Patent Publication Number: US-11047928-B2

Title: Methods and apparatus for frequency effect compensation in magnetic field current sensors

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     FIELD 
     This disclosure relates generally to magnetic field current sensors, and, more particularly, to magnetic field current sensors having frequency effect compensation. 
     BACKGROUND 
     Some conventional current sensors are positioned near a current-carrying conductor to sense a magnetic field generated by the current through the conductor. The current sensor generates an output signal having a magnitude proportional to the magnetic field induced by the current through the conductor and thus, indicative of the current through the conductor. 
     The accuracy with which a magnetic field current sensor senses an intended current can be affected by the frequency of a varying current through the conductor. In particular, a varying current (even of fixed magnitude) generates a varying magnetic field and a varying magnetic field tends to generate eddy currents. Eddy currents can alter the current density distribution in the conductor, thereby modifying the magnetic field distribution as compared to the field distribution associated with a DC current, and also modifying the measured magnetic field and the accuracy of the current measurement. As a result, conventional magnetic field current sensors tend to have a specified current frequency range of operation. 
     SUMMARY 
     The present disclosure provides a current sensor operable to accurately sense current over a wide range of current frequencies. A coupling factor between the sensor and the conductor is characterized over the range of frequencies and is used to compensate for the effect of the current frequency. 
     In accordance with the disclosure, a current sensor having one or more magnetic field sensing elements configured to generate a magnetic field signal indicative of a magnitude of a sensed magnetic field, wherein the sensed magnetic field is related to a magnitude and frequency of a current through a conductor. A signal path is responsive to the magnetic field signal and includes a compensator configured to apply a compensation factor to the magnetic field signal to generate a sensor output signal indicative of the magnitude of the current and substantially independent of a frequency of the current. The sensed magnetic field is related to the magnitude of the current by a coupling factor and the signal path is responsive to a characterization of the coupling factor over a range of frequencies of the current in order to determine the compensation factor to be applied. 
     The magnetic field sensor may include one or more of the following features alone or in combination. The characterization of the coupling factor may be generated based on one or both of simulating operation of the current sensor or testing of the current sensor. In embodiments, the current sensor may include a frequency measurement circuit to measure the frequency of the current. A look-up table may be provided in which the characterization of the coupling factor is stored. The signal path may include a processor and the compensation factor may be determined by the processor using the look-up table in response to the measured frequency of the current. A memory may be configured to store an approximating function of the characterization of the coupling factor. The signal path may include a processor and the compensation factor may be determined by the processor computing the approximating function in response to the measured frequency. In embodiments, the signal path may include a filter having an inverse frequency response with respect to a transfer function of the coupling factor. 
     The magnetic field sensing elements and the signal path may be integrated into a package and the conductor may be integrated into the same package. The magnetic field sensing elements and the signal path may be integrated into a package and the conductor may be external to the package. The magnetic field sensing elements may include one or more of magnetoresistance elements, Hall effect elements, or fluxgate element. The magnetoresistance elements may include at least one of Indium Antimonide (InSb), a giant magnetoresistance (GMR) element, an anisotropic magnetoresistance (AMR) element, a tunneling magnetoresistance (TMR) element or a magnetic tunnel junction (MTJ) element. In embodiments, at least one first magnetic field sensing element is spaced from at least one second magnetic field sensing element, the at least one first magnetic field sensing element is configured to generate at least one first magnetic field signal indicative of a distance between the at least one first magnetic field sensing element and the conductor and at least one second magnetic field sensing element is configured to generate at least one second magnetic field signal indicative of a distance between the at least one second magnetic field sensing element and the conductor and the signal path includes a circuit responsive to the at least one first magnetic field signal and to the at least one second magnetic field signal and configured to generate a difference signal indicative of a difference between the at least one first magnetic field signal and the at least one second magnetic field signal, wherein the difference is indicative of the magnitude of the current and substantially independent of the frequency of the current. 
     In another aspect, a method for sensing a current through a conductor includes generating a magnetic field signal in response to a magnetic field associated with the current and applying a compensation factor to the magnetic field signal to generate a sensor output signal indicative of the magnitude of the current and substantially independent of a frequency of the current. The sensed magnetic field is related to the magnitude of the current by a coupling factor and the method may further include characterizing the coupling factor over a range of frequencies of the current and determining the compensation factor based on the characterization of the coupling factor. 
     Features of the method may include one or more of the following alone or in combination. In embodiments, the method may further include measuring a frequency of the current and using the measured frequency to determine the compensation factor to be applied to the magnetic field signal. In embodiments, applying the compensation factor to the magnetic field signal may include filtering the magnetic field signal with a filter having an inverse transfer function with respect to a transfer function of the coupling factor. 
     According to a further aspect, a current sensor includes means for sensing a magnetic field generated by a current through a conductor and generating a magnetic field signal related to a magnitude and frequency of the current and means for applying a compensation factor to the magnetic field signal to generate a sensor output signal indicative of the magnitude of the current and substantially independent of a frequency of the current. The sensed magnetic field is related to the magnitude of the current by a coupling factor and the current sensor may further include means for characterizing the coupling factor over a range of frequencies of the current in order to determine the compensation factor. In embodiments, the current sensor may further include means for measuring the frequency of the current and using the measured frequency to determine the compensation factor. In embodiments, the compensation factor applying means may include a filter having a transfer function inversely related to a transfer function of the coupling factor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. 
         FIG. 1  is a simplified block diagram of an example magnetic field current sensor according to the disclosure; 
         FIG. 1A  is a simplified block diagram of an embodiment of the current sensor of  FIG. 1 ; 
         FIG. 1B  is a simplified block diagram of another embodiment of the current sensor of  FIG. 1 ; 
         FIG. 2  is a graph illustrating a coupling factor variation between current and magnetic field over frequency for an example current sensor with the variation in the coupling factor shown in percentage; 
         FIG. 2A  is a graph illustrating a compensation factor for the example current sensor characterized by  FIG. 2 ; 
         FIG. 3  is a graph illustrating a coupling factor between current and magnetic field over frequency for an example current sensor with the coupling factor shown in magnitude; 
         FIG. 3A  is a graph illustrating a compensation factor for the example current sensor characterized by  FIG. 3 ; 
         FIG. 3B  is a graph illustrating a response to application of the compensation factor of  FIG. 3A  to the current sensor characterized by  FIG. 3 ; 
         FIG. 4  is a block diagram of an example current sensor; and 
         FIG. 5  is a block diagram of another example current sensor. 
     
