U.S. patent application number 13/724170 was filed with the patent office on 2014-06-26 for magnetic field sensor and method of fabricating a magnetic field sensor having a plurality of vertical hall elements arranged in at least a portion of a polygonal shape.
The applicant listed for this patent is Andrea Foletto, Andreas P. Friedrich, Nicolas Yoakim. Invention is credited to Andrea Foletto, Andreas P. Friedrich, Nicolas Yoakim.
Application Number | 20140175584 13/724170 |
Document ID | / |
Family ID | 49726889 |
Filed Date | 2014-06-26 |
United States Patent
Application |
20140175584 |
Kind Code |
A1 |
Foletto; Andrea ; et
al. |
June 26, 2014 |
MAGNETIC FIELD SENSOR AND METHOD OF FABRICATING A MAGNETIC FIELD
SENSOR HAVING A PLURALITY OF VERTICAL HALL ELEMENTS ARRANGED IN AT
LEAST A PORTION OF A POLYGONAL SHAPE
Abstract
A magnetic field sensor has a plurality of vertical Hall
elements arranged in at least a portion of a polygonal shape. The
magnetic field sensor includes an electronic circuit to process
signals generated by the plurality of vertical Hall elements to
identify a direction of a magnetic field. A corresponding method of
fabricating the magnetic field sensor is also described.
Inventors: |
Foletto; Andrea; (Annecy,
FR) ; Friedrich; Andreas P.; (Metz-Tessy, FR)
; Yoakim; Nicolas; (Annecy, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Foletto; Andrea
Friedrich; Andreas P.
Yoakim; Nicolas |
Annecy
Metz-Tessy
Annecy |
|
FR
FR
FR |
|
|
Family ID: |
49726889 |
Appl. No.: |
13/724170 |
Filed: |
December 21, 2012 |
Current U.S.
Class: |
257/427 ;
438/48 |
Current CPC
Class: |
G01R 33/0023 20130101;
H01L 29/82 20130101; G01R 33/077 20130101 |
Class at
Publication: |
257/427 ;
438/48 |
International
Class: |
G01B 7/30 20060101
G01B007/30; H01L 29/82 20060101 H01L029/82 |
Claims
1. A magnetic field sensor, comprising: a semiconductor substrate
having a planar surface; a plurality of primary vertical Hall
elements disposed on the planar surface, wherein each one of the
plurality of primary vertical Hall elements comprises a respective
plurality of primary vertical Hall element contacts arranged in a
respective line, wherein the lines of primary vertical Hall element
contacts are arranged in a pattern representative of at least a
portion of a polygonal shape, wherein the plurality of primary
vertical Hall elements includes a primary vertical Hall element
having a respective line of vertical Hall element contacts not
parallel to a line of vertical Hall element contacts of another one
of the plurality of primary vertical Hall elements, wherein each
one of the plurality of primary vertical Hall elements is
configured to generate a respective magnetic field signal
indicative of a projected component of a magnetic field projected
upon the plane of the planar surface relative to an angular
position of the respective vertical Hall element; and an electronic
circuit disposed on the planar surface and coupled to each one of
the plurality of primary vertical Hall elements, wherein the
electronic circuit is configured to generate an output signal
indicative of an angle of the projected component of the magnetic
field.
2. The magnetic field sensor of claim 1, wherein the plurality of
primary vertical Hall elements comprises a common primary implant
region in the planar surface of the substrate.
3. The magnetic field sensor of claim 1, wherein the plurality of
primary vertical Hall elements comprises separate primary implant
regions in the planar surface of the substrate and does not
comprise a common primary implant region in the planar surface of
the substrate.
4. The magnetic field sensor of claim 1, wherein the lines of the
primary vertical Hall element contacts are arranged in straight
lines and in a pattern representative of a polygonal shape.
5. The magnetic field sensor of claim 1, wherein the lines of the
primary vertical Hall element contacts are arranged in straight
lines and in a pattern representative of half of a polygonal
shape.
6. The magnetic field sensor of claim 5, wherein the electronic
circuit is further configured to use the plurality of primary
vertical Hall elements to generate magnetic field signals
representative of an entire polygonal shape.
7. The magnetic field sensor of claim 1, further comprising: a
plurality of secondary vertical Hall elements disposed on the
planar surface, wherein each one of the secondary vertical Hall
elements comprises a respective plurality of secondary vertical
Hall element contacts arranged in a respective line, wherein each
one of the plurality of secondary vertical Hall elements is
arranged in a respective group with a respective one of the
plurality of primary vertical Hall elements, wherein each line of
secondary vertical Hall element contacts is geometrically arranged
at a predetermined angle with a respective line of primary vertical
Hall element contacts to form a plurality of parallel groups of
vertical Hall elements.
8. The magnetic field sensor of claim 7, wherein the lines of
primary vertical Hall element contacts are arranged in straight
lines and in a pattern representative of a polygonal shape.
9. The magnetic field sensor of claim 7, wherein the lines of
primary vertical Hall element contacts are arranged in straight
lines and in a pattern representative of half of a polygonal
shape.
10. The magnetic field sensor of claim 9, wherein the electronic
circuit is further configured to use the plurality of primary and
secondary vertical Hall elements to generate magnetic field signals
representative of an entire polygonal shape.
11. The magnetic field sensor of claim 7, wherein the plurality of
secondary vertical Hall elements comprises a common secondary
implant region in the planar surface of the substrate.
12. The magnetic field sensor of claim 7, wherein the plurality of
secondary vertical Hall elements comprises separate secondary
implant regions in the planar surface of the substrate and do not
comprise a common secondary implant region in the planar surface of
the substrate.
13. The magnetic field sensor of claim 7, wherein respective
magnetic field signals generated by vertical Hall elements of each
one of the plurality of parallel groups of vertical Hall elements
are respectively summed in the electronic circuit.
14. The magnetic field sensor of claim 7, wherein the vertical Hall
elements of each parallel group of vertical Hall elements are
respectively coupled in parallel.
15. The magnetic field sensor of claim 7, wherein no parallel group
of vertical Hall elements has lines of vertical Hall element
contacts that are parallel to lines of vertical Hall element
contacts within another parallel group of vertical Hall
elements.
16. The magnetic field sensor of claim 7, wherein the electronic
circuit comprises: first and second vertical Hall element driving
circuits; and a selection circuit coupled between the first and
second vertical Hall element driving circuits and the plurality of
parallel groups of vertical Hall elements, wherein the selection
circuit is configured to switch couplings between the first and
second vertical Hall element driving circuits and the plurality of
parallel groups of vertical Hall elements, wherein, during a time
when one of the plurality of parallel groups of vertical Hall
elements is being driven by the first vertical Hall element driving
circuit and processed by the electronic circuit, another one of the
plurality of parallel groups of vertical Hall elements is being
driven by the second vertical Hall element driving circuit.
