Reducing stray magnetic field effect on an angle sensor
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.
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 . 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 . 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 . The angle sensor of claim 1 , wherein the first and second linear sensors are two-dimensional (2-D) sensors.
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 . The angle sensor of claim 5 , wherein the spacer separates the first die from the second die by about 25 microns.
7 . The angle sensor of claim 1 , further comprising a printed circuit board (PCB) electrically connected to the first die by a wire.
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 . The angle sensor of claim 1 , wherein the first linear sensor and the second linear sensor are spaced apart by about 1 millimeter.
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 . The angle sensor of claim 10 , wherein the spacer separates the first die from the second die by about 25 microns.
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 . The angle sensor of claim 10 , wherein the first and second linear sensors are two-dimensional (2-D) sensors.
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 . The angle sensor of claim 10 , wherein the first linear sensor and/or the second linear sensor includes a magnetoresistance element.
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 . 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 . 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 . The angle sensor of claim 18 , wherein the first and second linear sensors are two-dimensional (2-D) sensors.