    
    
     DETAILED DESCRIPTION 
     The features and other details of the disclosure will now be more particularly described. It will be understood that any specific embodiments described herein are shown by way of illustration and not as limitations of the concepts, systems and techniques described herein. The principal features of this disclosure can be employed in various embodiments without departing from the scope of the concepts sought to be protected. 
     Referring to  FIG. 1 , a magnetic field current sensor system  10  includes a current sensor  12  and a conductor  20  configured to carry a current for sensing by the current sensor. The current through the conductor  20  generates a magnetic field sensed by the current sensor  12 . The current sensor  12  includes one or more magnetic field sensing elements  16  configured to generate a magnetic field signal  18  indicative of a magnitude of a sensed magnetic field. A signal path  30  is responsive to the magnetic field signal  18  and includes a compensator  34  configured to apply a compensation factor to the magnetic field signal to generate a sensor output signal  40  indicative of the magnitude of the current and substantially independent of a frequency of the current. 
     As used herein, the term “magnetic field sensing element” (e.g., the one or more magnetic field sensing elements  16 ) 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, a magnetotransistor, or a fluxgate element. 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. As is also known, 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). 
     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. 
     Various configurations and features of the current sensor  12  are shown and described below in connection with  FIGS. 4 and 5 . Suffice it to say here that the current sensor  12  can be a linear or differential sensor. 
     Conductor  20  can be an integral conductor (e.g., integrated into a common package, such as an integrated circuit package, with the current sensor  12 ). Alternatively, the conductor can be an external conductor (e.g., positioned external to the current sensor package but proximal to the package). Example external conductors can take various forms, such as a printed circuit board conductor or a busbar, as examples. 
     The magnetic field sensed by the sensing element(s)  16  is related to the magnitude of the current I through the conductor by a coupling factor CF (shown pictorially by an arrow labeled  14 ). The coupling factor  14  refers to the relationship between the magnitude of the current I and the resulting magnetic field H around the conductor and can be expressed by α in the following equation (1):
 
