Circuits and methods for processing signals generated by a circular vertical hall (CVH) sensing element in the presence of a multi-pole magnet
A magnetic field sensor has a circular vertical Hall (CVH) sensing element with a plurality of vertical Hall elements disposed over a common implant region in a substrate. The plurality of vertical Hall elements is disposed in an x-y plane. The magnetic field sensor is responsive to a magnetic field generated by a multi-pole magnet having a plurality of north poles and also a plurality of south poles arranged in a plane parallel to the x-y plane, and, in some embodiments, arranged in the x-y plane. A corresponding method is also described.
1. A magnetic field sensor, comprising:
a semiconductor substrate having a first surface in an x-y plane;
a Circular Vertical Hall (CVH) sensing element comprised of a plurality of vertical Hall elements, wherein each one of the plurality of vertical Hall elements is arranged upon a common circular implant region in the first surface of the semiconductor substrate, wherein the plurality of vertical Hall elements is configured to generate a plurality of x-y output signals responsive to a magnetic field having a direction component parallel to the x-y plane, wherein the CVH sensing element is configured to generate a CVH output signal comprised of the plurality of x-y output signals, wherein the magnetic field results from a multi-pole magnet having a plurality of north poles and a plurality of south poles, each disposed in a plane parallel to the x-y plane, each north pole proximate to at least one south pole;
an angle sensing circuit coupled to receive the CVH output signal and configured to generate an x-y angle signal representative of an angle of the direction component of the magnetic field as the multi-pole magnet and the CVH sensing element move relative to each other;
a pole pair counting module coupled to receive a signal representative of the x-y angle signal and configured to generate a count signal representative of a count of a number of the pole pairs of the multi-pole magnet that move past the CVH sensing element; and
an angle interpolation module coupled to receive the x-y angle signal and the count signal, the angle interpolation module configured to generate a reconstructed x-y angle signal representative of an angular position of the multi-pole magnet relative to the CVH sensing element, the reconstructed x-y angle signal generated based upon the count signal and the x-y angle signal, the reconstructed x-y angle signal having a higher resolution than the x-y angle signal.
2. The magnetic field sensor of claim 1 , wherein the multi-pole magnet comprises a multi-pole ring magnet, and wherein the plurality of north poles and a plurality of south poles are disposed in the x-y plane.
3. The magnetic field sensor of claim 2 , wherein the ring magnet is movably disposed to rotate about an axis perpendicular to the x-y plane.
4. The magnetic field sensor of claim 1 , wherein the multi-pole magnet comprises a multi-pole line magnet, and wherein the plurality of north poles and a plurality of south poles are disposed in the x-y plane.
5. The magnetic field sensor of claim 4 , wherein the line magnet is movably disposed to move along a line in the x-y plane.
6. The magnetic field sensor of claim 4 , wherein the CVH sensing element is movably disposed to move along a line in the x-y plane.
7. The magnetic field sensor of claim 1 , wherein the interpolated signal provides a first resolution of the position of the multi-pole magnet relative to the CVH sensing element, wherein the magnetic field sensor further comprises:
a magnetic field sensing element configured to generate a magnetic field sensing element output signal responsive to a magnetic field generated by a second multi-pole magnet having at least one north pole and at least one south pole;
an electronic circuit coupled to receive the magnetic field sensing element output signal and configured to generate a position signal, wherein the position signal is representative of the position of the second multi-pole magnet relative to the magnetic field sensing element with a second different resolution; and
an output protocol module coupled to receive the interpolated signal and the position signal, and configured to generate an output signal representative of the position signal at some times and configured to generate the output signal representative of the interpolated signal at other times.
8. A method of position sensing, comprising:
generating, with a Circular Vertical Hall (CVH) sensing element, a plurality of x-y output signals responsive to a magnetic field having a direction component parallel to an x-y plane, wherein the CVH sensing element is configured to generate a CVH output signal comprised of the plurality of x-y output signals, wherein the magnetic field result from a multi-pole magnet having a plurality of north poles and a plurality of south poles, each disposed in a plane parallel to the x-y plane, each north pole proximate to at least one south pole;
generating a CVH output signal comprised of the plurality of x-y output signals;
generating an x-y angle signal representative of an angle of the direction component of the magnetic field as the multi-pole magnet and the CVH sensing element move relative to each other;
generating a pole pair count signal representative of a count of a number of the pole pairs of the multi-pole magnet that moves past the CVH sensing element; and
generating a reconstructed x-y angle signal representative of an angular position of the multi-pole magnet relative to the CVH sensing element, the reconstructed x-y angle signal generated based upon the pole pair count signal and the x-y angle signal, the reconstructed x-y angle signal having a higher resolution than the x-y angle signal.
9. The method of claim 8 , wherein the multi-pole magnet comprises a multi-pole ring magnet, and wherein the plurality of north poles and a plurality of south poles are disposed in the x-y plane.
10. The method of claim 9 , wherein the ring magnet is movably disposed to rotate about an axis perpendicular to the x-y plane.