17. The magnetic field sensor of claim 7, wherein the electronic
circuit further comprises a switching circuit coupled to the
plurality of parallel groups of vertical Hall elements and
configured to select from among the plurality of parallel groups of
vertical Hall elements such that selected ones of the plurality of
parallel groups of vertical Hall elements generate respective
magnetic field signals at different times on the same signal
path.
18. The magnetic field sensor of claim 1, wherein the electronic
circuit further comprises: first and second vertical Hall element
driving circuits; and a selection circuit coupled between the first
and second vertical Hall element driving circuits and the plurality
of primary vertical Hall elements, wherein the selection circuit is
configured to switch couplings between the first and second
vertical Hall element driving circuits and the plurality of primary
vertical Hall elements, wherein, during a time when one of the
plurality of primary vertical Hall elements is being driven by the
first vertical Hall element driving circuits and processed by the
electronic circuit, another one of the plurality of primary
vertical Hall elements is being driven by the second vertical Hall
element driving circuit.
19. The magnetic field sensor of claim 1, wherein the electronic
circuit further comprises a switching circuit coupled to the
plurality of primary vertical Hall elements and configured to
select from among the plurality of primary vertical Hall elements
such that selected ones of the plurality of primary vertical Hall
elements generate respective magnetic field signals at different
times on the same signal path.
20. A method of fabricating a magnetic field sensor, comprising:
providing a semiconductor substrate having a planar surface;
forming, on the planar surface, a plurality of primary vertical
Hall elements, wherein each one of the plurality of primary
vertical Hall elements comprises a respective plurality of vertical
Hall element contacts arranged in a respective line of primary
vertical Hall element contacts, wherein the lines of primary
vertical Hall element contacts are arranged in a pattern
representative of at least a portion a polygonal shape, wherein the
plurality of primary vertical Hall elements includes a primary
vertical Hall element having a respective line of vertical Hall
element contacts not parallel to a line of vertical Hall element
contacts of another one of the plurality of primary vertical Hall
elements, wherein each one of the plurality of primary vertical
Hall elements is configured to generate a respective magnetic field
signal indicative of a projected component of a magnetic field
projected upon the plane of the planar surface relative to an
angular position of the respective vertical Hall element; and
forming, on the semiconductor substrate, an electronic circuit
coupled to each one of the plurality of primary vertical Hall
elements, wherein the electronic circuit is configured to generate
an output signal representative of an angle of the projected
component of the magnetic field.
21. The method of claim 20, wherein the forming the plurality of
primary vertical Hall elements comprises forming a common primary
implant region in the planar surface of the substrate.
22. The method of claim 20, wherein the forming the plurality of
primary vertical Hall elements comprises forming separate primary
implant regions in the planar surface of the substrate and not
forming a common primary implant region in the planar surface of
the substrate.
23. The method of claim 20, wherein the lines of primary vertical
Hall element contacts are arranged in straight lines and in a
pattern representative of a polygonal shape.
24. The method of claim 20, wherein the lines of primary vertical
Hall element contacts are arranged in straight lines and in a
pattern representative of half of a polygonal shape.
25. The method of claim 20, further comprising: forming, on the
planar surface, a plurality of secondary vertical Hall elements,
wherein each one of the secondary vertical Hall elements comprises
a respective plurality of secondary vertical Hall element contacts
arranged in a respective line, wherein each one of the plurality of
secondary vertical Hall elements is arranged in a respective group
with a respective one of the plurality of primary vertical Hall
elements, wherein each line of secondary vertical Hall element
contacts is geometrically arranged at a predetermined angle with a
respective line of primary vertical Hall element contacts to form a
plurality of parallel groups of vertical Hall elements.
26. The method of claim 25, wherein the lines of primary vertical
Hall element contacts are arranged in straight lines and in a
pattern representative of a polygonal shape.
27. The method of claim 25, wherein the lines of primary vertical
Hall element contacts are arranged in straight lines and in a
pattern representative of half of a polygonal shape.
28. The method of claim 25, wherein the forming the plurality of
secondary vertical Hall elements comprises forming a common
secondary implant region in the planar surface of the
substrate.
29. The method of claim 25, wherein the forming the plurality of
secondary vertical Hall elements comprises forming separate
secondary implant regions in the planar surface of the substrate
and not forming a common secondary implant region in the planar
surface of the substrate.
30. The method of claim 25, further comprising: respectively
coupling in parallel the vertical Hall elements of each parallel
group of vertical Hall elements.
31. The method of claim 25, wherein no parallel group of vertical
Hall elements has lines of vertical Hall element contacts that are
parallel to lines of vertical Hall element contacts within another
parallel group of vertical Hall elements.
32. The method of claim 25, wherein the forming the electronic
circuit comprises: forming first and second vertical Hall element
driving circuits; and forming a selection circuit coupled between
the first and second vertical Hall element driving circuits and the
plurality of parallel groups of vertical Hall elements, wherein the
selection circuit is configured to switch couplings between the
first and second vertical Hall element driving circuits and the
plurality of parallel groups of vertical Hall elements, wherein,
during a time when one of the plurality of parallel groups of
vertical Hall elements is being driven by the first vertical Hall
element driving circuits and processed by the electronic circuit,
another one of the plurality of parallel groups of vertical Hall
elements is being driven by the second vertical Hall element
driving circuit.
33. The method of claim 25, wherein the forming the electronic
circuit further comprises: forming a switching circuit coupled to
the plurality of parallel groups of vertical Hall elements and
configured to select from among the plurality of parallel groups of
vertical Hall elements such that selected ones of the plurality of
parallel groups of vertical Hall elements generate respective
magnetic field signals at different times on the same signal
path.
34. The method of claim 20, wherein the forming the electronic
circuit comprises: forming first and second vertical Hall element
driving circuits; and forming a selection circuit coupled between
the first and second vertical Hall element driving circuits and the
plurality of primary vertical Hall elements, wherein the selection
circuit is configured to switch couplings between the first and
second vertical Hall element driving circuits and the plurality of
primary vertical Hall elements, wherein, during a time when one of
the plurality of primary vertical Hall elements is being driven by
the first vertical Hall element driving circuits and processed by
the electronic circuit, another one of the plurality of primary
vertical Hall elements is being driven by the second vertical Hall
element driving circuit.
35. The method of claim 20, wherein the forming the electronic
circuit further comprises: forming a switching circuit coupled to
the plurality of primary vertical Hall elements and configured to
select from among the plurality of primary vertical Hall elements
such that selected ones of the plurality of primary vertical Hall
elements generate respective magnetic field signals at different
times on the same signal path.
