US-12618661-B2 - Reducing stray magnetic field effect on an angle sensor

Abstract

In one aspect, an angle sensor includes a first linear sensor and a second linear sensor. A first magnetic-field direction of a target magnet measured by the first linear sensor is substantially equal to a second magnetic-field direction of the target magnet measured by the second linear sensor. The first linear sensor, the second linear sensor and the target magnet are on an axis. The angle sensor determines an angle of a magnetic field.

Inventors

• Rémy Lassalle-Balier
• Jean-Michel Daga

Assignees

• ALLEGRO MICROSYSTEMS, LLC

Dates

Publication Date

20260505

Application Date

20230201

Claims (19)

1. 1 . An angle sensor comprising: a first linear sensor; and a second linear sensor, a first die having a first surface and an opposing second surface, the first linear sensor being disposed on the first surface of the first die; a second die having a first surface and an opposing second surface, the second linear sensor being disposed on the second surface of the second die; wherein a first magnetic-field direction of a target magnet measured by the first linear sensor is substantially equal to a second magnetic-field direction of the target magnet measured by the second linear sensor, wherein the first linear sensor, the second linear sensor and the target magnet are on an axis, wherein the angle sensor determines an angle of a magnetic field by: detecting an amplitude and direction of a magnetic field at the first linear sensor and the second linear sensor; and calculating a difference between the magnetic field detected at the first linear sensor and the second linear sensor; and wherein the first linear sensor and the second linear sensor have a linear range equal to a maximum field range from the target magnet plus twice a maximum amplitude of a stray magnetic field, such that the first and second linear sensor each remain within a linear region, allowing the first linear sensor and the second linear sensor to avoid a saturation region.
2. 2 . The angle sensor of claim 1 , wherein the first linear sensor is disposed along a first plane and the second linear sensor is disposed along a second plane; and wherein the first plane and the second plane are each perpendicular to the axis.
3. 3 . The angle sensor of claim 2 , wherein the target magnet is disposed along a third plane and the third plane is perpendicular to the axis.
4. 4 . The angle sensor of claim 1 , wherein the first and second linear sensors are two-dimensional (2-D) sensors.
5. 5 . The angle sensor of claim 1 , further comprising a spacer layer in direct contact with the second surface of the first die and the first surface of the second die.
6. 6 . The angle sensor of claim 5 , wherein the spacer separates the first die from the second die by about 25 microns.
7. 7 . The angle sensor of claim 1 , further comprising a printed circuit board (PCB) electrically connected to the first die by a wire.
8. 8 . The angle sensor of claim 7 , wherein the second die is disposed in a flip-chip structure having solder balls in direct contact with the PCB.
9. 9 . The angle sensor of claim 1 , wherein the first linear sensor and the second linear sensor are spaced apart by about 1 millimeter.
10. 10 . An angle sensor comprising: a first linear sensor; a second linear sensor; a first die having a first surface and an opposing second surface, the first linear sensor being disposed on the first surface of the first die; a second die having a first surface and an opposing second surface, the second linear sensor being disposed on the second surface of the second die; a spacer layer in direct contact with the second surface of the first die and the first surface of the second die; and a printed circuit board (PCB) electrically connected to the first die by a wire, wherein a first magnetic-field direction of a target magnet measured by the first linear sensor is substantially equal to a second magnetic-field direction of the target magnet measured by the second linear sensor, wherein the first linear sensor, the second linear sensor and the target magnet are on an axis, and wherein the angle sensor determines an angle of a magnetic field by: detecting an amplitude and direction of a magnetic field at the first linear sensor and the second linear sensor; and calculating a difference between the magnetic field detected at the first linear sensor and the second linear sensor, and wherein the first linear sensor and the second linear sensor have a linear range equal to a maximum field range from the target magnet plus twice a maximum amplitude of a stray magnetic field, such that the first and second linear sensor each remain within a linear region, allowing the first linear sensor and the second linear sensor to avoid a saturation region.
11. 11 . The angle sensor of claim 10 , wherein the spacer separates the first die from the second die by about 25 microns.
12. 12 . The angle sensor of claim 10 , wherein the second die is disposed in a flip-chip structure having solder balls in direct contact with the PCB.
13. 13 . The angle sensor of claim 10 , wherein the first and second linear sensors are two-dimensional (2-D) sensors.
14. 14 . The angle sensor of claim 10 , wherein the first linear sensor and the second linear sensor are spaced apart by about 1 millimeter.
15. 15 . The angle sensor of claim 10 , wherein the first linear sensor and/or the second linear sensor includes a magnetoresistance element.
