Off-center angle measurement system

An integrated circuit for measuring an angular position of a rotating magnet field at a radially off-center position from an axis of rotation of the magnetic field, the integrated circuit comprising:

• a first set of magnetoresistive elements and an associated first plurality of switches which can be operated to selectively interconnect different subsets of the first set of magnetoresistive elements to form a first sensing bridge at different positions within the integrated circuit, the first sensing bridge configured to provide a first signal representative of a first directional component of the magnetic field;
• and
• a second set of magnetoresistive elements and an associated second plurality of switches which can be operated to selectively interconnect different subsets of the second set of magnetoresistive elements to form a second sensing bridge at different positions within the integrated circuit, the second sensing bridge configured to provide a second signal representative of a second directional component of the magnetic field;
• wherein switches of the first and second pluralities of switches are operated such that the resulting first and second bridges are at positions within the integrated circuit that minimize errors in the first and second signals resulting from non-uniformity of the magnetic field at the radially off-center position.

A method for off-center measurement of an angular position of a rotating shaft, comprising:

• providing a magnetic field which rotates with the shaft about an axis of rotation;
• positioning an integrated circuit having first and second magnetoresistive sensing bridges within the magnetic field at a radially off-center position from the axis of rotation, the first and second magnetoresistive sensing bridges respectively providing first and second signals representative of first and second magnetic field directions, the integrated circuit having a set of adjustment parameters for modifying attributes of the first and second signals;
• modifying values of the set of adjustment parameters until errors in the first and second signals are substantially minimized;
• and
• determining an angular position of the shaft based on the first and second signals.

A method of calibrating an integrated circuit magnetoresistive angle sensor for measuring an angular position of a rotating shaft, the method comprising:

• temporarily coupling a discrete angle sensor to the rotating shaft;
• providing a test signal representative of the angular position of the rotating shaft via the discrete angle sensor;
• positioning the integrated circuit in a magnetic field rotating with the rotating shaft at a radially off-center location from a rotational axis of the rotating shaft, the integrated circuit including a first and a second magnetoresistive sensing bridge respectively providing first and second signals representative of orthogonal first and second directional components of the magnetic field, and including a set of adjustment parameters for modifying attributes of the first and second signals;
• determining a measured angular position of the rotating shaft from the first and second signals;
• adjusting values of the set of parameters to modify attributes of the first and second signals until an error between the angular position provide by the test signal and the measured angular position from the integrated circuit is substantially minimized.