36. A magnetic field sensor, comprising: a semiconductor substrate
having a planar surface; a plurality of magnetic field sensing
elements disposed on the planar surface, the plurality of magnetic
field sensing elements having a respective plurality of major
response axes, each major response axis parallel to the major
surface, wherein the plurality of major response axes is arranged
in a pattern representative of at least a portion of a polygonal
shape, wherein the plurality of magnetic field sensing elements
includes a primary vertical Hall element having a major response
axis not parallel to major response axis of another one of the
plurality of magnetic field sensing elements, wherein each one of
the plurality of magnetic field sensing elements is configured to
generate a respective magnetic field signal indicative of a
projected component of a magnetic field projected upon the plane of
the planar surface relative to an angular position of the response
axis of the respective magnetic field sensing element; and an
electronic circuit disposed on the planar surface and coupled to
each one of the plurality of magnetic field sensing elements,
wherein the electronic circuit is configured to generate an output
signal indicative of an angle of the projected component of the
magnetic field.
37. The magnetic field sensor of claim 36, wherein the plurality of
magnetic field sensing elements comprises a plurality of
magnetoresistance elements.
38. A method of fabricating a magnetic field sensor, comprising:
providing a semiconductor substrate having a planar surface;
forming, on the planar surface, a plurality of magnetic field
sensing elements having a respective plurality of major response
axes, each major response axis parallel to the major surface,
wherein the plurality of major response axes is arranged in a
pattern representative of at least a portion of a polygonal shape,
wherein the plurality of magnetic field sensing elements includes a
primary vertical Hall element having a major response axis not
parallel to major response axis of another one of the plurality of
magnetic field sensing elements, wherein each one of the plurality
of magnetic field sensing elements is configured to generate a
respective magnetic field signal indicative of a projected
component of a magnetic field projected upon the plane of the
planar surface relative to an angular position of the response axis
of the respective magnetic field sensing element; and forming, on
the semiconductor substrate, an electronic circuit coupled to each
one of the plurality of magnetic field sensing elements, wherein
the electronic circuit is configured to generate an output signal
indicative of an angle of the projected component of the magnetic
field.
39. The method of claim 38, wherein the plurality of magnetic field
sensing elements comprises a plurality of magnetoresistance
elements.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] Not Applicable.
FIELD OF THE INVENTION
[0003] This invention relates generally to magnetic field sensors
and related fabrication techniques, and, more particularly, to a
magnetic field sensor and corresponding fabrication technique
having a plurality of vertical Hall elements arranged in at least a
portion of a polygonal pattern and also having an electronic
circuit coupled to the plurality of vertical Hall elements.
BACKGROUND OF THE INVENTION
[0004] Planar Hall elements and vertical Hall elements are known
types of magnetic field sensing elements that can be used in
magnetic field sensors. A planar Hall element tends to be
responsive to magnetic field perpendicular to a surface of a
substrate on which the planar Hall element is formed. A vertical
Hall element tends to be responsive to magnetic field parallel to a
surface of a substrate on which the vertical Hall element is
formed.
[0005] Other types of magnetic field sensing elements are known.
For example, a so-called "circular vertical Hall" (CVH) sensing
element, which includes a plurality of vertical magnetic field
sensing elements, is known and described in PCT Patent Application
No. PCT/EP2008/056517, entitled "Magnetic Field Sensor for
Measuring Direction of a Magnetic Field in a Plane," filed May 28,
2008, and published in the English language as PCT Publication No.
WO 2008/145662, which application and publication thereof are
incorporated by reference herein in their entirety. The CVH sensing
element is a circular arrangement of vertical Hall elements
arranged over a common circular implant region in a substrate. The
CVH sensing element can be used to sense a direction (and
optionally a strength) of a magnetic field in a plane of the
substrate.
[0006] Conventionally, all of the output signals from the plurality
of vertical Hall elements within the CVH sensing element are needed
in order to determine a direction of a magnetic field. Also
conventionally, output signals from the vertical Hall elements of a
CVH sensing element are generated sequentially, resulting in a
substantial amount of time necessary to generate all of the output
signals from the CVH sensing element. Thus, determination of the
direction of the magnetic field can take a substantial amount of
time.
[0007] Various parameters characterize the performance of magnetic
field sensing elements. These parameters include sensitivity, which
is a change in an output signal of a magnetic field sensing element
in response to a change of magnetic field experienced by the
magnetic sensing element, and linearity, which is a degree to which
the output signal of the magnetic field sensing element varies in
direct proportion to the magnetic field. These parameters also
include an offset, which is characterized by an output signal from
the magnetic field sensing element not representative of a zero
magnetic field when the magnetic field sensing element experiences
a zero magnetic field.
[0008] Another parameter that can characterize the performance of a
CVH sensing element is the speed with which output signals from
vertical Hall elements within the CVH sensing element can be
sampled, and thus, the speed with which a direction of a magnetic
field can be identified. Yet another parameter that can
characterize the performance of a CVH sensing element is the
resolution (e.g., angular step size) of the direction of the
magnetic field that can be reported by the CVH sensing element.
[0009] As described above, the CVH sensing element is operable,
with associated circuits, to provide an output signal
representative of an angle of a direction of a magnetic field.
Therefore, as described below, if a magnet is disposed upon or
otherwise coupled to a so-called "target object," for example, a
camshaft in an engine, the CVH sensing element can be used to
provide an output signal representative of an angle of rotation,
and/or a rotation speed, of the target object.
[0010] For reasons described above, a magnetic field sensor that
uses a CVH sensing element may have a limit as to how rapidly the
magnetic field sensor can identify the direction of a magnetic
field, i.e., a rotation angle or rotation speed of a target object.
Furthermore, the magnetic field sensor may provide an angular
resolution that is too low (too large an angle step size). In
general, it may be possible to provide a higher resolution, but at
the expense of more time.
[0011] Thus, it would be desirable to provide a magnetic field
sensing element (or, more generally, a plurality of magnetic field
sensing elements) that can be used to generate an output signal
more rapidly indicative of an angle of a magnetic field than a CVH
sensing element.
SUMMARY OF THE INVENTION
[0012] The present invention provides a magnetic field sensing
element (or, more generally, a plurality of magnetic field sensing
elements) that can be used to generate an output signal more
rapidly indicative of an angle of a magnetic field than a CVH
sensing element.
[0013] In accordance with one aspect of the present invention, a
magnetic field sensor includes a semiconductor substrate having a
planar surface. The magnetic field sensor also includes a plurality
of primary vertical Hall elements disposed on the planar surface.
