the first and second portions of the target object, wherein the one or more magnetic field sensing elements are operable to generate a first magnetic field signal responsive to the movement of both the first and second portions;

a position detection module operable to use the first magnetic field signal to generate a position value indicative of the absolute position; and

an output format module coupled to receive the position value and to generate an output signal from the magnetic field sensor indicative of the absolute position.

In accordance with an example useful for understanding another aspect of the present invention, a method of sensing an absolute position of a target object, wherein the target object has a first portion having a first quantity of target features and a second portion having a second quantity of target features different than the first quantity, wherein the first and second portions are proximate and mechanically fixed together, wherein the target object, including the first and second portions, is capable of a movement, the method can include:

generating a first magnetic field signal responsive to the movement of both the first and second portions;

using the first magnetic field signal to generate a position value indicative of the absolute position; and

generating an output signal from the magnetic field sensor indicative of the absolute position.

In accordance with an example useful for understanding another aspect of the present invention, a magnetic field sensor for sensing an absolute position of a target object, wherein the target object has a first portion having a first quantity of target features and a second portion having a second quantity of target features different than the first quantity, wherein the first and second portions are proximate and mechanically fixed together, wherein the target object, including the first and second portions, is capable of a movement, the magnetic field sensor can include:

means for generating a first magnetic field signal responsive to the movement of both the first and second portions;

means for using the first magnetic field signal to generate a position value indicative of the absolute position; and

means for generating an output signal from the magnetic field sensor indicative of the absolute position.

DETAILED DESCRIPTION

Before describing the present invention, it should be noted that reference is sometimes made herein to target objects having a particular shape (e.g., round). One of ordinary skill in the art will appreciate, however, that the techniques described herein are applicable to a variety of sizes and shapes, including a flat target object.

Before describing the present invention, some introductory concepts and terminology are explained.

As is known, some of the above-described magnetic field sensing elements tend to have an axis of maximum sensitivity parallel to a substrate that supports the magnetic field sensing element, and others of the above-described magnetic field sensing elements tend to have an axis of maximum sensitivity perpendicular to a substrate that supports the magnetic field sensing element. In particular, planar Hall elements tend to have axes of sensitivity perpendicular to a substrate, while metal based or metallic magnetoresistance elements (e.g., GMR, TMR, AMR) and vertical Hall elements tend to have axes of sensitivity parallel to a substrate.

As used herein, the term “magnetic field sensor” is used to describe a circuit that uses a magnetic field sensing element, generally in combination with other circuits. 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, and a magnetic field sensor that senses a magnetic field density of a magnetic field.

The terms “parallel” and “perpendicular” are used in various contexts herein. It should be understood that the terms parallel and perpendicular do not require exact perpendicularity or exact parallelism, but instead it is intended that normal manufacturing tolerances apply, which tolerances depend upon the context in which the terms are used. In some instances, the term “substantially” is used to modify the terms “parallel” or “perpendicular.” In general, use of the term “substantially” reflects angles that are beyond manufacturing tolerances, for example, within +/−ten degrees.

As used herein, the term “processor” is used to describe an electronic circuit that performs a function, an operation, or a sequence of operations. The function, operation, or sequence of operations can be hard coded into the electronic circuit or soft coded by way of instructions held in a memory device. A “processor” can perform the function, operation, or sequence of operations using digital values or using analog signals.

In some embodiments, the “processor” can be embodied in an application specific integrated circuit (ASIC), which can be an analog ASIC or a digital ASIC. In some embodiments, the “processor” can be embodied in a microprocessor with associated program memory. In some embodiments, the “processor” can be embodied in a discrete electronic circuit, which can be analog or digital, and which may or may not have an arithmetic logic unit (ALU).

As used herein, the term “module” can be used to describe a “processor.” However, the term “module” is used more generally to describe any circuit that can transform an input signal into an output signal that is different than the input signal.

A processor can contain internal processors or internal modules that perform portions of the function, operation, or sequence of operations of the processor. Similarly, a module can contain internal processors or internal modules that perform portions of the function, operation, or sequence of operations of the module.

While electronic circuits shown in figures herein may be shown in the form of analog blocks or digital blocks, it will be understood that the analog blocks can be replaced by digital blocks that perform the same or similar functions and the digital blocks can be replaced by analog blocks that perform the same or similar functions. Analog-to-digital or digital-to-analog conversions may not be explicitly shown in the figures, but should be understood.

In particular, it should be understood that a so-called comparator can be comprised of an analog comparator having a two state output signal indicative of an input signal being above or below a threshold level (or indicative of one input signal being above or below another input signal). However, the comparator can also be comprised of a digital circuit having an output signal with at least two states indicative of an input signal being above or below a threshold level (or indicative of one input signal being above or below another input signal), respectively, or a digital value above or below a digital threshold value (or another digital value), respectively.

As used herein, the term “predetermined,” when referring to a value or signal, is used to refer to a value or signal that is set, or fixed, in the factory at the time of manufacture, or by external means, e.g., programming, thereafter. As used herein, the term “determined,” when referring to a value or signal, is used to refer to a value or signal that is identified by a circuit during operation, after manufacture.

As used herein, the term “amplifier” is used to describe a circuit element with a gain greater than one, less than one, or equal to one.

As used herein, the terms “line” and “linear” are used to describe either a straight line or a curved line. The line can be described by a function having any order less than infinite.

While planar Hall effect elements are shown in some figures herein, in other embodiments, any type of magnetic field sensing elements can be used.

The terms “absolute position” and “absolute angle” are used to refer to a position or an angle of a target object relative of a reference position determined by a position of a magnetic field sensor.