11. The method of claim 8 , wherein the multi-pole magnet comprises a multi-pole line magnet, and wherein the plurality of north poles and a plurality of south poles are disposed in the x-y plane.
12. The method of claim 11 , wherein the line magnet is movably disposed to move along a line in the x-y plane.
13. The method of claim 11 , wherein the CVH sensing element is movably disposed to move along a line in the x-y plane.
14. The method claim 8 , wherein the interpolated signal provides a first resolution of the position of the multi-pole magnet relative to the CVH sensing element, wherein the method further comprises:
generating a magnetic field sensing element output signal responsive to a magnetic field generated by a second multi-pole magnet having at least one north pole and at least one south pole;
generating a position signal is representative of the position of the second multi-pole magnet relative to the magnetic field sensing element with a second different resolution; and
generating an output signal representative of the position signal at some times and generating the output signal representative of the interpolated signal at other times.
15. A magnetic field sensor, comprising:
a Circular Vertical Hall (CVH) sensing element comprised of a plurality of vertical Hall elements, wherein each one of the plurality of vertical Hall elements is arranged upon a common circular implant region in a first surface of a semiconductor substrate, wherein the plurality of vertical Hall elements is configured to generate a plurality of x-y output signals responsive to a magnetic field having a direction component parallel to an x-y plane, wherein the CVH sensing element is configured to generate a CVH output signal comprised of the plurality of x-y output signals;
a clock generator configured to generate a first clock signal and a second clock signal;
an angle sensing circuit coupled to receive the CVH output signal and configured to generate an x-y angle signal representative of an angle of the direction component of the magnetic field, wherein the angle sensing circuit comprises:
a multiplexer coupled to receive the CVH output signal at a first input and coupled to receive the first clock signal at a second input and configured to generate a first multiplexed output signal comprised of the CVH output signal at some times and comprised of the first clock signal at other times;
a comparator coupled to receive a signal representative of the first multiplexed output signal and configured to generate a comparison signal, wherein the comparison signal has state transitions representative of zero crossings of the CVH output signal at some times and state transitions representative of state transitions of the first clock signal at other times;
a counter coupled to receive the comparison signal, coupled to receive a signal representative of the first clock signal, and coupled to receive a signal representative of the second clock signal, wherein the counter is configured to generate a second multiplexed output signal comprised of a first count signal at some times and comprised of a second count signal at other times; and
a combining module coupled to receive a signal representative of the second multiplexed output signal and configured to generate the x-y angle signal as a difference between the first count signal and the second count signal;
a pole pair counting module coupled to receive the x-y angle signal and configured to generate a pole pair count signal representative of a count of a number of the pole pairs of the multi-pole magnet that move past the CVH sensing element; and
an angle interpolation module coupled to receive the x-y angle signal and the pole pair count signal, the angle interpolation module configured to generate a reconstructed x-y angle signal representative of an angular position of the multi-pole magnet relative to the CVH sensing element, the reconstructed x-y angle signal generated based upon the pole pair count signal and the x-y angle signal, the reconstructed x-y angle signal having a higher resolution than the x-y angle signal.
16. A method of position sensing, comprising:
generating, with a Circular Vertical Hall (CVH) sensing element, a plurality of x-y output signals responsive to a magnetic field having a direction component parallel to an x-y plane, wherein the CVH sensing element is configured to generate a CVH output signal comprised of the plurality of x-y output signals;
generating a first clock signal and a second clock signal; and
generating an x-y angle signal representative of an angle of the direction component of the magnetic field, wherein the generating the x-y angle signal comprises:
generating a first multiplexed output signal comprised of the CVH output signal at some times and comprised of the first clock signal at other times;
generating a comparison signal from the first multiplexed output signal, wherein the comparison signal has state transitions representative of zero crossings of the CVH output signal at some times and state transitions representative of state transitions of the first clock signal at other times;
generating a second multiplexed output signal with a counter coupled to receive the comparison signal, coupled to receive a signal representative of the first clock signal, and coupled to receive a signal representative of the second clock signal, wherein the second multiplexed output signal is comprised of a first count signal at some times and comprised of a second count signal at other times; and
generating the x-y angle signal as a difference between the first count signal and the second count signal;
generating a pole pair count signal representative of a count of a number of the pole pairs of the multi-pole magnet that moves past the CVH sensing element; and
generating a reconstructed x-y angle signal representative of an angular position of the multi-pole magnet relative to the CVH sensing element, the reconstructed x-y angle signal generated based upon the pole pair count signal and the x-y angle signal, the reconstructed x-y angle signal having a higher resolution than the x-y angle signal.
17. The magnetic field sensor of claim 1 , wherein the reconstructed x-y angle signal removes an ambiguity from the x-y angle signal of the angular position of the multi-pole magnet relative to the CVH sensing element.
18. The method of claim 8 , wherein generating the reconstructed x-y angle signal comprises removing an ambiguity from the x-y angle signal of the angular position of the multi-pole magnet relative to the CVH sensing element.