Each one of the plurality of primary vertical Hall elements
includes a respective plurality of primary vertical Hall element
contacts arranged in a respective line. The lines of primary
vertical Hall element contacts are arranged in a pattern
representative of at least a portion of a polygonal shape. The
plurality of primary vertical Hall elements includes a primary
vertical Hall element having a respective line of vertical Hall
element contacts not parallel to a line of vertical Hall element
contacts of another one of the plurality of primary vertical Hall
elements. Each one of the plurality of primary vertical Hall
elements is configured to generate a respective magnetic field
signal indicative of a projected component of a magnetic field
projected upon the plane of the planar surface relative to an
angular position of the respective vertical Hall element. The
magnetic field sensor also includes an electronic circuit disposed
on the planar surface and coupled to each one of the plurality of
primary vertical Hall elements. The electronic circuit is
configured to generate an output signal indicative of an angle of
the projected component of the magnetic field.
[0014] In some embodiments, the magnetic field sensor also includes
a plurality of secondary vertical Hall elements disposed on the
planar surface. Each one of the secondary vertical Hall elements
includes a respective plurality of secondary vertical Hall element
contacts arranged in a respective line. Each one of the plurality
of secondary vertical Hall elements is arranged in a respective
group with a respective one of the plurality of primary vertical
Hall elements. Each line of secondary vertical Hall element
contacts is geometrically arranged at a predetermined angle with a
respective line of primary vertical Hall element contacts to form a
plurality of parallel groups of vertical Hall elements.
[0015] In accordance with another aspect of the present invention,
a method of fabricating a magnetic field sensor includes providing
a semiconductor substrate having a planar surface. The method also
includes forming, on the planar surface, a plurality of primary
vertical Hall elements. Each one of the plurality of primary
vertical Hall elements comprises a respective plurality of vertical
Hall element contacts arranged in a respective line of primary
vertical Hall element contacts. The lines of primary vertical Hall
element contacts are arranged in a pattern representative of at
least a portion a polygonal shape. The plurality of primary
vertical Hall elements includes a primary vertical Hall element
having a respective line of vertical Hall element contacts not
parallel to a line of vertical Hall element contacts of another one
of the plurality of primary vertical Hall elements. Each one of the
plurality of primary vertical Hall elements is configured to
generate a respective magnetic field signal indicative of a
projected component of a magnetic field projected upon the plane of
the planar surface relative to an angular position of the
respective vertical Hall element. The method also includes forming,
on the semiconductor substrate, an electronic circuit coupled to
each one of the plurality of primary vertical Hall elements. The
electronic circuit is configured to generate an output signal
representative of an angle of the projected component of the
magnetic field.
[0016] In some embodiments, the method also includes forming, on
the planar surface, a plurality of secondary vertical Hall
elements. Each one of the secondary vertical Hall elements includes
a respective plurality of secondary vertical Hall element contacts
arranged in a respective line. Each one of the plurality of
secondary vertical Hall elements is arranged in a respective group
with a respective one of the plurality of primary vertical Hall
elements. Each line of secondary vertical Hall element contacts is
geometrically arranged at a predetermined angle with a respective
line of primary vertical Hall element contacts to form a plurality
of parallel groups of vertical Hall elements.
[0017] In accordance with another aspect of the present invention,
a magnetic field sensor includes a semiconductor substrate having a
planar surface. The magnetic field sensor also includes a plurality
of magnetic field sensing elements disposed on the planar surface.
The plurality of magnetic field sensing elements has a respective
plurality of major response axes, each major response axis parallel
to the major surface. The plurality of major response axes is
arranged in a pattern representative of at least a portion of a
polygonal shape. The plurality of magnetic field sensing elements
includes a primary vertical Hall element having a major response
axis not parallel to major response axis of another one of the
plurality of magnetic field sensing elements. Each one of the
plurality of magnetic field sensing elements is configured to
generate a respective magnetic field signal indicative of a
projected component of a magnetic field projected upon the plane of
the planar surface relative to an angular position of the response
axis of the respective magnetic field sensing element. The magnetic
field sensor also includes an electronic circuit disposed on the
planar surface and coupled to each one of the plurality of magnetic
field sensing elements. The electronic circuit is configured to
generate an output signal indicative of an angle of the projected
component of the magnetic field.
[0018] In some embodiments of the magnetic field sensor, the
plurality of magnetic field sensing elements comprises a plurality
of magnetoresistance elements.
[0019] In accordance with another aspect of the present invention,
a method of fabricating a magnetic field sensor includes providing
a semiconductor substrate having a planar surface. The method also
includes forming, on the planar surface, a plurality of magnetic
field sensing elements having a respective plurality of major
response axes, each major response axis parallel to the major
surface. The plurality of major response axes is arranged in a
pattern representative of at least a portion of a polygonal shape.
The plurality of magnetic field sensing elements includes a primary
vertical Hall element having a major response axis not parallel to
major response axis of another one of the plurality of magnetic
field sensing elements. Each one of the plurality of magnetic field
sensing elements is configured to generate a respective magnetic
field signal indicative of a projected component of a magnetic
field projected upon the plane of the planar surface relative to an
angular position of the response axis of the respective magnetic
field sensing element. The method also includes forming, on the
semiconductor substrate, an electronic circuit coupled to each one
of the plurality of magnetic field sensing elements. The electronic
circuit is configured to generate an output signal indicative of an
angle of the projected component of the magnetic field.
[0020] In some embodiments of the method, the plurality of magnetic
field sensing elements comprises a plurality of magnetoresistance
elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The foregoing features of the invention, as well as the
invention itself may be more fully understood from the following
detailed description of the drawings, in which:
[0022] FIG. 1 is a pictorial showing a circular vertical Hall (CVH)
sensing element having a plurality of vertical Hall elements
arranged in a circle over a common implant region in a substrate
and a two pole ring magnet disposed close to the CVH sensing
element;
[0023] FIG. 2 is a graph showing an output signal as may be
generated by the CVH sensing element of FIG. 1;
[0024] FIG. 3 is a block diagram showing an electronic circuit
using a CVH sensing element to determine a direction of a sensed
magnetic field;
[0025] FIG. 4 is a pictorial of an exemplary magnetic field sensor
having six vertical Hall elements arranged in a hexagonal pattern
over a common implant region in a substrate;
[0026] FIG. 5 is a pictorial of another exemplary magnetic field
sensor having six vertical Hall elements arranged in a hexagonal
pattern, each arranged over separate implant regions;
[0027] FIG. 6 is a pictorial of another exemplary magnetic field
sensor having six primary vertical Hall elements arranged in a
hexagonal pattern and also having six secondary vertical Hall
elements arranged in a hexagonal pattern;
[0028] FIG. 7 is a pictorial of another exemplary magnetic field
sensor having three primary vertical Hall elements arranged a
portion of (here half of) a hexagonal pattern and also having three
secondary vertical Hall elements arranged in a half of a hexagonal
pattern;
[0029] FIG. 7A is a pictorial of another exemplary magnetic field
sensor having three primary vertical Hall elements arranged in a
portion of (here half of) of a hexagonal pattern and also having
three secondary vertical Hall elements arranged in a half of a
hexagonal pattern;
[0030] FIG. 8 is a pictorial of another exemplary magnetic field
sensor having three vertical Hall elements arranged a portion of
(here half of) of a hexagonal pattern;
[0031] FIG. 8A is a pictorial of another exemplary magnetic field
sensor having three vertical Hall elements arranged a portion of
(here half of) of a hexagonal pattern; and
[0032] FIG. 9 is a graph showing output signal that can be
generated by the vertical Hall elements of the arrangement of FIGS.