Referring toFIG. 1, a magnetic field sensor102can sense an absolute position (i.e., absolute rotation angle) of a target object106. The target object106has a first portion106ahaving a first quantity of target features, e.g., target features106aa,106ab, and a second portion106bhaving a second quantity of target features, e.g., target features106ba,106bb, different than the first quantity. The first and second portions106a,106bcan be mechanically fixed together. The target object106, including the first and second portions106a,106b, is capable of a movement relative to the magnetic field sensor102. The magnetic field sensor102can include a first one or more magnetic field sensing elements104adisposed proximate to the first portion106a. The first one or more magnetic field sensing elements104acan be operable to generate a first magnetic field signal responsive to the movement (e.g., rotation) of the first portion106a. The magnetic field sensor102can also include a second one or more magnetic field sensing elements104bdisposed proximate to the second portion106b. The second one or more magnetic field sensing elements104bcan be operable to generate a second magnetic field signal responsive to the movement of the second portion106b. The magnetic field sensor102can also include a position detection module coupled to use the first and second magnetic field signals to generate a position value indicative of the absolute position, and an output format module coupled to receive the position value and to generate an output signal from the magnetic field sensor indicative of the absolute position. The position detection module and the output format module are described in conjunction with figures below.

Examples described herein use target objects for which the quantities of features on the first and second portions of the target object differ by one feature. However, in other embodiments, the difference can be greater, for example, one, two, three, four, five, or more than five features.

Embodiments described herein use target objects having first and second target object portions that rotate or move in the same direction.

In some embodiments, some of the target features, e.g.,106aa,106ba, are teeth of a respective ferromagnetic gear portion and other target features, e.g.,106ab,106bb, are valleys. These embodiments can include a permanent magnet (see, e.g.,FIG. 10) disposed within or proximate to the magnetic field sensor102in a so-called “back-biased” arrangement. In a back-biased arrangement, the magnetic field sensor102experiences changes of magnetic field generated by the permanent magnet as the gear teeth and valleys pass by the magnetic field sensor102.

In other embodiments, some of the target features, e.g.,106aa,106baare north magnetic poles of a respective ring magnet portion and other target features, e.g.,106ab,106bb, are south magnetic poles. These embodiments have no back-biased magnet.

Referring now toFIG. 2, in which like element soFIG. 1are shown having like reference designations, the magnetic field sensor102is again shown proximate to the target object106. Here, the first one or more magnetic field sensing elements104acan include three magnetic field sensing elements S1, S2, S3, and the second one or more magnetic field sensing elements104bcan include three magnetic field sensing elements S4, S5, S6.

Electronic circuits that use the first one or more magnetic field sensing elements104aand the second one or more magnetic field sensing elements104bare shown in figures below.

Referring now toFIG. 3, a graph300has a horizontal axis with a scale in units of time in arbitrary units and a vertical axis with a scale in units of differential magnetic field in arbitrary units. In some embodiments, the differential field can be identified by a difference of signals from the magnetic field sensing elements S1, S2, S3ofFIG. 2and a difference of signals from the magnetic field sensing elements S4, S4, S6ofFIG. 2. In other embodiments described below, differential arrangements are not used and the magnetic field sensor can use only two of the magnetic field sensing elements S1, S2, or S3and S4, S5, or S6, taken individually.

A signal302is indicative of the difference of signals from the magnetic field sensing elements S1, S2, S3ofFIG. 2and a signal304is indicative of the difference of signals from the magnetic field sensing elements S4, S5, S6ofFIG. 2as the target object106spins or rotates. For example, referring briefly toFIGS. 1 and 2, signal302can be indicative of a difference S1-S2and signal304can be indicative of a difference S4-S5. However, other differences are possible.

Since the magnetic field sensing elements S1, S2, S3are proximate to the first portion106aof the target object106and the magnetic field sensing elements S4, S5, S6are proximate to the second portion106bof the target object106, the signals302,304can have a phase difference that changes with rotation of the target object.

The phase difference of the signals302,304can be determined in a variety of ways. In some embodiments, the phase difference can be determined using a threshold value306and comparing the first and second signal302,304to the threshold value306. Differences of times when the first signal302and the second signal304cross the threshold value306are identified as a shift(1) and a shift(2), each of which, in time (e.g., as a percentage of a period of one of the signals302,304), is indicative of a phase difference between the first and second signals302,304, wherein the phase difference changes with cycle of the first and second signals302,304. Period1 and Period2 are different periods.

The above arrangement is described more fully below in conjunction withFIGS. 4 and 5. Other arrangements that can identify the phase difference between the first and second signals302,304are described below in conjunction withFIGS. 6 and 7.

Referring now toFIG. 4, an illustrative magnetic field sensor400can be disposed proximate to a first portion404aof a target object and a second portion404bof a target object. The first and second portions404a,404bof the target object can be the same as or similar to the first and second portions106a,106bof the target object106ofFIGS. 1 and 2. While the first and second portions404a,404bshown to be separate, it should be understood that the first and second portions404a,404bare shown as being mechanically separate merely for clarity in reference to the magnetic field sensor400.

The magnetic field sensor400can include a first one or more magnetic field sensing elements406a,406b,406cdisposed proximate to the first portion404aof the target object. The magnetic field sensor400can also include a second one or more magnetic field sensing elements440a,440b,440cdisposed proximate to the second portion404bof the target object. The first one or more magnetic field sensing elements406a,406b,406ccan be the same as or similar to the first one or more magnetic field sensing elements104aofFIGS. 1 and 2. The second one or more magnetic field sensing elements440a,440b,440ccan be the same as or similar to the second one or more magnetic field sensing elements104bofFIGS. 1 and 2.

Magnetic field sensing elements406a,406ccan be coupled in a differential arrangement to input nodes of an amplifier408to generate an amplified signal408a.

An automatic gain control and automatic offset control circuit410can be coupled to the amplified signal408aand can generate a controlled signal410a, also indicated with a designation A.

A threshold generator circuit416can be coupled to the controlled signal410aand can generate a threshold signal416a.

The controlled signal410aand the threshold signal416acan be coupled to input nodes of comparator412to generate a comparison signal412a, also indicated with a designation A′. In some embodiments, the comparison signal412ais a two state signal with high states and low states. The comparison signal412acan also be referred to as a speed signal for which a rate of transitions is indicative of a speed of rotation of the first and second portions404a,404bof the target object.

Generation of threshold signals is briefly described above. Let it suffice here to say that the threshold generator416can be operable to identify one or more threshold values between a positive peak and a negative peak of the controlled signal410a. For example, in some embodiments, the threshold generator416can sequentially identify a first threshold value that is about sixty percent of a range between the positive peak and the negative peak of the controlled signal410a, and a second threshold value that is about forty percent of the range between the positive peak and the negative peak of the controlled signal410a. Thus, the comparison signal412acan have transitions of state when the controlled signal410acrosses upward past the first threshold value and crosses downward past the second threshold value, back and forth.