 H (ƒ,  I )=α(ƒ)× I   (1)
 
where I is the current through the conductor  20  and ƒ is the frequency of the current I. At DC, α is constant over current magnitude. However, the coupling factor a varies with frequency of the current. Hence, knowing the DC coupling factor (i.e, α(0)) and measuring the field H is not enough to accurately measure the current over frequency.
 
     According to the disclosure, the coupling factor α  14  is characterized over a range of frequencies of the current I through the conductor  20  in order to thereby generate information about the frequency effects on current measurement. This characterization is used to determine a compensation factor to be applied by the compensator  34 . 
     Referring also to  FIG. 2 , a characterization of the coupling factor α  14  for an example rectangular bus bar conductor is shown in a plot  200  having a horizontal axis representing the frequency of the current I with a scale in units of Hertz and a vertical axis representing the variation of the coupling factor α  14  with a scale in units of percentage variation. Also shown in  FIG. 2 , is a coupling factor characterization  208  that can be determined by an approximating function. 
     The coupling factor α  14  can be affected by various factors including, but not limited to placement of the sensing elements  16  relative to the conductor  20 , the conductor shape, material and dimensions. Therefore, busbar and sensor placement can be optimized to obtain different frequency response. 
     Various techniques are possible to generate the coupling factor characterization. For example, the coupling factor α  14  can be characterized by simulating operation of the current sensor  12  and/or by testing the current sensor operation, for example in a manufacturing setting. 
     In embodiments, the coupling factor characterization can be stored, for example in a memory (e.g., EEPROM)  24  internal or external to the current sensor  12 . In some embodiments, the characterization is stored in memory in the form of a look-up table containing a plurality of coupling factor values, each associated with a corresponding current frequency. Alternatively, in some embodiments, the characterization is stored in the form of an approximating function that is used to compute the coupling factor based a mathematical function that characterizes a relationship between the current frequency and the generated field. 
     Referring also to  FIG. 1A , a current sensor system  50  includes a current sensor  52  and conductor  20  configured to carry a current for sensing by the current sensor. Current sensor  52  represents an embodiment of the current sensor  12  of  FIG. 1  and includes one or more magnetic field sensing elements  16  configured to generate a magnetic field signal  18  indicative of a magnitude of a sensed magnetic field. 
     The signal path of current sensor  52  includes a compensator in the form of a gain element  60  by which the compensation factor can be applied to the magnetic field signal  18  to generate a sensor output signal  66  indicative of the magnitude of the current and substantially independent of a frequency of the current. The gain element  60  can be implemented in the analog and/or digital domain. In some embodiments, the gain element  60  can be an amplifier circuit. In some embodiments, the gain element  60  can be implemented with a processor. 
     As used herein, the term “processor” (e.g., a processor implementation of gain element  60 ) 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, for example, in a specially programmed microprocessor, a digital signal processor (DSP), or an application specific integrated circuit (ASIC), which can be an analog ASIC or a digital ASIC. Additionally, in some embodiments the “processor” can be embodied in configurable hardware such as field programmable gate arrays (FPGAs) or programmable logic arrays (PLAs). In some embodiments, the “processor” can also be embodied in a microprocessor with associated program memory. Furthermore, in some embodiments the “processor” can be embodied in a discrete electronic circuit, which can be an analog circuit, a digital circuit or a combination of an analog circuit and a digital circuit. The “controller” described herein may be provided as a “processor.” 
     Current sensor  52  includes a frequency detector  64  coupled to receive the magnetic field signal  18  and configured to measure the frequency of the current through the conductor  20 . The measured frequency (represented by reference character  62 ) can be used along with the coupling factor characterization (as may be stored in memory) by the element  60  (as may be a processor) to determine the compensation factor to be applied to the magnetic field signal  18  in order to thereby generate the sensor output signal  66  by cancelling the effect of the current frequency so that the output signal  66  is indicative of the current magnitude and independent of the current frequency. 
     Various circuitry and techniques are suitable for measuring the current frequency. By way of non-limiting examples, the frequency detector  64  can be provided as a circuit configured to measure the time between two consecutive like peaks of the magnetic field signal  18  (e.g., to measure a time between consecutive positive peaks of the magnetic field signal or to measure a time between consecutive negative peaks of the magnetic field signal) or to measure the time between two consecutive like crossings of a predetermined threshold level (e.g., to measure a time between the consecutive positive going, or rising signal crossings of a threshold at a percentage of the peak-to-peak magnetic field signal). Another example frequency detector  64  can utilize a frequency-to-voltage (F/V) converter circuit to provide voltage input proportional to signal frequency within the device. 
     It will be appreciated that the sensor output signal  66  is related to the measured magnetic field H by constant k and further, that when the current to be measured is a varying current, the output signal  66  can be represented as follows:
 