4 and 5.
DETAILED DESCRIPTION OF THE INVENTION
[0033] Before describing the present invention, some introductory
concepts and terminology are explained. As used herein, the term
"magnetic field sensing element" is used to describe a variety of
electronic elements that can sense a magnetic field. The magnetic
field sensing elements can be, but are not limited to, Hall Effect
elements, magnetoresistance elements, or magnetotransistors. As is
known, there are different types of Hall Effect elements, for
example, a planar Hall element, a vertical Hall element, and a
circular Hall element. As is also known, there are different types
of magnetoresistance elements, for example, a giant
magnetoresistance (GMR) element, an anisotropic magnetoresistance
element (AMR), a tunneling magnetoresistance (TMR) element, an
Indium antimonide (InSb) sensor, and a magnetic tunnel junction
(MTJ).
[0034] As used herein, the term "sensor" is used to describe a
circuit or assembly that includes a sensing element and other
components. In particular, as used herein, the term "magnetic field
sensor" is used to describe a circuit or assembly that includes a
magnetic field sensing element and electronics coupled to the
magnetic field sensing element.
[0035] A used herein the terms "primary" and "secondary" are used
to denote different physical entities and not to denote any
structural or functional differences.
[0036] As is known, some of the above-described magnetic field
sensing elements tend to have an axis of maximum sensitivity
parallel to a substrate that supports the magnetic field sensing
element, and others of the above-described magnetic field sensing
elements tend to have an axis of maximum sensitivity perpendicular
to a substrate that supports the magnetic field sensing element. In
particular, planar Hall elements tend to have axes of sensitivity
perpendicular to a substrate, while magnetoresistance elements and
vertical Hall elements (including circular vertical Hall (CVH)
sensing elements) tend to have axes of sensitivity parallel to a
substrate.
[0037] Magnetic field sensors are used in a variety of
applications, including, but not limited to, an angle sensor that
senses an angle of a direction of a magnetic field, a current
sensor that senses a magnetic field generated by a current carried
by a current-carrying conductor, a magnetic switch that senses the
proximity of a ferromagnetic object, a rotation detector that
senses passing ferromagnetic articles, for example, magnetic
domains of a ring magnet, and a magnetic field sensor that senses a
magnetic field density of a magnetic field.
[0038] While embodiments shown and described below indicate
vertical Hall elements with vertical Hall element contacts arranged
in straight lines, in other embodiments, the vertical Hall element
contacts of one or more of the vertical Hall elements can be
arranged in respective arcs. Thus, as used herein, the term "line"
is used to describe either a straight line or a curved line.
[0039] Referring to FIG. 1, a circular vertical Hall (CVH) sensing
element 12 includes a circular implant region 18 having a plurality
of vertical Hall elements disposed thereon, of which a vertical
Hall element 12a is but one example. Each vertical Hall element has
a plurality of Hall element contacts (e.g., four or five contacts),
of which a vertical Hall element contact 12aa is but one
example.
[0040] A particular vertical Hall element (e.g., 12a) within the
CVH sensing element 12, which, for example, can have five adjacent
contacts, can share some, for example, four, of the five contacts
with a next vertical Hall element (e.g., 12b). Thus, a next
vertical Hall element can be shifted by one contact from a prior
vertical Hall element. For such shifts by one contact, it will be
understood that the number of vertical Hall elements is equal to
the number of vertical Hall element contacts, e.g., 32. However, it
will also be understood that a next vertical Hall element can be
shifted by more than one contact from the prior vertical Hall
element, in which case, there are fewer vertical Hall elements than
there are vertical Hall element contacts in the CVH sensing
element.
[0041] A center of a vertical Hall element 0 is positioned along an
x-axis 20 and a center of vertical Hall element 8 is positioned
along a y-axis 22. In the exemplary CVH 12, there are thirty-two
vertical Hall elements and thirty-two vertical Hall element
contacts. However, a CVH can have more than or fewer than
thirty-two vertical Hall elements and more than or fewer than
thirty-two vertical Hall element contacts.
[0042] In some applications, a circular magnet 14 having a south
side 14a and a north side 14b can be disposed over the CVH 12. The
circular magnet 14 tends to generate a magnetic field 16 having a
direction from the north side 14a to the south side 14b, here shown
to be pointed to a direction of about forty-five degrees relative
to x-axis 20. Other magnets having other shapes and configurations
are possible.
[0043] In some applications, the circular magnet 14 is mechanically
coupled to a rotating object (a target object), for example, an
automobile crank shaft or an automobile camshaft, and is subject to
rotation relative to the CVH sensing element 12. With this
arrangement, the CVH sensing element 12 in combination with an
electronic circuit described below can generate a signal related to
the angle of rotation of the magnet 14.
[0044] The CVH sensing element 12 can be disposed upon a substrate
26, for example, a silicon substrate, along with other electronics
(not shown).
[0045] Referring now to FIG. 2, a graph 50 has a horizontal axis
with a scale in units of CVH vertical Hall element position, n,
around a CVH sensing element, for example, the CVH sensing element
12 of FIG. 1. The graph 50 also has a vertical axis with a scale in
amplitude in units of millivolts.
[0046] The graph 50 includes a signal 52 representative of output
signal levels from the plurality of vertical Hall elements of the
CVH taken sequentially with the magnetic field of FIG. 1 stationary
and pointing in a direction of forty-five degrees.
[0047] Referring briefly to FIG. 1, as described above, vertical
Hall element 0 is centered along the x-axis 20 and vertical Hall
element 8 is centered along the y-axis 22. In the exemplary CVH
sensing element 12, there are thirty-two vertical Hall element
contacts and a corresponding thirty-two vertical Hall elements,
each vertical Hall element having a plurality of vertical Hall
element contacts, for example, five contacts.
[0048] In FIG. 2, a maximum positive signal is achieved from a
vertical Hall element centered at position 4, which is aligned with
the magnetic field 16 of FIG. 1, such that a line drawn between the
vertical Hall element contacts (e.g., five contacts) of the
vertical Hall element at position 4 is perpendicular to the
magnetic field. A maximum negative signal is achieved from a
vertical Hall element centered at position 20, which is also
aligned with the magnetic field 16 of FIG. 1, such that a line
drawn between the vertical Hall element contacts (e.g., five
contacts) of the vertical Hall element at position 20 is also
perpendicular to the magnetic field.
