Magnetoresistive sensor with stray field cancellation and systems incorporating same

A system comprising:

• a first magnetic sense element for detecting an external magnetic field along a sensing axis;
• a first magnetic field source proximate the first magnetic sense element for providing an auxiliary magnetic field along the sensing axis of the first magnetic sense element, wherein the first magnetic sense element produces a first output signal having a first magnetic field signal component responsive to the external magnetic field, the first magnetic field signal component being modulated by an auxiliary magnetic field signal component responsive to the auxiliary magnetic field
• a second magnetic sense element for detecting the external magnetic field along the sensing axis;
• the first magnetic source or a second magnetic field source proximate the second magnetic sense element for providing the auxiliary magnetic field along the sensing axis of the second magnetic sense element, wherein:
• the second magnetic sense element produces a third output signal having a second magnetic field signal component responsive to the external magnetic field, the second magnetic field signal component being modulated by the auxiliary magnetic field signal component;
• and
• a processing circuit coupled with the first magnetic sense element, wherein the processing circuit is configured to receive the first output signal, identify from the first output signal an influence of a magnetic interference field on the first auxiliary magnetic field signal component, the magnetic interference field being directed along a non-sensing axis of the first magnetic sense element, and the processing circuit being further configured to apply a correction factor to the magnetic field signal component of the first output signal to produce a second output signal in which an influence of the magnetic interference field is substantially removed from the magnetic field signal component, and wherein the processing circuit is further coupled with the second magnetic sense element and is configured to receive the third output signal, identify from the third output signal the influence of the magnetic interference field on the auxiliary magnetic field signal component, and apply the correction factor to the third output signal to produce a fourth output signal indicative of the second magnetic field signal component in which an influence of the magnetic interference field is substantially removed from the second magnetic field signal component.

In a system that includes a magnetic sense element for detecting an external magnetic field along a sensing axis, the external magnetic field exhibiting a first frequency, a method comprising:

• energizing a magnetic field source located proximate the magnetic sense element to generate an auxiliary magnetic field along the sensing axis of the magnetic sense element, wherein the energizing operation comprises providing a periodic time varying current through the magnetic field source to yield the auxiliary magnetic field as a time varying auxiliary magnetic field at a second frequency that is greater than the first frequency, and wherein the magnetic sense element produces a first output signal having a magnetic field signal component responsive to the external magnetic field, the magnetic field signal component being modulated by an auxiliary magnetic field signal component responsive to the auxiliary magnetic field;
• receiving, at a processing circuit, the first output signal;
• identifying from the first output signal an influence of a magnetic interference field on the auxiliary magnetic field signal component, the magnetic interference field being directed along a non-sensing axis of the magnetic sense element;
• separating, at the processing circuit, the auxiliary magnetic field signal component from the magnetic field signal component in response to the first and second frequencies of the external magnetic field and the auxiliary magnetic field, respectively;
• computing a quotient value as a ratio of a first signal magnitude of the auxiliary magnetic field signal component and a second signal magnitude, wherein the first signal magnitude is influenced by the magnetic interference field and the second signal magnitude is an expected value of the first signal magnitude without the magnetic interference field;
• utilizing the quotient value to determine a correction factor;
• and
• applying the correction factor to the magnetic field signal component of the first output signal to produce a second output signal in which the influence of the magnetic interference field is substantially removed.

A system comprising:

• a magnetoresistive sense element for detecting an external magnetic field along a sensing axis, the external magnetic field exhibiting a first frequency;
• an electrically conductive coil structure proximate the magnetic sense element for providing an auxiliary magnetic field along the sensing axis of the magnetic sense element, the auxiliary magnetic field exhibiting a second frequency that is greater than the first frequency, wherein the magnetoresistive sense element produces a first output signal having a magnetic field signal component responsive to the external magnetic field, the magnetic field signal component being modulated by an auxiliary magnetic field signal component responsive to the auxiliary magnetic field;
• and
• a processing circuit coupled with the magnetic sense element, wherein the processing circuit is configured to:
• receive the first output signal and separate the auxiliary magnetic field signal component from the magnetic field signal component in response to the first and second frequencies of the external magnetic field and the auxiliary magnetic field, respectively;
• compute a quotient value as a ratio of a first signal magnitude of the auxiliary magnetic field signal component and a second signal magnitude of the auxiliary magnetic field signal component, wherein the first signal magnitude is influenced by a magnetic interference field and the second signal magnitude is an expected value of the first signal magnitude without the magnetic interference field, the magnetic interference field being directed along a non-sensing axis of the magnetoresistive sense element;
• utilize the quotient value to determine a correction factor;
• and
• apply the correction factor to the magnetic field signal component of the first output signal to produce a second output signal in which an influence of the magnetic interference field is substantially removed from the magnetic field signal component.