16. 16 . An angle sensor comprising: a first linear sensor; and a second linear sensor, a first die having a first surface and an opposing second surface, the first linear sensor being disposed on the first surface of the first die; a second die having a first surface and an opposing second surface, the second linear sensor being disposed on the second surface of the second die; wherein a first magnetic-field direction of a target magnet measured by the first linear sensor is substantially equal to a second magnetic-field direction of the target magnet measured by the second linear sensor, wherein the first linear sensor, the second linear sensor and the target magnet are on an axis, wherein the angle sensor determines an angle of a magnetic field by: detecting an amplitude and direction of a magnetic field at the first linear sensor and the second linear sensor; and calculating a difference between the magnetic field detected at the first linear sensor and the second linear sensor; and wherein the first linear sensor and the second linear sensor have a linear range equal to a maximum field range from the target magnet plus twice a maximum amplitude of a stray magnetic field, such that the first and second linear sensor each remain within a linear region, allowing the first linear sensor and the second linear sensor to avoid a saturation region.
17. 17 . The angle sensor of claim 16 , wherein the first linear sensor is disposed along a first plane and the second linear sensor is disposed along a second plane; and wherein the first plane and the second plane are each perpendicular to the axis.
18. 18 . The angle sensor of claim 17 , wherein the target magnet is disposed along a third plane and the third plane is perpendicular to the axis.
19. 19 . The angle sensor of claim 18 , wherein the first and second linear sensors are two-dimensional (2-D) sensors.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This is a Divisional application and claims the benefit of and priority to U.S. patent application Ser. No. 16/800,229, filed Feb. 25, 2020, entitled “REDUCING STRAY MAGNETIC FIELD EFFECT ON AN ANGLE SENSOR,” which is incorporated herein by reference in its entirety. BACKGROUND Typically, a magnetic-field angle sensor measures a direction of a magnetic-field vector through 360° in an x-y plane. In one example, a magnetic-field angle sensor may be used to detect an angular position of a rotating magnet. The presence of stray magnetic fields (i.e., magnetic fields coming from other sources than a desired target) can increase an angle error of the angle sensor. Generally, the angle error is defined to be the difference between an actual position of a magnet and a position of the magnet as measured by the angle sensor. SUMMARY In one aspect, an angle sensor includes a first linear sensor and a second linear sensor. A first magnetic-field direction of a target magnet measured by the first linear sensor is substantially equal to a second magnetic-field direction of the target magnet measured by the second linear sensor. The first linear sensor, the second linear sensor and the target magnet are on an axis. The angle sensor determines an angle of a magnetic field. In another aspect, an angle sensor configuration includes a first coil, a second coil parallel to the first coil and an angle sensor disposed between the first coil and the second coil. The angle sensor configured to determine an angle of a magnetic field. In a further aspect, an angle sensor configuration includes an angle sensor, a first magnet having a first outward magnetized pole along a first axis away from the angle sensor and a second magnet opposite the first magnetic. The second magnet has a second outward magnetized pole along the first axis away from the angle sensor. The angle sensor configuration further includes a third magnet having a first inward magnetized pole along a second axis toward the angle sensor and a fourth magnet opposite the third magnetic. The third magnet has a second inward magnetized pole along the second axis toward the angle sensor. The angle sensor is disposed between the first, second, third and fourth magnets. The angle sensor configured to determine an angle of a magnetic field. 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 diagram of an example of stacked two-dimensional (2D) linear sensors forming an angle sensor to reduce a stray magnetic field effect; FIG. 2 is a diagram of example of stacked 2D linear sensor package configuration; FIG. 3 is a diagram of an example of magnetic field directions for one of the stacked 2D linear sensors closer to the magnet target; FIG. 4 is a diagram of an example of magnetic field directions for one of the stacked 2D linear sensors further to the magnet target; FIG. 5 is a diagram of an example of magnetic field directions for the 2D stacked linear sensors; FIG. 6 is a diagram of an example of an angle sensor configuration with two cosine coils to reduce a stray magnetic field effect; FIG. 7 is a diagram of an example of a circuit representation of FIG. 6 having two bridges; FIG. 8A is a graph of an example of outputs of the two bridges in FIG. 7; FIG. 8B is a graph of an example of the angle error for the angle sensor configuration of FIG. 6; FIG. 9 is a diagram of another example of an angle sensor configuration with two cosine and two sine coils to reduce a stray magnetic field effect; FIG. 10 is a circuit representation of FIG. 9 having one bridge; FIG. 11 is a diagram of an example of an angle sensor configuration with inward and outward magnetized pole magnets to reduce a stray magnetic field effect; FIG. 12 is a diagram of the inward and outward magnetized pole magnets of FIG. 11 overlaid with an example of a level plot of magnetic field amplitudes; FIG. 13 is a diagram of FIG. 12 with example locations for magnetoresistance elements; FIG. 14A is a diagram of an example of a cosine bridge at locations in FIG. 13; FIG. 14B is a diagram of an example of a sine bridge at locations in FIG. 13; FIG. 15A is a graph of example of outputs for the sine and cosine bridges of FIGS. 14A and 14B; FIG. 15B is a graph of example of Hall signals; FIG. 15C is a graph of an example of an output signal of an angle sensor; FIG. 15D is a graph of an example of an angle error for the angle sensor configuration of FIG. 11; FIG. 16 is a graph of an example o