Magnetic field sensing elements406b,406ccan be coupled in another differential arrangement to input nodes of an amplifier422to generate an amplified signal422a.

The amplified signal408aand the amplified signal422acan both have characteristics comparable to the signal302ofFIG. 3.

An automatic gain control and automatic offset control circuit424can be coupled to the amplified signal422aand can generate a controlled signal424a, also indicated with a designation B.

A threshold generator circuit428can be coupled to the controlled signal424aand can generate a threshold signal428a.

The controlled signal424aand the threshold signal428acan be coupled to input nodes of a comparator426to generate a comparison signal426a, also indicated with a designation B′. In some embodiments, the comparison signal426ais a two state signal with high states and low states.

Magnetic field sensing elements440a,440ccan be coupled in a differential arrangement to input nodes of an amplifier442to generate an amplified signal442a. An automatic gain control and automatic offset control circuit446can be coupled to the amplified signal442aand can generate a controlled signal446a, also indicated with a designation C.

A threshold generator circuit450can be coupled to the controlled signal446aand can generate a threshold signal450a.

The controlled signal446aand the threshold signal450acan be coupled to input nodes of comparator448to generate a comparison signal448a, also indicated with a designation C′. In some embodiments, the comparison signal448ais a two state signal with high states and low states.

Magnetic field sensing elements440b,440ccan be coupled in another differential arrangement to input nodes of an amplifier452to generate an amplified signal452a.

The amplified signal442aand the amplified signal452acan both have characteristics comparable to the signal304ofFIG. 3, having a time/phase shift relative to the signals408a,422athat changes with rotation angle of the target object.

An automatic gain control and automatic offset control circuit454can be coupled to the amplified signal452aand can generate a controlled signal454a, also indicated with a designation D.

A threshold generator circuit458can be coupled to the controlled signal454aand can generate a threshold signal458a.

The controlled signal454aand the threshold signal458acan be coupled to input nodes of a comparator456to generate a comparison signal456a, also indicated with a designation D′. In some embodiments, the comparison signal456ais a two state signal with high states and low states.

The magnetic field sensor400can also include a position detection module428. The position detection module428can include a 4:2 multiplexer430coupled to the signals A and B (or alternatively, the signals A′ and B′). The 4:2 multiplexer430can also be coupled to the signals C and D (or alternatively, the signals C′ and D′).

The 4:2 multiplexer430is operable to generate two signals430a,430bin one or more of the following combinations:

The two signals430a,430bcan be selected in accordance with a multiplexer control signal436a.

The two signals430a,430bare coupled to a phase difference module432operable to identify a phase difference between the two signals430a,430band operable to generate a phase difference signal432a. Circuits described in figures below describe arrangements that can be used as the phase difference module432.

A position decoder module434can be coupled to the phase difference signal432aand can generate a position signal434aindicative of a position (e.g., a rotation angle) of the target object404a,404b. To this end, in some embodiments, the position decoder module434can be a non-volatile memory device that can act as a decoder between the phase difference signal432aand the position signal434a.

An element selection circuit436can be coupled to an element selection signal438from outside of the magnetic field sensor400and can be operable to generate the multiplexer control signal436ato control which ones of the above-listed signals are used.

An output format module420can be coupled to one or more of the position signal434a, the speed signal412a, or the direction signal418a. The output format module420can be operable to generate a formatted output signal420aindicative of one or more of a position, a speed, or a direction of movement of the portions404a,404bof the target object.

The formatted output signal420acan be in any one of a variety of formats, including, but not limited to, SPI (serial peripheral interface), PWM (pulse width modulation), I2C, and SENT (Single Edge Nibble Transmission).

In some embodiments, position information carried by the formatted signal420ais present only during a time period proximate to a power up of the magnetic field sensor. In other embodiments, position information carried by the formatted signal420ais present only during a time period proximate to first movement of the portions404a,404bof the target object after they have stopped. Thereafter, the formatted signal can be indicative of only one or more of the speed or the direction of movement of the portions404a,404bof the target object.

Operation of the magnetic field sensor is described in figures below. However, let it suffice here to say that a phase difference between the above-listed two signals430a,430bis indicative of an absolute rotation angle of the target object404a,404b.

In some embodiments, some of the elements of the magnetic field sensor400can be omitted. For example, in some embodiments, there is no selection of the two signals430a,430b, and instead, the two signal430a,430bare predetermined and hard wired, in which case, the 4:2 multiplexer430, the element selection circuit436, and circuits that generate unused ones of the signals A, B, C, D, A′, B′, C′, D′ can be omitted.

In some embodiments, the AGC/AOA circuits410,424,446,454can be omitted and similar functions can instead be embedded within other modules, for example, within the phase difference module432.

In some embodiments, the first one or more magnetic field sensing elements406a,406b,406ccan consist of only two magnetic field sensing elements406a,406band the second one or more magnetic field sensing elements440a,440b,440ccan consist of only two magnetic field sensing elements440a,440b. In some embodiments, the first one or more magnetic field sensing elements406a,406b,406ccan consist of only one magnetic field sensing element406aand the second one or more magnetic field sensing elements440a,440b,440ccan consist of only one magnetic field sensing element440a.

Referring now toFIG. 5, an illustrative phase difference module500can be the same as or similar to the phase difference module432ofFIG. 4. It will be understood that a phase difference between two signals can be determined by a time difference between the two signals.

The phase difference module can be coupled to the two signals430a,430bofFIG. 4, which can be any of the two signals listed above.

If the signals A, B, C, D are used, then the phase difference module500can be coupled to the signals A or B and the signals C or D ofFIG. 4.

A threshold generator504can identify a threshold associated with the signal A or B and can generate a threshold signal504a. A threshold generator512can identify a threshold associated with the signal C or D and can generate a threshold signal512a. In some embodiments, the threshold generators504,512are operable to identify single thresholds, for example, at eighty, seventy, sixty, or fifty percent of as peak-to-peak range of respective input signals A, B, C, or D.