[0049] A sine wave 54 is provided to more clearly show the ideal
behavior of the signal 52. The signal 52 has variations due to
vertical Hall element offsets, which tend to somewhat randomly
cause element output signals to be too high or too low relative to
the sine wave 54, in accordance with offset errors for each
element. The offset signal errors are undesirable. In some
embodiments, the offset errors can be reduced by "chopping" each
vertical Hall element. Chopping will be understood to be a process
by which vertical Hall element contacts of each vertical Hall
element are driven in different configurations and signals are
received from different ones of the vertical Hall element contacts
of each vertical Hall element to generate a plurality of output
signals from each vertical Hall element. The plurality of signals
can be arithmetically processed (e.g., summed or otherwise
averaged) resulting in a signal with less offset.
[0050] Full operation of the CVH sensing element 12 of FIG. 1 and
generation of the signal 52 of FIG. 2 are described in more detail
in the above-described PCT Patent Application No.
PCT/EP2008/056517, entitled "Magnetic Field Sensor for Measuring
Direction of a Magnetic Field in a Plane," filed May 28, 2008,
which is published in the English language as PCT Publication No.
WO 2008/145662.
[0051] As will be understood from PCT Patent Application No.
PCT/EP2008/056517, groups of contacts of each vertical Hall element
can be used in a chopped arrangement to generate chopped output
signals from each vertical Hall element. Thereafter, a new group of
adjacent vertical Hall element contacts can be selected (i.e., a
new vertical Hall element), which can be offset by one or more
elements from the prior group. The new group can be used in the
chopped arrangement to generate another chopped output signal from
the next group, and so on.
[0052] Each step of the signal 52 can be representative of a
chopped output signal from one respective group of vertical Hall
element contacts, i.e., from one respective vertical Hall element.
However, in other embodiments, no chopping is performed and each
step of the signal 52 is representative of an unchopped output
signal from one respective group of vertical Hall element contacts,
i.e., from one respective vertical Hall element. Thus, the graph 52
is representative of a CVH output signal with or without the
above-described grouping and chopping of vertical Hall
elements.
[0053] It will be understood that, using techniques described above
in PCT Patent Application No. PCT/EP2008/056517, a phase of the
signal 52 (e.g., a phase of the signal 54) can be found and can be
used to identify the pointing direction of the magnetic field 16 of
FIG. 1 relative to the CVH sensing element 12.
[0054] Referring now to FIG. 3, a magnetic field sensor 70 includes
a sensing portion 71. The sensing portion 71 can include a CVH
sensing element 72 having a plurality of CVH sensing element
contacts, e.g., a CVH sensing element contact 73. In some
embodiments there are thirty-two vertical Hall elements in the CVH
sensing element 72 and a corresponding thirty-two CVH sensing
element contacts. In other embodiments there are sixty-four
vertical Hall elements in the CVH sensing element 72 and a
corresponding sixty-four CVH sensing element contacts. However, in
other embodiments, the CVH sensing element 72 can have more than or
fewer than thirty-two vertical Hall elements and/or more than or
fewer than thirty-two vertical Hall element contacts.
[0055] A magnet (not shown) can be disposed proximate to the CVH
sensing element 72, and can be coupled to a target object (not
shown). The magnet can be the same as or similar to the magnet 14
of FIG. 1
[0056] As described above, the CVH sensing element 72 can have a
plurality of vertical Hall elements, each vertical Hall element
comprising a group of vertical Hall element contacts (e.g., five
vertical Hall element contacts), of which the vertical Hall element
contact 73 is but one example.
[0057] In some embodiments, a switching circuit 74 can provide
sequential CVH differential output signals 72a, 72b from the CVH
sensing element 72.
[0058] The CVH differential output signal 72a, 72b is comprised of
sequential output signals taken one-at-a-time around the CVH
sensing element 72, wherein each output signal is generated on a
separate signal path and switched by the switching circuit 74 into
the path of the differential output signal 72a, 72b. The signal 52
of FIG. 2 can be representative of the differential signal 72a,
72b. Therefore, the CVH differential output signal 72a, 72b can be
represented as a switched set of CVH output signals x.sub.n=x.sub.0
to x.sub.N-1, taken one at a time, where n is equal to a vertical
Hall element position (i.e., a position of a group of vertical Hall
element contacts that form a vertical Hall element) in the CVH
sensing element 72, and where there are N such positions.
[0059] In one particular embodiment, the number of vertical Hall
elements (each comprising a group of vertical Hall element
contacts) in the CVH sensing element 72 is equal to the total
number of sensing element positions, N. In other words, the CVH
differential output signal 72a, 72b can be comprised of sequential
output signals, wherein the CVH differential output signal 72a, 72b
is associated with respective ones of the vertical Hall elements in
the CVH sensing element 72 as the switching circuit 74 steps around
the vertical Hall elements of the CVH sensing element 72 by
increments of one, and N equals the number of vertical Hall
elements in the CVH sensing element 72. However, in other
embodiments, the increments can be by greater than one vertical
Hall element, in which case N is less than the number of vertical
Hall elements in the CVH sensing element 72.
[0060] In one particular embodiment, the CVH sensing element 72 has
thirty-two vertical Hall elements, i.e., N=32, and each step is a
step of one vertical Hall element contact position (i.e., one
vertical Hall element position). However, in other embodiments,
there can be more than thirty-two or fewer than thirty-two vertical
Hall elements in the CVH sensing element 72, for example sixty-four
vertical Hall elements. Also, the increments of vertical Hall
element positions, n, can be greater than one vertical Hall element
contact.
[0061] In some embodiments, another switching circuit 76 can
provide the above-described "chopping" of groups of the vertical
Hall elements within the CVH sensing element 72. Chopping will be
understood to be an arrangement in which a group of vertical Hall
element contacts, for example, five vertical Hall element contacts
that form one vertical Hall element, are driven with current
sources 86 in a plurality of different connection configurations,
and signals are received from the group of vertical Hall element
contacts in corresponding different configurations to generate the
CVH differential output signal 72a, 72b. Thus, in accordance to
with each vertical Hall element position, n, there can be a
plurality of sequential output signals during the chopping, and
then the group increments to a new group, for example, by an
increment of one vertical Hall element contact.
[0062] The sensing portion 71 can also include current sources 86
configured to drive the CVH sensing element 72. While current
sources 86 are shown, in other embodiments, the current sources 86
can be replaced by voltage sources.
[0063] The magnetic field sensor 70 includes an oscillator 78 that
provides clock signals 78a, 78b, 78c, which can have the same or
different frequencies. A divider 80 is coupled to receive the clock
signal 78a and configured to generate a divided clock signal 80a. A
switch control circuit 82 is coupled to receive the divided clock
signal 80a and configured to generate switch control signals 82a,
which are received by the switching circuits 74, 76 to control the
sequencing around the CVH sensing element 72, and optionally, to
control the chopping of groups of vertical Hall elements within the
CVH sensing element 72 in ways described above.