 V   OUT (ƒ, I )= k (ƒ)· H (ƒ,  I )  (2)
 
where the output signal V OUT    66  and the magnetic field H are both functions of the frequency ƒ of the current and the magnitude of the current I and the constant k is likewise a function of the current frequency. The compensation factor to be applied to the magnetic field signal  18  in order to generate a sensor output signal that is indicative of the current magnitude and independent of the current frequency is given by the term k(f) in equation (2).
 
     The variation of the coupling factor a over frequency (as shown for example in  FIG. 2 ) can be expressed as Δα(f) according to the following equation (3): 
     
       
         
           
             
               
                 
                   
                     Δα 
                     ⁡ 
                     
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                       f 
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     In order to compensate for the effect of frequency of the current, the compensation factor to be applied, k(f) should have an inverse relationship with respect to the coupling factor so as to linearize the native coupling factor frequency response. For example, in order to compensate for the example coupling factor variation shown in  FIG. 2 , a compensation factor k(f) having an inverse characteristic with respect to  FIG. 2  should be applied. Such a compensation factor k(f) is illustrated by the plot  250  shown in  FIG. 2A  having a horizontal axis representing the frequency of the current I with a scale in units of Hertz and a vertical axis representing the compensation factor with a scale in arbitrary units. 
     The compensation factor k(f) can be determined according to equation (4): 
                     k   ⁡     (   f   )       =     G     1   +       Δ   ⁢     α   ⁡     (   f   )           1   ⁢   0   ⁢   0                   (   4   )               
where ƒ is the frequency of the current, G represents the gain of the sensor signal path, and Δα is the variation of the coupling factor a over frequency in percent.
 
     By applying the compensation factor k(f) to the magnetic field signal  18 , the sensor output signal  66  can be expressed as follows:
 
 V   OUT ( I )= G ·α(0)· I   (5)
 