A comparator502can be coupled to the signal A or B and the threshold signal504aand can generate a two-state comparison signal502a. A comparator510can be coupled to the signal C or D and the threshold signal512aand can generate a two-state comparison signal510a.

A start/stop counter506can be coupled to the comparison signal502aat a start input node and can be coupled to receive the comparison signal510aat a stop input node, both nodes responsive to predetermined direction of state transitions. The start/stop counter506can generate a count signal506areceived at latches508operable to temporarily store the count signal506ato generate a latched count signal508a.

An oscillator514can generate a clock signal514areceived at a clock input node of the start/stop counter506.

A time delay circuit516can be coupled to the comparison signal510aand can generate a time delayed signal coupled to a reset input node of the start/stop counter506to reset the start/stop counter506shortly after the start/stop counter506is stopped by the comparison signal510a.

The latches508acan be latched upon a state of the comparison signal510abeing received at a latch input node of the latches508a.

Count values from the latches508are indicative of a phase between the two signals A or B and C or D, in arbitrary units.

In an alternative embodiment, the signals A or B and C or D are not received by the phase difference module500. In these embodiments, the signals A′ or B′ and C′ or D′ ofFIG. 4are received by the phase difference module500. The signals A′, B′, C′, and D′ are already two-state signals. The signal A′ or B′ can be received at the start node of the start/stop counter506instead of the comparison signal502a. The signal C′ or D′ can be received at the stop node of the start/stop counter506instead of the comparison signal502a.

The phase difference module500determines a phase difference between two signals by measuring a time difference between the two signals. Essentially, the phase difference module500can identify time differences between points on the signals302,304ofFIG. 3where they cross the threshold value306. Embodiments described in conjunction withFIGS. 6 and 7use other circuits to determine a phase difference between two signals.

Referring now toFIG. 6, another illustrative phase difference module600can be the same as or similar to the phase difference module432ofFIG. 4. The phase difference module600can include a correlation module602coupled to the signals A or B and the signals C or D ofFIG. 4. Correlation is a technique that can identify a phase difference between two signals. Thus, the correlation module602can generate a phase signal602a.

Referring now toFIG. 7, another illustrative phase difference module700can be the same as or similar to the phase difference module432ofFIG. 4. The phase difference module700can include a phase locked loop (PLL) module702coupled to the signals A or B and the signals C or D ofFIG. 4. A phase locked loop can identify a phase difference between two signals. Thus, the correlation module702can generate a phase signal702a.

Referring now toFIG. 8, in which like elements ofFIG. 4are shown having like reference designations, a magnetic field sensor800can be disposed proximate to the first and second portions404a,404bof the target object. The magnetic field sensor800is a reduced version of the magnetic field sensor400ofFIG. 4, and operates in substantially the same way.

A magnetic field sensing element804can be operable to generate a magnetic field signal804acoupled to an amplifier806. The amplifier806can be operable to generate an amplified signal806a.

An AGC/AOA module808can be coupled to the amplified signal806aand can generate a controlled signal808a, also indicated with a designation A.

A threshold generator812can be coupled to the controlled signal808aand can generate a threshold signal812a.

The controlled signal808aand the threshold signal812acan be coupled to input nodes of comparator810to generate a comparison signal810a, also indicated with a designation A′. In some embodiments, the comparison signal810ais a two state signal with high states and low states. The comparison signal810acan also be referred to as a speed signal for which a rate of transitions is indicative of a speed of rotation of the first and second portions404a,404bof the target object.

A magnetic field sensing element816can be operable to generate a magnetic field signal816acoupled to an amplifier818. The amplifier818can be operable to generate an amplified signal818a.

An AGC/AOA module820can be coupled to the amplified signal8018aand can generate a controlled signal820a, also indicated with a designation C

A threshold generator824can be coupled to the controlled signal820aa and can generate a threshold signal812a.

The controlled signal820aand the threshold signal824acan be coupled to input nodes of comparator822to generate a comparison signal822a, also indicated with a designation C′. In some embodiments, the comparison signal822ais a two state signal with high states and low states.

A phase difference module828can be coupled to the signals A and C or A′ and C′. The phase difference module can be the same as or similar to the phase difference module432ofFIG. 4. Because the signals A or C and A′ or C′ can be statically coupled to the phase difference module828, the phase difference module need not be preceded by the multiplexer430ofFIG. 4. However, in other embodiments, a multiplexer can be added to selected between the signals A or A′ and C or C′.

The phase difference module can be operable to generate a phase signal432aindicative of a phase difference between the signals A or A′ and C or C′.

A position decoder module830can be coupled to the phase signal828aa and can decode the phase signal828ato produce position signal830asimilar to the position signal432aofFIG. 4.

Referring now toFIG. 9, in which like elements ofFIG. 4are shown having like reference designations, magnetic field sensor900can employ other techniques to generate the speed and direction signals ofFIG. 4. The magnetic field sensor900can have a position detection module that can be similar to the position detection module ofFIG. 4, and that can generate a position signal930asimilar to the positions signal434aofFIG. 4indicative of a position (e.g., angle) of the portions404a,404bof the target object. It should be understood that, from the position signal930a, both speed of movement and direction of the movement of the portions404a,404bof the target object can be calculated. To this end, some of the circuits ofFIG. 4can be omitted as shown inFIG. 9.

A speed detection module934can be coupled to the position signal930aand can generate a speed signal934aindicative of a speed or rate of movement of the portions4040a,404bof the target object.

A direction detection module932can be coupled to the position signal930aand can generate a direction signal932aindicative of a direction of the movement of the portions4040a,404bof the target object.

An element selection module936and multiplexer control signal936acan be similar to the element selection module436and multiplexer control signal436aofFIG. 4.

An output format module920and formatted signal920acan be the same as or similar to the output format module and formatted signal420aofFIG. 4.

Referring now toFIG. 10, a magnetic field sensor1000can be illustrative of a mechanical arrangement of any of the magnetic field sensors of figures above.