[0064] The magnetic field sensor 70 can include a divider 88
coupled to receive the clock signal 78c and configured to generate
a divided clock signal 88a, also referred to herein as an "angle
update clock" signal.
[0065] The magnetic field sensor 70 also includes an x-y direction
component circuit 90. The x-y direction component circuit 90 can
include an amplifier 92 coupled to receive the CVH differential
output signals 72a, 72b. The amplifier 92 is configured to generate
an amplified signal 92a. A bandpass filter 94 is coupled to receive
the amplified signal 92a and configured to generate a filtered
signal 94a. A comparator 96, with or without hysteresis, is
configured to receive the filtered signal 94a. The comparator 96 is
also coupled to receive a threshold signal 120. The comparator 96
is configured to generate a thresholded signal 96a generated by
comparison of the filtered signal 94a with the threshold signal
120.
[0066] The x-y direction component circuit 90 also includes an
amplifier 114 coupled to receive the divided clock signal 88a. The
amplifier 114 is configured to generate an amplified signal 114 a.
A bandpass filter 116 is coupled to receive the amplified signal
114a and configured to generate a filtered signal 116a. A
comparator 118, with or without hysteresis, is coupled to receive
the filtered signal 116a. The comparator 118 is also coupled to
receive a threshold signal 122. The comparator 118 is configured to
generate a thresholded signal 118a by comparison of the filtered
signal 116a with the threshold signal 122.
[0067] The bandpass filters 94, 116 can have center frequencies
equal to 1/T, where T is the time that it takes to sample all of
the vertical Hall elements within the CVH sensing element 72.
[0068] It should be understood that the amplifier 114, the bandpass
filter 116, and the comparator 118 provide a delay of the divided
clock signal 88a in order to match a delay of the circuit channel
comprised of the amplifier 92, the bandpass filter 94, and the
comparator 96. The matched delays provide phase matching, in
particular, during temperature excursions of the magnetic field
sensor 70.
[0069] A counter 98 can be coupled to receive the thresholded
signal 96a at an enable input, to receive the clock signal 78b at a
clock input, and to receive the thresholded signal 118a at a reset
input.
[0070] The counter 98 is configured to generate a phase signal 98a
having a count representative of a phase difference between the
thresholded signal 96a and the thresholded signal 118a.
[0071] The phase shift signal 98a is received by a latch 100 that
is latched upon an edge of the divided clock signal 88a. The latch
100 is configured to generate a latched signal 100a, also referred
to herein as an "x-y angle signal."
[0072] It will be apparent that the latched signal 100a is a
multi-bit digital signal that has a value representative of a
direction of an angle of the magnetic field experience by the CVH
sensing element 72, and thus, an angle of the magnet and target
object. The signal 52 of FIG. 2 is representative of the latched
signal 100a.
[0073] In some embodiments, the magnetic field sensor 70 can also
include a filter 102 coupled to receive the latched signal 100a and
configured to generate a filtered signal 102a. The signal 54 of
FIG. 2 is representative of the filtered signal 102a.
[0074] In some embodiments, the clock signals 78a, 78b, 78c each
have a frequency of about 30 MHz, the divided clock signal 80a has
a frequency of about 8 MHz, and the angle update clock signal 88a
has a frequency of about 30 kHz. However in other embodiments, the
initial frequencies can be higher or lower than these
frequencies
[0075] With the magnetic field sensor 70, it will be appreciated
that an update rate of the x-y angle signal 100a occurs at a rate
equivalent to a rate at which all of the vertical Hall elements
within the CVH sensing element 72 are collectively sampled. An
exemplary rate is described below in conjunction with FIG. 4
[0076] Referring again briefly to FIG. 2, it will be understood
that all of the vertical Hall elements within the CVH sensing
element 72 are sampled in sequence to achieve an update of the x-y
angle signal 100a. Sampling all of the vertical Hall elements can
take an appreciable amount of time.
[0077] Referring now to FIG. 4, a magnetic field sensor 100
includes a semiconductor substrate 101 having a planar surface
101a. The magnetic field sensor 100 also includes a plurality of
vertical Hall elements 103, individually 102a, 102b, 102c, 102d,
102e, 102f, disposed on the planar surface 101a. Taking the
vertical Hall elements 102a as being representative of other ones
of the plurality of vertical Hall elements, each one of the
vertical Hall elements includes a respective plurality of vertical
Hall element contacts like vertical Hall element contacts 106a,
106b, 106c, 106d, 106e. Each plurality of vertical Hall element
contacts is arranged in a respective line. The lines of vertical
Hall element contacts are arranged in a pattern representative of a
polygonal shape, here a hexagon.
[0078] Each one of the plurality of vertical Hall elements 102a,
102b, 102c, 102d, 102e, 102f is configured to generate a respective
magnetic field signal responsive to of an angle of a projected
component 109 of a magnetic field projected upon the plane of the
planar surface 101a relative to an angular position of the
respective vertical Hall element. A magnet is not shown, but can be
the same as or signal to the magnet 18 of FIG. 1 and disposed
proximate to the plurality of magnetic field sensing elements 103.
Here, sequential output signals from the plurality of vertical Hall
elements 103 are indicated as a signal 103a. The signal 103a can be
similar to the differential signal 72a, 72b of FIG. 3.
[0079] Again taking the vertical Hall element 102a is being
representative of other ones of the vertical Hall elements, the
vertical Hall element 102a is operated by driving a current into
selected ones, e.g., two, of the vertical Hall element contacts
106a, 106b, 106d, 106d, 106e, in which case, an output signal is
generated at the non-selected ones, e.g., three, of the vertical
Hall element contacts. In a chopping process, used to reduce the
effect of any offset voltage of the vertical Hall element 102a, the
selection of vertical Hall element contacts that are driven and
vertical Hall element contacts from which output signals are
received can be changed in a chopping sequence in a plurality of
so-called "phases." Typical chopping arrangements use two such
phases, referred to herein as 2.times., or four such phases,
referred to herein as 4.times., however, other chopping
arrangements are also possible.
[0080] The magnetic field sensor 100 can also include an electronic
circuit 108 disposed on the planar surface 101a and coupled to each
one of the plurality of vertical Hall elements 103. The electronic
circuit 108 is configured to generate an output signal 108a
indicative of the angle of the projected component of the magnetic
field. The electronic circuit 108 can be the same as or similar to
that shown above in conjunction with FIG. 3, wherein the CVH
sensing element 72 is replaced by the plurality of vertical Hall
elements 103.
