Magnetic field sensor

1. An apparatus, comprising:

a rotatable target to generate a sinusoidal signal in a magnetic field sensor, wherein the target includes a plurality of sinusoidal teeth, wherein the magnetic field sensor comprises:

a substrate having a first and second surfaces;

a magnet disposed proximate to the first surface, wherein the magnet includes at least two poles to generate a magnetic field; and

a first bridge structure having a first plurality of magnetic field sensing elements configured to generate a first magnetic field signal indicative of a position of the target and a second plurality of magnetic field sensing elements configured to generate a second magnetic field signal indicative of the position of the target, wherein a first pair of magnetic field sensing elements of the first plurality of magnetic field sensing elements are spaced a first distance from each other and a second pair of magnetic field sensing elements of the second plurality of magnetic field sensing elements are spaced a second, different distance from each other, and

wherein an axis of sensitivity of the first and second pluralities of magnetic field sensing elements is rotated at a predetermined angle with respect to an axis of rotation of the target, and wherein the first bridge structure is configured to generate an output signal based on the first magnetic field signal and the second magnetic field signal, the output signal corresponding to the position of the target and a change in a property of the magnetic field generated by the magnet.

2. The apparatus according to claim 1 , wherein the target comprises a profile defined as follows:

R

⁡

(

θ

)

=

R

0

+

δ

⁢

R

2

×

[

1

-

cos

⁡

(

n

⁢

θ

)

]

where:

R 0 is the outer radius of the target;

δR is the valley depth;

n is the number of teeth; and

θ is the angle of the target in a range of 0 degrees to 360 degrees.

3. The apparatus according to claim 1 , wherein first and second magnetic field sensing elements of the first plurality of magnetic field sensing elements are spaced equidistant from a first center axis of the magnet.

4. The apparatus according to claim 1 , wherein first and second magnetic field sensing elements of the second plurality of magnetic field sensing elements are spaced equidistant from a first center axis of the magnet.

5. The apparatus according to claim 1 , wherein the first distance between first pair of magnetic field sensing elements of the first plurality of magnetic field sensing elements is less than the second distance between second pair of magnetic field sensing elements of the second plurality of magnetic field sensing elements.

6. An apparatus, comprising:

a rotatable target to generate a sinusoidal signal in a magnetic field sensor, wherein the target includes a plurality of sinusoidal teeth and a number of harmonics to reduce angular error,

wherein the target comprises a profile defined as follows:

R

⁡

(

θ

)

=

R

0

+

∑

h

=

0

N

δ

⁢

R

h

2

×

[

1

-

cos

⁡

(

n

⁡

(

h

+

1

)

⁢

θ

)

]

-

max

⁡

(

∑

h

=

0

N

δ

⁢

R

h

2

×

[

1

-

cos

⁡

(

n

⁡

(

h

+

1

)

⁢

θ

)

]

)

where,

R 0 is the outer radius of the target;

δR is the valley depth;

n is the number of teeth;

θ is the angle;

h is the harmonic index; and

Rh is the amplitude of the h-th harmonic,

wherein the magnetic field sensor comprises:

a substrate having a first and second surfaces;

a magnet disposed proximate to the first surface, wherein the magnet includes at least two poles to generate a magnetic field; and

a first bridge structure having a first plurality of magnetic field sensing elements configured to generate a first magnetic field signal indicative of a position of the target and a second plurality of magnetic field sensing elements configured to generate a second magnetic field signal indicative of the position of the target, wherein a first pair of magnetic field sensing elements of the first plurality of magnetic field sensing elements are spaced a first distance from each other and a second pair of magnetic field sensing elements of the second plurality of magnetic field sensing elements are spaced a second, different distance from each other, and

wherein an axis of sensitivity of the first and second pluralities of magnetic field sensing elements is rotated at a predetermined angle with respect to an axis of rotation of the target, and wherein the first bridge structure is configured to generate an output signal based on the first magnetic field signal and the second magnetic field signal, the output signal corresponding to the position of the target and a change in a property of the magnetic field generated by the magnet.

7. The apparatus according to claim 6 , wherein the number of the harmonics corresponds to the number of shapes on the target.

8. The apparatus according to claim 6 , wherein first and second magnetic field sensing elements of the first plurality of magnetic field sensing elements are spaced equidistant from a first center axis of the magnet.

9. The apparatus according to claim 6 , wherein first and second magnetic field sensing elements of the second plurality of magnetic field sensing elements are spaced equidistant from a first center axis of the magnet.

10. The apparatus according to claim 6 , wherein the first distance between first pair of magnetic field sensing elements of the first plurality of magnetic field sensing elements is less than the second distance between second pair of magnetic field sensing elements of the second plurality of magnetic field sensing elements.