The magnetic field sensor1000can include a first semiconductor substrate1002upon which can be disposed the first one or more magnetic field sensing elements406a,406b,406cofFIG. 4of804ofFIG. 8. The magnetic field sensor1000can also include a second semiconductor substrate1004upon which can be disposed the second one or more magnetic field sensing elements440a,440b,440cofFIG. 4 or 816ofFIG. 8. With the two substrates, the groups of magnetic field sensing elements can be more widely separated than would otherwise be possible if all of the magnetic field sensing elements were disposed on a single semiconductor substrate.

In some embodiments, other elements of the magnetic field sensor400ofFIG. 4 or 800ofFIG. 8can be disbursed among the first and second semiconductor substrates. However, in another embodiment, some of the other elements can be disposed upon an optional third semiconductor substrate1006.

The semiconductor substrates1002,1004,1006can be coupled to a base substrate1008, which can be comprised of a semiconductor or insulator (e.g., ceramic) material. The coupling to the base substrate can be made by solder balls, e.g.,1010, or the like. Interconnecting traces upon the base substrate1008can make interconnections between the semiconductor substrates1002,1004,1006.

The base substrate1008can be coupled to a base plate1012aof a lead frame1012with couplings, e.g.,1014, to make connection to leads, e.g.,1012b, of the lead frame1012. In some embodiments, the leads, e.g.,1012b, can be formed into a surface mount configuration.

In back biased arrangements used to sense a movement of a ferromagnetic target object, a permanent magnet1016can be disposed proximate to the substrates1002,1004,1006. In other embodiments used to sense a ring magnet, the permanent magnet1016can be omitted.

A solid molded enclosure1018can surround parts of the magnetic field sensor1000as shown.

In some alternate embodiments, the magnetic field sensors described above are disposed entirely upon one substrate.

Referring now toFIG. 11, a graph1100has a horizontal axis with a scale in units of rotation speed of the portions404a,404bof the target object ofFIG. 4in unit of revolutions per minute. The graph1100has a vertical axis with a scale in units of time shift per period in units of seconds. The time shift is essentially the shift identified inFIG. 3, where the shift changes with each cycle of the signals302,304.

A line1102is indicative of one of the portions, e.g.,404aofFIG. 4, of the target object having twenty teeth and the other portion having twenty-one teeth. A line1104is indicative of one of the portions, e.g.,404aofFIG. 4, of the target object having one hundred teeth and the other portion having one hundred one teeth. Other lines on the graph1100are at intervals of twenty teeth.

From the graph1100it can be seen that the shift per period is less for higher rotation speeds. Also, the shift per period is less for target objects with greater numbers of teeth (or poles). For embodiments using the time shift fromFIG. 3to determine absolute angle, a time resolution of the magnetic field sensor can limit the maximum allowable rotation speed at which absolute angles can be reliably determined. The graph1100serves to predict the maximum allowable rotation speed for a number of target combinations. For example, from the graph1100, for a magnetic field sensor that can resolve time shifts greater than or equal to one hundred microseconds, assuming a pair of targets with twenty and twenty one features (line1102), the maximum target speed would be approximately two thousand revolutions per minute.

Referring now toFIG. 12, a graph1200has a horizontal axis with a scale in units of absolute angle of the target object106ofFIG. 1, having two target object portions, in units of degrees, and a vertical axis with a scale in units of differential magnetic field in normalized arbitrary units related to that which would be experienced by two magnetic field sensing elements taken differentially. In some embodiments, the differential field can be identified by a difference of signals from the magnetic field sensing elements S1, S2, S3ofFIG. 2, e.g., S1-S2, which is like signal1202, and a difference of signals from the magnetic field sensing elements S4, S5, S6ofFIG. 2, e.g., S4-S5, which is like the signal1204.

The graph1200shows first and second signals1202,1204that are similar to the signals302,304ofFIG. 3. The absolute angle of the horizontal axis is similar to the time on the horizontal axis ofFIG. 3. Here, unlikeFIG. 3, the signals1202,1204are not compared to a threshold (e.g.,306ofFIG. 3), but instead, proximate (in time) crossings (e.g.,1206,1208, respectively) of the first and second signals1202,1204are identified.

Like the time shifts shown onFIG. 3, which change depending upon rotation angle of the target object, here, it should be apparent that vertical locations of the crossings (e.g.,1206,1208) change with rotation angle of the target object. In order to uniquely identify all absolute angles of the target, the magnetic field sensor can distinguish between crossings at which the slope of signal1204is positive and crossings at which the slope of signal1204is negative at the time of each crossing. Magnetic field sensors described below in conjunction withFIGS. 14 and 21use this behavior. Magnetic field sensors described herein can use one, the other, or both the crossings at the positive slope of the signals1204and crossings at the negative slope of the signal1204.

Referring now toFIG. 13, a graph1300has the same axes as those of the graph1200ofFIG. 12. Here, however, the horizontal axis has a wider angle scale. Points1302are indicative of signal crossings for which the slope of signal1204is positive, while points1304are indicative of signal crossings for which the slope of signal1204is negative. These points are like those ofFIG. 12, but are visible throughout a range of angular rotations of the target object106ofFIGS. 1 and 2. It should be apparent that some embodiments can use either the crossings1302at the positive slope of the signal1204or crossings1304at the negative slope of the signal1204. Either can uniquely identify the absolute angle.

Other embodiments can use a difference between proximate crossings, e.g. points1206,1208ofFIG. 12, in order to determine the absolute position of the target. In this case, it is both the difference between proximate crossings and the sign of the difference that are indicative of the angle of rotation. It should be apparent that these embodiments can use both the crossings at the positive slope of the signal1204and crossings at the negative slope of the signal1204.

Referring now toFIG. 14, in which like elements ofFIG. 4have like reference designations, the position detection mode428ofFIG. 4is replaced by a position detection module1402that makes use of the signal crossing difference ofFIGS. 12 and 13.

The position detection module can include a 4:2 multiplexer1404similar to the 4:2 multiplexer430ofFIG. 4. However, only the signal A or B and C or D are received by and used by the 4:2 multiplexer1404.

The 4:2 multiplexer1404can select and generate two signals (see, e.g., signal1202,1204ofFIG. 12) from the group of two signals:

The selection is determined in accordance with a multiplexer control signal436a.

