Methods and apparatus for phase selection in ring magnet sensing
Methods and apparatus for positioning a magnetic field sensor IC package having a first channel for a planar magnetic field sensing element and a second channel for vertical magnetic field sensing element in relation to an axis of a ring magnet to provide a desired phase relationship between the first and second channels. In embodiments, positioning the sensor includes an offset angle and a displacement with respect to a centerline of the ring magnet.
1. A method, comprising:
for a magnetic field sensor IC package having a first channel for a planar magnetic field sensing element and a second channel for a vertical magnetic field sensing element, receiving a desired phase relationship between the first and second channels;
positioning the IC package in relation to an axis of a ring magnet to provide the desired phase relationship between the first and second channels; and
positioning the IC package to a non-zero twist angle with respect to the axis and a non-zero displacement with respect to the axis,
wherein the phase relationship is selected using a mesh function of the offset angle and displacement for the sensor.
2. The method according to claim 1 , wherein the axis corresponds to a centerline of the ring magnet.
3. The method according to claim 2 , wherein the centerline corresponds to one-half a width of the ring magnet.
4. The method according to claim 1 , wherein the desired phase relationship is about 120 degrees.
5. The method according 1 , wherein the desired phase relationship is about 60 degrees.
6. The method according to claim 1 , further including displacing the IC package position a distance from an axis of rotation of the ring magnet.
7. The method according to claim 1 , wherein the IC package has a longitudinal axis defined by being parallel to a sensing direction of the first sensing element, wherein the twist angle is defined by the longitudinal axis of the IC package and a centerline of the ring magnet.
8. The method according to claim 1 , wherein a substantially planar face of the IC package defines an air gap with a surface of the ring magnet.
9. The method according to claim 1 , wherein the planar magnetic field sensing element and the vertical magnetic field sensing element are formed as part of a single die.
10. The method according to claim 1 , wherein the planar magnetic field sensing element and the vertical magnetic field sensing element are substantially collocated.
11. The method according to claim 1 , further including positioning the IC package to lessen sensitivity to mechanical tolerances.
12. The method according to claim 1 , wherein the first sensing element comprises a Hall element.