     As will be appreciated from consideration of equation (5), the resulting sensor output signal  66  is independent of the current frequency, as is desired. Thus, by determining and applying the compensation factor k(f), dependence of the sensor output signal  66  on the frequency of the current can be eliminated. 
     Referring also to  FIG. 1B , another current sensor system  100  includes a current sensor  80  and conductor  20  configured to carry a current for sensing by the current sensor. Current sensor  80  represents another embodiment of the current sensor  12  of  FIG. 1  and includes one or more magnetic field sensing elements  16  configured to generate a magnetic field signal  18  indicative of a magnitude of a sensed magnetic field. 
     The signal path of current sensor  80  includes a compensator in the form of a filter  84  by which the compensation factor can be applied to the magnetic field signal  18  to generate a sensor output signal  90  indicative of the magnitude of the current and substantially independent of a frequency of the current. The current sensor  80  does not require detection of the current frequency. As will be explained, filter  84  can be designed to have an opposite, or inverse transfer function with respect to the coupling factor so as to “cancel” the effects of the coupling factor transfer function. 
     Although shown as a single filter  84 , it will be appreciated that more than one filter can be used to apply the compensation factor. It will also be appreciated that the filter  84  can be an analog or digital filter, FIR or IIR, depending on application requirements. 
     Referring also to  FIG. 3 , a characterization of the coupling factor α  14  for an example rectangular bus bar conductor is shown in a plot  300  having a horizontal axis representing the frequency of the current I with a scale in units of Hertz and a vertical axis representing the coupling factor magnitude in decibels. With knowledge of the coupling factor characterization  300 , filter  84  can be designed to have an opposite, or inverse transfer function so as to “cancel” the effects of the coupling factor transfer function. More particularly, the transfer function of the characterized coupling factor as shown in  FIG. 3  can be used to determine an optimized filter type, order and coefficients to provide an inverse transfer function. 
     From the coupling factor variation over frequency (e.g., as shown in  FIG. 3 ), a corresponding transfer function can be estimated. For example, a transfer function representing the coupling factor plot  300  (i.e., a fitted transfer function) can have two poles and two zeros according to the following equation: 
                       H     C   ⁢   F       ⁡     (   s   )       =         A   ⁢     s   2       -     B   ⁢   s     -   C         D   ⁢     s   2       -     E   ⁢   s     -   F               (   6   )               
where s is the Laplace variable: s=jω=j*2π*f, ω is the angular frequency and j the imaginary number. Depending on the application, the transfer function, number of poles and zeros can be changed to achieve the desired performance.
 
     Equation (7) shows simplified fitted transfer function corresponding to the coupling factor variation over frequency of  FIG. 3 : 
     
       
         
           
             
               
                 
                   
                     
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     From the coupling factor transfer function in equation (7), the inverted transfer function (i.e., the transfer function suitable to inversely fit the coupling factor characterization  300  of  FIG. 3 ) can be represented by equation (9) and used to design the compensation filter  84 : 
     
       
         
           
             
               
                 
                   
                     
                       
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     By applying the filtering the magnetic field signal  18  with the filter  84  having the transfer function of equation (8), the sensor output signal  90  can be expressed as follows:
 
 V   OUT ( I )= G·H   CF ( s )· H   Filter ( s )·α(0)· I=G ·α(0)· I   (9)
 
where G represents the gain of the sensor signal path.
 