The selected two signals can be coupled to a crossing detection module1406operable to detect some of or all of the crossings of the two signals received by the crossing detection module. An illustrative crossing detection module is described below in conjunction with FIG.15. The crossing detection module1406can be operable to generate a crossing signal1406aindicative of the detected crossings of the two signals.

Optionally, (shown as phantom lines) an amplitude difference module1408can identify a difference of amplitudes between proximate crossings of the crossing signal1406a. The amplitude difference module1408can generate a difference signal1408aindicative of the difference of amplitudes, which, as identified in conjunction withFIGS. 12 and 13, is indicative of an angle of rotation of the first and second portions404a,404bof the target object.

A position decoder module1210can be coupled to the crossing signal1406a(or optionally, to the difference signal1408a) and can be operable to generate a position signal1410aindicative of a position (e.g., angular position) of the target object.

Output format module420can generate a formatted signal that can be the same as or similar to the formatted signal420aofFIG. 4.

Referring now toFIG. 15, an illustrative crossing detection module1500can include a comparator1502to generate a crossing signal1502aindicative of crossings of the signals A or B and C or D. The crossing signal1502acan be the same as or similar to the crossing signal1406aofFIG. 14.

Referring now toFIGS. 16 and 17, graphs1600and1700each include a horizontal axis with a scale in units of rotation angle of the portions404a,404bof the target object ofFIG. 14in degrees and each include a vertical axis with a scale in units of normalized differential magnetic field at which crossing points of two signals occur (e.g., points1304inFIG. 13). Points1602are indicative of only one set of crossings of the signals1202and1204ofFIG. 12, e.g., crossings1304ofFIG. 13. The other set of crossings, e.g.,1302ofFIG. 13is omitted for clarity.

In some embodiments, a first signal is generated by a difference of signals from the magnetic field sensing elements S1, S2, S3ofFIG. 2, e.g., S1-S2, which is like signal1202, and a second signal crossing the first signal is generated by a difference of signals from the magnetic field sensing elements S4, S5, S6ofFIG. 2, e.g., S4-S5.

A plurality of curves1602on the graph1600is indicative of a back-biased arrangement for sensing rotation of a ferromagnetic gear having teeth with ninety degree corners, for different air gaps between the magnetic field sensor1400ofFIG. 14and the target object, the air gaps spanning between 0.5 mm and 3.0 mm in increments of 0.5 mm. The data inFIG. 16were simulated assuming a pair of targets with sixty and sixty-one teeth.

Similarly, a plurality of curves1702on the graph1700is indicative of a non back-biased arrangement for sensing rotation of a ring or circular magnet having north and south poles around a circumference of the ring or circular magnet, for different air gaps between the magnetic field sensor1400ofFIG. 14and the target object, the air gaps spanning between 0.5 mm and 3.0 mm in increments of 0.5 mm. The data inFIG. 16were simulated assuming a pair of ring-magnet targets with sixty and sixty-one pole pairs.

An illustrative installed unit-to-unit tolerance for the air gap is about +/−0.5 mm.

For both of the graphs1600,1700it should be apparent that the variation of crossing points with rotation angle may not be straight line linear and may change depending upon air gap. Circuits and techniques described below in conjunction withFIGS. 19, 20, and 21can mitigate this variation.

Referring now toFIG. 18, a graph1800has a horizontal axis with a scale in units of rotation angle in degrees of the portions404a,404bof the target object described above in conjunction withFIG. 14. The graph1800also has a vertical axis with a scale in units of crossing point change per tooth-valley period for one set of crossings, e.g., crossings1304ofFIG. 13. Points1802are indicative of rates of change of the one set of crossings of the two signals1202,1204ofFIG. 12, e.g., crossings1304ofFIG. 13.

Referring briefly toFIG. 13, for two target object portions, e.g.,404a,404bofFIG. 14, that differ by one tooth or one pole pair, a crossing point change per period of curve1304is highest near one hundred eighty degrees of rotation of the target object and lowest for rotation angles near zero and three hundred sixty degrees of rotation.

A limiting factor for accurate determination of the absolute angle in this embodiment is the capability of the magnetic field sensor to resolve the differential field at which each crossing point occurs. This is the most difficult for rotation angles near zero and three hundred sixty degrees of rotation, where the crossing point change per period is small, as shown inFIG. 18.

Referring now toFIG. 19, a graph1900, which is like the graph1600ofFIG. 16, includes a horizontal axis with a scale in units of rotation angle of the portions404a,404bof the target object ofFIG. 14in degrees, and a vertical axis with a scale in units of differential magnetic field crossing points (seeFIG. 16for an explanation of the vertical axis).

With regard to accuracy deficiencies at some rotation angles described above in conjunction withFIG. 18, relatively high sensitivity can be maintained at all rotation angles if a strategy is adopted using different pairs of sensing elements inFIG. 2at different rotation angles of the target object, e.g. S3-S2crossing S5-S4(1902aand1902b) at some rotation angles, and, S2-S1crossing S6-S5(1904aand1904b) at other rotation angles.

This strategy of using offset pairs of sensing elements shifts the absolute angle at which the maximum slope of the simulated data inFIG. 19occurs away from one hundred eighty degrees when compared to the simulations inFIGS. 16-17.

FIG. 20is similar toFIG. 18. A set of crossing point changes per tooth-valley period2002shows slopes of the set of points1902a,1902bofFIG. 19. A set of crossing point changes per second2004shows slopes of the set of points1904a,1904bofFIG. 19.

It is desirable to maintain a high rate of change of the crossings of the two signals to maximize angle sensitivity. Thus, for example, for rotation angles of the target object between about zero and one hundred eighty degrees, the set of points2002can be used according to crossings generated by S3-S2crossing S5-S4(seeFIGS. 1 and 2), and for angles of the target object between about one hundred eighty degrees and three hundred sixty degrees, the set of points2004can be used according to crossings generated by S2-S1crossing S6-S5.