11. A method, comprising:

employing a rotatable target to generate a sinusoidal signal in a magnetic field sensor, wherein the target includes a plurality of sinusoidal teeth, wherein the magnetic field sensor comprises:

a substrate having a first and second surfaces;

a magnet disposed proximate to the first surface, wherein the magnet includes at least two poles to generate a magnetic field; and

a first bridge structure having a first plurality of magnetic field sensing elements configured to generate a first magnetic field signal indicative of a position of the target and a second plurality of magnetic field sensing elements configured to generate a second magnetic field signal indicative of the position of the target, wherein a first pair of magnetic field sensing elements of the first plurality of magnetic field sensing elements are spaced a first distance from each other and a second pair of magnetic field sensing elements of the second plurality of magnetic field sensing elements are spaced a second, different distance from each other, and

wherein an axis of sensitivity of the first and second pluralities of magnetic field sensing elements is rotated at a predetermined angle with respect to an axis of rotation of the target, and wherein the first bridge structure is configured to generate an output signal based on the first magnetic field signal and the second magnetic field signal, the output signal corresponding to the position of the target and a change in a property of the magnetic field generated by the magnet.

12. The method according to claim 11 , wherein the target comprises a profile defined as follows:

R

⁡

(

θ

)

=

R

0

+

δ

⁢

R

2

×

[

1

-

cos

⁡

(

n

⁢

θ

)

]

where:

R 0 is the outer radius of the target;

δR is the valley depth;

n is the number of teeth; and

θ is the angle of the target in a range of 0 degrees to 360 degrees.

13. The method according to claim 11 , wherein first and second magnetic field sensing elements of the first plurality of magnetic field sensing elements are spaced equidistant from a first center axis of the magnet.

14. The method according to claim 11 , wherein first and second magnetic field sensing elements of the second plurality of magnetic field sensing elements are spaced equidistant from a first center axis of the magnet.

15. The method according to claim 11 , wherein the first distance between first pair of magnetic field sensing elements of the first plurality of magnetic field sensing elements is less than the second distance between second pair of magnetic field sensing elements of the second plurality of magnetic field sensing elements.

16. A method, comprising:

employing a rotatable target to generate a sinusoidal signal in a magnetic field sensor, wherein the target includes a plurality of sinusoidal teeth and a number of harmonics to reduce angular error, wherein the target comprises a profile defined as follows:

R

⁡

(

θ

)

=

R

0

+

∑

h

=

0

N

δ

⁢

R

h

2

×

[

1

-

cos

⁡

(

n

⁡

(

h

+

1

)

⁢

θ

)

]

-

max

⁡

(

∑

h

=

0

N

δ

⁢

R

h

2

×

[

1

-

cos

⁡

(

n

⁡

(

h

+

1

)

⁢

θ

)

]

)

where,

R 0 is the outer radius of the target;

δR is the valley depth;

n is the number of teeth;

θ is the angle;

h is the harmonic index; and

Rh is the amplitude of the h-th harmonic,

wherein the magnetic field sensor comprises:

a substrate having a first and second surfaces;

a magnet disposed proximate to the first surface, wherein the magnet includes at least two poles to generate a magnetic field; and

a first bridge structure having a first plurality of magnetic field sensing elements configured to generate a first magnetic field signal indicative of a position of the target and a second plurality of magnetic field sensing elements configured to generate a second magnetic field signal indicative of the position of the target, wherein a first pair of magnetic field sensing elements of the first plurality of magnetic field sensing elements are spaced a first distance from each other and a second pair of magnetic field sensing elements of the second plurality of magnetic field sensing elements are spaced a second, different distance from each other, and

wherein an axis of sensitivity of the first and second pluralities of magnetic field sensing elements is rotated at a predetermined angle with respect to an axis of rotation of the target, and wherein the first bridge structure is configured to generate an output signal based on the first magnetic field signal and the second magnetic field signal, the output signal corresponding to the position of the target and a change in a property of the magnetic field generated by the magnet.

17. The method according to claim 16 , wherein the number of the harmonics corresponds to the number of shapes on the target.

18. A method, comprising:

fabricating a target for a magnetic field sensor, wherein the target comprises a profile defined as follows:

R

⁡

(

θ

)

=

R

0

+

δ

⁢

R

2

×

[

1

-

cos

⁡

(

n

⁢

θ

)

]

where:

R 0 is the outer radius of the target;

δR is the valley depth;

n is the number of teeth; and

θ is the angle of the target in a range of 0 degrees to 360 degrees,

wherein the magnetic field sensor comprises:

a substrate having a first and second surfaces;

a magnet disposed proximate to the first surface, wherein the magnet includes at least two poles to generate a magnetic field; and

a first bridge structure having a first plurality of magnetic field sensing elements configured to generate a first magnetic field signal indicative of a position of the target and a second plurality of magnetic field sensing elements configured to generate a second magnetic field signal indicative of the position of the target, wherein a first pair of magnetic field sensing elements of the first plurality of magnetic field sensing elements are spaced a first distance from each other and a second pair of magnetic field sensing elements of the second plurality of magnetic field sensing elements are spaced a second, different distance from each other, and

wherein an axis of sensitivity of the first and second pluralities of magnetic field sensing elements is rotated at a predetermined angle with respect to an axis of rotation of the target, and wherein the first bridge structure is configured to generate an output signal based on the first magnetic field signal and the second magnetic field signal, the output signal corresponding to the position of the target and a change in a property of the magnetic field generated by the magnet.