     As will be appreciated from consideration of equation (9), the resulting sensor output signal V OUT    90  is independent of the current frequency, as is desired. Thus, by determining the transfer function of the coupling factor and applying a filter having an inverse transfer function, dependence of the sensor output signal  90  on the frequency of the current can be eliminated. It will be appreciated that since coupling factor variations over frequency depend on factors such as the conductor design and sensor placement, the coupling factor transfer function (e.g., equation 8) and thus, also the inverted transfer function (e.g., equation 8) will vary according to the application. 
     Referring also to  FIG. 3A  a coupling factor over frequency for an example current sensor system is shown in a plot  360  (that may be the same as or similar to plot  300  of  FIG. 3 ) having a horizontal axis representing the frequency of the current I with a scale in units of Hertz and a vertical axis representing the coupling factor magnitude in decibels. Also shown in  FIG. 3A  is a transfer function  350  for a filter (e.g., filter  84 ) having an inverse relationship with respect to the coupling factor  360  and thus, suitable to cancel the current frequency effects when applied to the magnetic field signal. 
     Referring to  FIG. 3B , the result of the above-described filtering of the magnetic field signal is shown in a plot  370  having a horizontal axis representing the frequency of the current I with a scale in units of Hertz and a vertical axis representing the coupling factor magnitude in decibels. This plot  370  thus represents the current sensor output gain over frequency. As will be appreciated by consideration of  FIG. 3A , the attenuation of the coupling factor over frequency is almost entirely compensated by the above-described filtering. 
     Referring to  FIG. 4 , an example current sensor  400  as may implement the above-described frequency effect compensation (i.e., as may provide the current sensor  12  of  FIG. 1, 52  of  FIG. 1A , or  80  of  FIG. 1B ) illustrates possible current sensor features. Current sensor  400  is a programmable linear sensor having a fault detection module  402 . The current sensor  400  has an analog output voltage VOUT  414  that is proportional to a sensed magnetic field, as may be generated by a current through a conductor (not shown in  FIG. 4 ) external to the sensor  400 . Sensor  400  can be provided in the form of an integrated circuit and includes a magnetic field sensing element, such as a Hall element  404 , to sense the magnetic field. A dynamic offset cancellation module  406  can be used in conjunction with a signal recovery module  408  to chop and then recover the magnetic field signal information in order to thereby reduce offset that can be associated with the magnetic field sensing element  404  for example. Sensitivity control  410  and and offset control  412  can be used (with respective amplifiers  420 ,  422 ) to further adjust the magnetic field signal, as described for example, in U.S. Pat. No. 7,923,996, which is incorporated herein by reference. 
     It will be appreciated that the above-described current frequency compensation can be implemented by introducing the compensation factor through a gain of amplifier  420  and/or  422 . In other words, amplifier  420  and/or  422  can provide the gain element  60  of  FIG. 1A . Alternatively, an additional filter can be used to implement the inverse frequency response associated with a characterized coupling factor as described above in connection with  FIGS. 1B, 3, 3A, and 3B . The result is a current sensor output signal  414  that is substantially independent of a frequency of the sensed conductor current. 
     Referring also to  FIG. 5 , another example current sensor system  500  includes a current sensor  504  as may implement the above-described frequency effect compensation (i.e., as may provide the current sensor  12  of  FIG. 1, 52  of  FIG. 1A , or  80  of  FIG. 1B ) illustrates possible current sensor features. The current sensor  500  provides an output voltage VOUT  548  that is proportional to a sensed magnetic field, as may be generated by a current through a conductor  506  and thus, that is indicative of the current through the conductor. In embodiments, current sensor  500  can be provided in the form of an integrated circuit and the conductor  506  can be internal to the integrated circuit package or can be external to the package. 
     Current sensor  504  includes a magnetic field sensing element  505  and a controller circuit  532 . Controller circuit  532  can generate various control signals to control processing the output signal received from magnetic field sensing element  505 . For example, controller circuit  532  can provide linearly interpolated temperature compensation, and provide greater accuracy in sensitivity and offset voltage trimming and zero drift temperature drift to reduce a total error of current sensor  504  across the respective operating temperature range. 
     Controller circuit  532  can include or be coupled to a fine sensitivity and offset trim circuit  512  and a coarse sensitivity trim circuit  524 . Each of the circuits  512 ,  524  can be controlled to modify an output of current sensor  504  to generate an output signal having high accuracy and compensate for changes in sensor performance due to temperature and other factors. For example, controller circuit  532  can be configured to provide temperature compensation within a predetermined accuracy threshold across the temperature operating range of the current sensor  504 . Further, controller circuit  532  can reduce the sensitivity and offset drift of the magnetic field sensing element  505 . 