Referring now toFIG. 21, in which like elements ofFIGS. 4 and 14are shown having like reference designations, a magnetic field sensor2100is like the magnetic field sensor1400ofFIG. 14, except that the element selection circuit436ofFIG. 14is replaced by a position range detection circuit2102that can generate a multiplexer control signal2102athat can change connections of the 4:2 multiplexer1404during a rotation of the portions404a,404bof the target object. In some embodiments, the magnetic field sensor2100can control the 4:2 multiplexer1404to use signals A and C during a first selected one hundred eighty degrees of rotation of the target object and to use signals B and D during a second selected one hundred eighty degrees of rotation of the target object. Other signal combinations are also possible.

The position decoder module1410ofFIG. 14can also be replaced by a position decoder module2101that can account for the phase shift of the crossing signals depicted inFIGS. 19 and 20in accordance with different signals selected by the 4:2 multiplexer1404.

Referring now toFIG. 22, a magnetic field sensor2204can sense an absolute position of a target object2202. The target object2202has a first portion2202ahaving a first quantity of target features and a second portion2202bhaving a second quantity of target features different than the first quantity. The first and second portions2202a,2202bare proximate and mechanically fixed together. The target object2202, including the first and second portions2202a,2202b, is capable of a movement (e.g., a rotation). The magnetic field sensor2204can include one or more magnetic field sensing elements disposed proximate to a mechanical intersection2202cto sense both the first and second portions2202a,2202bof the target object2202with the same one or more magnetic field sensing elements. The one or more magnetic field sensing elements are operable to generate a first magnetic field signal responsive to the movement of both the first and second portions2202a,2202b. Described in conjunction withFIG. 25below, the magnetic field sensor2202can include a position detection module operable to use the first magnetic field signal to generate a position signal (i.e., values) indicative of the absolute position and an output format module coupled to receive the position value and to generate an output signal from the magnetic field sensor indicative of the absolute position.

The magnetic field sensor2204is disposed at a different position relative to a target object2202than that shown inFIGS. 1 and 2. However, the target object2202can be the same as or similar to the target object106ofFIGS. 1 and 2. Unlike the magnetic field sensor102ofFIGS. 1 and 2, the magnetic field sensor2204is disposed proximate to the junction2202cbetween first and second portions2202a,220bof the target object2202.

Referring now toFIG. 23, in which like elements ofFIG. 22are shown having like reference designations, the magnetic field sensor2204is disposed proximate to a junction2202cbetween first and second portions2202a,2200bof the target object2202. In this view, it can be seen that, at some rotations of the target object, valleys of the first portion2202aof the target object2202are proximate to valleys of the second portion2202b, and at other rotations of the target object, valleys of the first portion2202aare proximate to teeth of the second portion2202b.

The magnetic field sensor2204can experience influence from the first and second portions2202a,2202btogether at the same time.

While the target object2202is shown as a gear having teeth and valleys, in other embodiments, a ring or circular magnet can be used with alternating north and south poles around its circumference.

Referring now toFIG. 24, a graph2400has a horizontal axis with a scale in units of rotation angle of the target object2202ofFIGS. 22 and 23. The graph2400also has a vertical axis with a scale in units of differential magnetic field in Gauss experienced by the magnetic field sensor2204ofFIGS. 1 and 2.

The graph2400has two signals2402,2404. The two signals are signals generated within the magnetic field sensor2204as the target object rotates. At some rotations of the target object the magnetic field sensor2204is proximate to like features of the two portions2202a,2202bof the target object2200, e.g., teeth to north poles. At other rotations, the magnetic field sensor is proximate to opposing features, e.g., a tooth and a valley or a north pole and south pole. An amplitude of one of or both of the signals2402,2404can be detected by a magnetic field sensor25described below.

Referring now toFIG. 25, in which like elements ofFIG. 4are shown having like reference designations, a magnetic field sensor2500can be disposed proximate to the target object2202ofFIGS. 22 and 23.

The magnetic field senor2500can generate the amplified signals408a,422aofFIG. 4, also identified as A″ and B″, similar to signals A and B ofFIG. 4. The signals A″ and B″ can be received by the speed/direction module414ofFIG. 4to generate the speed signal412aand the direction signal418aofFIG. 4.

A maximum peak-to-peak detection module2502can receive the amplified signal408aand can identify and generate a maximum peak-to-peak value2502aof the amplified signal408adetermined as the target object2200rotates.

A non-volatile memory2504, e.g., an EEPROM, can store the maximum peak-to-peak value2502a. The non-volatile memory2504is operable to provide a stored maximum peak-to-peak value2504a, also identified as a signal E.

A maximum peak-to-peak detection module2506can receive the amplified signal422aand can identify and generate a maximum peak-to-peak value2506aof the amplified signal422adetermined as the target object2200rotates.

A non-volatile memory2508, e.g., an EEPROM, can store the maximum peak-to-peak value2506a. The non-volatile memory2508is operable to provide a stored maximum peak-to-peak value2508a, also identified as a signal F.

A position detection module2510can include an amplitude detection module2512coupled to at least one of the signal A″ or the signal B″ and coupled to at least one of the stored maximum peak-to-peak values E or F. The amplitude detection module2512can be operable to identify a relative amplitude of at least one of the signal A″ or the signal B″ in view of at least one of the stored maximum peak-to-peak values E or F. The relative amplitude can be indicative of a rotation angle of the target object. See alsoFIG. 24. The amplitude detection module2512can be operable to generate an amplitude signal2512a(i.e., one or more amplitude values) indicative of the rotation angle.

A position decoder module2514can be coupled to the amplitude signal2512aand can be operable to generate a position signal2514a(i.e., position values) indicative of the rotation angle.

An output format module can be coupled to at least one of the position signal2514a, the speed signal412a, or the direction signal418aand can be operable to generate an output signal2516aindicative of at least one of the speed of rotation, the direction of rotation, and the absolute rotation angle of the target object.

Characteristics of the output signal2516acan be the same as or similar to characteristics of the output signal420aofFIG. 4described above.

In some embodiments, the nonvolatile memory2504can be coupled to a “set E” signal2518to set the maximum peak-to-peak value stored in the non-volatile memory2504to an initial value at start up. Similarly, in some embodiments, the nonvolatile memory2508can be coupled to a “set F” signal2520to set the maximum peak-to-peak value stored in the non-volatile memory2508to an initial value at start up. Values can be updated and stored in the nonvolatile memories2504,2508during run time of the magnetic field sensor2500.

In some embodiments, some of the electronic circuits of the magnetic field sensor2500can be omitted. For example, magnetic field sensing element406b, amplifier422, maximum peak-to-peak detection module2506, and nonvolatile memory2508can be omitted. In this case, some of the speed/direction module414can also be omitted.

It should be appreciated thatFIG. 26shows a flowchart corresponding to the below contemplated technique which would be implemented in a magnetic field sensor (e.g.,FIGS. 25 and 27). Rectangular elements (typified by element2602inFIG. 26), herein denoted “processing blocks,” represent computer software instructions or groups of instructions. Diamond shaped elements (typified by element2614inFIG. 26), herein denoted “decision blocks,” represent logic, or groups of logic, which affect the execution of processing blocks.

Referring now toFIG. 26, with reference toFIG. 25, a process2600can be used in the magnetic field sensor2500ofFIG. 25. At block2602, initial values can be loaded into the EEPROM2504an/or into the EEPROM2508via the signal2518and/or the signal2520. The initial values can be representative of a predetermined approximate maximum peak-to-peak value of the signals A and/or B.

At block2604, the stored maximum peak-to-peak values can be recalled from the EEPROM2504and/or the EEPROM2508and conveyed to the amplitude detection module2512.

At block2606, the amplitude detection module can measure values of amplitudes of the signals A″ and/or B″ as the target object2200rotates.

At block2608the amplitude detection module can compare the measured value(s) of the amplitude with the stored maximum peak-to-peak value(s) from the EEPROM2604and/or the EEPROM2508.

At block2618, if the measure amplitude(s) is/are not larger than the stored maximum peak-to-peak values(s) then at block2618, the measured amplitude(s) can be used according toFIG. 24to determine a rotation angle of the target object2200by determining how much smaller the measured amplitude value(s) is/are than the stored maximum peak-to-peak value(s).

At block2620, using the position decoder module2514, the calculated amplitude difference(s) can be converted into a position signal (i.e., position values)2514a. Then, the process2600can return to block2606.

On the other hand, if at block2610, the measured amplitude values(s) is/are greater than the stored maximum peak-to-peak value(s), then it is known that the stored maximum peak-to-peak value(s) is/are not correct. Thus, the process moves to block2612, where the maximum peak-to-peak value(s) is/are updated accordingly, but not yet sent to the EEPROM(S)2504and or2508for storage.

At block2614, predetermined conditions of the magnetic field sensor can be examined. For example, the updated maximum peak-to-peak values can be examined to determine if they are within a predetermined range of maximum peak-to-peak that is proper. An improper maximum peak-to-peak value may be indicative of for example, a malfunctioning magnetic field sensing element406a,406b,406c. An improper maximum peak-to-peak value may also be indicative of only a momentary electrical or magnetic noise spike in the signals408a,422a. For another example, in some embodiments, the magnetic field sensor can include a temperature sensor and, if the temperature is not within predetermined limits, updates to the stored maximum peak-to-peak value(s) may be stopped. For another example, in some embodiments, the magnetic field sensor can perform only one update to the stored maximum peak-to-peak value(s) per power cycle of the magnetic field sensor.

At block2614, if the predefined (i.e., predetermined) conditions are met, then the process proceeds to block2616, where maximum peak-to-peak value(s) stored in the EEPROMS(s)2504and/or2508is/are updated. The process returns to block2604.

On the other hand, if at block2614, the predefined conditions are not met, then the EEPROM(s)2504and/or2508are not updated and the process returns to block2606. The process can also generate a flag value to indicate that the predefined conditions were not met.

From language above should be apparent that only one of the signals A″, B″ and one of the signals E″, F″ is necessary. However, if they are all present, the magnetic field sensor2500can calculate two amplitude differences and two position signals (values) comparable to position signal2514a. In this case, the two position values can be combined, for example, averaged together, or they can be separately provided as part of the formatted output signal2516a.

Referring now toFIG. 27, in which like elements ofFIGS. 4 and 25are shown having like reference designations, a magnetic field sensor2700can generate and use only the signal A″ and the stored maximum peak-to-peak value E″. This arrangement should be apparent from the discussion above in conjunction withFIG. 26.

An output format module2712can be coupled to a speed signal2171agenerated by a speed module2717. This arrangement is similar to that described above in conjunction withFIG. 8.

Referring now toFIG. 28, a magnetic field sensor2800can be like the magnetic field sensor2500,2700. The magnetic field sensor2800can include a single semiconductor substrate2808coupled with solder balls2804or the like to a mounting plate2806aof a lead frame2806.

In back-biased arrangement in which the target object2200is a ferromagnetic object, e.g. a gear, the magnetic field sensor2800can include a permanent magnet2808. In other back-biased arrangements, the magnet2808can be external to the magnetic field sensor2800. For non back-biased arrangements in which the target object is a ring or circular magnet, the permanent magnet2808can be omitted.

A solid molded enclosure2810can surround parts of the magnetic field sensor2800as shown.

Referring now toFIG. 29, a flat target object2900can include first and second portions2900a,2900b, each having a different quantity of target features (e.g., teeth and valleys or magnetic poles).

A magnetic field sensor2902(here showing only a substrate) can be like the magnetic field sensor102ofFIGS. 1 and 2, wherein a first one or more magnetic field sensing elements is disposed proximate to the first portion2900aand a second one or more magnetic field sensing elements are disposed proximate to the second portion2900b.

Also shown, a different magnetic field sensor2904(here showing only a substrate) can be like the magnetic field sensor2204ofFIGS. 22 and 23, wherein one or more magnetic field sensing elements is disposed proximate to a boundary between the first and second portions2900a,2900b.

Movement of the target object2900can be parallel to a line2906.

For back-biased arrangements, the target features of the target object2900can be teeth and valley of a gear. For non back-biased arrangements, the target features of the target object2900can be north and south poles of a multi-pole magnet.

Circuits and techniques described in conjunction with figures above apply equally well to the flat target object2900as they do to the round target objects described above.