     In the example current sensor  504 , magnetic field sensing element  505  is provided as a magnetoresistance element having four resistive elements in a bridge configuration, such as a Wheatstone bridge. For example, magnetoresistance elements  505  may be coupled such that each leg of the bridge includes two elements positioned adjacent to one another, with one such leg spaced from the other leg. With this arrangement, a differential output signal of the bridge (taken between intermediate nodes of each bridge leg) is indicative of the difference between the magnetic field sensed by each bridge leg and results in a differential signal that rejects stray fields from sources other than the current through the conductor  506 . The current sensor  504  can have a voltage source terminal  544  and ground terminal  550  through which power can be supplied to the sensor. 
     More generally, this configuration provides at least one first magnetic field sensing element spaced from at least one second magnetic field sensing element, wherein the at least one first magnetic field sensing element generates at least one first magnetic field signal indicative of a distance between the at least one first magnetic field sensing element and the conductor  506  and the at least one second magnetic field sensing element generates at least one second magnetic field signal indicative of a distance between the at least one second magnetic field sensing element and the conductor. The current sensor circuitry generates a difference signal indicative of a difference between the at least one first magnetic field signal and the at least one second magnetic field signal, which difference signal is indicative of the magnitude of the current. 
     Magnetic field sensing element  505  can generate a magnetic field signal and provide the magnetic field signal to a first amplifier  510  for further coupling to a second amplifier  514 . One or more outputs of second amplifier  514  are coupled to differential amplifier circuit  518 . Differential amplifier circuit  518  can include multiple field effect transistors coupled together to compare two input signals and remove or reduce noise and/or interference (e.g., DC offset) and in some embodiments, apply a gain to the difference between the two input signals. 
     Differential amplifier circuit  518  can be coupled to an inductive feedback element  508  and to a sense element  520 . The inductive feedback element (i.e., a feedback conductor)  508  can be positioned proximate to magnetic field sensing element  505  in order to apply an equal and opposite field (i.e., a feedback field) to the sensing element  505  to thereby implement a closed loop current sensing system. More particularly, with the sense resistor  520 , the feedback current can be sensed and used to generate the sensor output signal  548  that is indicative of the magnitude of the current through conductor  506 . 
     An output of differential amplifier circuit  518  is coupled to a third amplifier  522 . Fine sensitivity and offset trim circuit  512  can be coupled to third amplifier  522 . Fine sensitivity and offset trim circuit  512  can generate and provide a sensitivity trim signal to third amplifier  522  to adjust a sensitivity and/or an offset voltage of third amplifier  522 . One or more outputs of third amplifier  522  can be coupled to one or more inputs of a fourth amplifier  526 . 
     Coarse sensitivity trim circuit  524  can be coupled to fourth amplifier  526 . Coarse sensitivity trim circuit  524  can generate and provide a coarse sensitivity trim signal to fourth amplifier  526  to adjust a sensitivity of fourth amplifier  526 . In embodiments, sensitivity and offset trim can be user programmable. 
     An output of the fourth amplifier  526  can be coupled to a signal conditioning circuit  530 , as shown, in order to generate a fault output signal of the sensor and also to a fifth amplifier  528 . More particularly, once conditioned, the signal can be compared to threshold voltages by a window comparison circuit  534 . The result of the window comparison can be provided to the controller  532  and an over current fault output signal can be generated and provided to a fault terminal  546  (e.g., FAULT pin) of current sensor  504  through an output driver  538 . In embodiments, independent positive and negative over current fault thresholds can be user programmed. An output of fifth amplifier  528  can be coupled to an output terminal  548  of current sensor circuit  504  (e.g., VOUT). 
     It will be appreciated that the above-described current frequency compensation can be implemented by introducing the compensation factor through a gain of one or more of the signal path amplifiers  510 ,  514 ,  522 ,  526 ,  528 . In other words, one or more of these amplifiers can provide the gain element  60  of  FIG. 1A . Alternatively, an additional filter can be used to implement the inverse frequency response associated with a characterized coupling factor as described above in connection with  FIGS. 1B, 3, 3A, and 3B . The result is a current sensor output signal  548  that is substantially independent of a frequency of the sensed conductor current. 
     As described above and will be appreciated by one of skill in the art, embodiments of the disclosure herein may be configured as a system, method, or combination thereof. Accordingly, embodiments of the present disclosure may be comprised of various means including hardware, software, firmware or any combination thereof. Furthermore, embodiments of the present disclosure may take the form of a computer program product on a computer-readable storage medium having computer readable program instructions (e.g., computer software) embodied in the storage medium. Any suitable non-transitory computer-readable storage medium may be utilized. 
     All references cited herein are hereby incorporated herein by reference in their entirety. 
     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. 
     Having described preferred embodiments, it will now become apparent to one of ordinary skill in the art that other embodiments incorporating their concepts 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. 
     It is felt therefore that these embodiments should not be limited to disclosed embodiments, but rather should be limited only by the spirit and scope of the appended claims.