[0081] In operation, each one of the plurality of vertical Hall
elements 103 can be processed by the electronic circuit 108
sequentially. Unlike the magnetic field sensor 70 of FIG. 3, for
which vertical Hall elements within the CVH sensing element 72
overlap and share vertical Hall element contacts, here, the
plurality of vertical Hall elements 103 does not share vertical
Hall element contacts. It will become apparent from discussion
below in conjunction with FIG. 9 that such an arrangement tends to
generate an output signal that has fewer and larger steps than the
output signal 52 of FIG. 2. However, the filter 102 of FIG. 3 can
be adjusted to smooth out the steps. Because there are fewer steps
in the output signal (see, e.g., FIGS. 2 and 9), a magnetic field
sensor, like the magnetic field sensor 70 of FIG. 3, that uses the
plurality of vertical Hall elements 103, can run at high speeds
(i.e., speeds of rotation of a sensed magnetic field). The filter
102 introduces a fixed time delay, but does not necessarily impact
the speed of operation, i.e., throughput of output samples.
[0082] The plurality of vertical Hall elements 103 includes, and is
arranged over, a common implant region in the planar surface 101a
of the substrate 101.
[0083] Referring briefly again to FIG. 3, in some embodiments, the
electronic circuit 108 can include first and second vertical Hall
element driving circuits 86a, 86b, respectively. The switching
circuit 74 can be coupled between the first and second vertical
Hall element driving circuits 86a, 86b and the plurality of
vertical Hall elements 103. Not to be confused with chopping, which
dwells upon one vertical Hall element at a time, the switching
circuit 74 can be configured to switch couplings between the first
and second vertical Hall element driving circuits 86a, 86b and the
plurality of vertical Hall elements 103, e.g., a changing two of
the plurality of vertical Hall elements 103 . . . . During a time
when one of the plurality of vertical Hall elements 103 is being
driven by the first vertical Hall element driving circuit 86a and
processed by the electronic circuit 108, another one of the
plurality of vertical Hall elements 103 can be driven by the second
vertical Hall element driving circuit 86b. With this arrangement,
the electronic circuit 108 can more rapidly sequence through the
plurality of vertical Hall elements, since a next vertical Hall
element can be ready for sampling when sampling of a present
vertical Hall element is complete.
[0084] As described above, each one of the plurality of vertical
Hall elements 102a, 102b, 102c, 102d, 102e, 102f is responsive to
(i.e., differently responsive to) the magnetic field 109 (or the
projection 109 of a magnetic field) in the plane of the surface
101a of the substrate 101. In particular, each vertical Hall
element generates (sequentially) an output signal related to an
angle of the magnetic field 109 relative to an orientation of the
respective vertical Hall element. For the magnetic field 109 shown
at a particular angle, the vertical Hall elements 102b, 102e, for
which lines between associated vertical Hall element contacts are
perpendicular to the magnetic field 109, have the greatest
sensitivity. One of the vertical Hall elements 102b, 102e generates
a largest positive output signal and the other one of the vertical
Hall elements 102b, 102e generates a largest negative output
signal. Other ones of the vertical Hall elements generate smaller
output signals.
[0085] For the magnetic field 109 shown at the particular angle, it
will also be appreciated that the vertical Hall elements 102b, 102e
generate output signals with approximately the same amplitude but
with opposite signs. The amplitudes of the output signals from the
two vertical Hall elements 102b, 102e, i.e., a pair of vertical
Hall elements, differ by small amounts due to small differences in
sensitivity of the two vertical Hall elements 102b, 102e, due to
small differences in offset voltage of the two vertical Hall
elements 102b, 102e, and also due to position placement inaccuracy
of the plurality of magnetic field sensing elements 103 relative to
a magnet (not shown). The sensitivity difference can be reduced by
integrated circuit fabrication techniques, including dimensional
and process control. The offset voltage differences can be reduced
by various techniques, for example, the above-described
chopping.
[0086] For the magnetic field 109 shown at the particular angle,
other pairs of vertical Hall elements also generate output signals
with the same amplitude but with different signs. The vertical Hall
element pair 102c, 102f and also the vertical Hall element pair
102a, 102d generate output signals with the same amplitude but with
different signs, each pair producing output signals with smaller
amplitudes than the vertical Hall element pair 102b, 102e.
[0087] For a magnetic field at other angles in the plane of the
surface 101a, similarly, pairs of vertical Hall elements generate
output signals with substantially the same amplitudes, but with
opposite signs. Thus, as described below in conjunction with FIGS.
7, 7A, 8, and 8A, it is possible to remove some of the vertical
Hall elements, for example, one, two, or three of the vertical Hall
elements 102a, 102b, 102d, 102d, 102e, 102f and to still
reconstruct the output signal using only the remaining vertical
Hall elements.
[0088] The magnetic field sensor 100 can generate an output signal
more rapidly indicative of an angle of a magnetic field that the
CVH sensing element of FIGS. 1 and 3. The CVH sensing element
described above in conjunction with FIG. 1 and the magnetic field
sensor described above in conjunction with FIG. 3, when used with a
4.times. (four phase) chopping, with a CVH sensing element with 64
CVH sensing elements, and with a master clock frequency of 8 MHz
(see, e.g., clock 80a of FIG. 3), results in a CVH sensing element
sequence frequency (frequency of sample revolutions around CVH
sensing element) of 31.25 kHz. This frequency is equivalent to a
response time of the CVH sensing element (like cycle time of FIG.
2, but for 64 CVH sensing elements) of about thirty-two
microseconds.
[0089] In comparison, the magnetic field sensor 100 of FIG. 4, when
used with 4.times. chopping, with six vertical Hall elements as
shown, and with a master clock of 8 MHz, results in a sequence
frequency of 333 kHz and a response time of about three
microseconds, much faster than the CVH sensing element.
Furthermore, techniques described below in conjunction with FIGS.
7, 7A, 8, and 8A can reduce the number of vertical Hall elements
further, for example, to three vertical Hall elements, resulting in
a response time of about 1.5 microseconds. As described below,
while hexagonal patterns of vertical Hall elements are used in
examples herein, other patterns are also possible.
[0090] Referring now to FIG. 5, a magnetic field sensor 110 is like
the magnetic field sensor 100 of FIG. 4. However the magnetic field
sensor 110 includes a plurality of vertical Hall elements 113,
individually 112a, 112b, 112c, 112d, 112e, 112f, arranged over
separate implant regions 114a, 114b, 114c, 114d, 114d, 114f,
respectively, in a substrate 111.
[0091] The magnetic field sensor 110 can be arranged on the
semiconductor substrate 111 having a planar surface 111a.
[0092] An electronic circuit 118 is coupled to receive signals 113a
from the plurality of vertical Hall elements 113. The electronic
circuit 118 is configured to generate an output signal 118a. The
electronic circuit 118 and the output signal 118a can be the same
as or similar to the electronic circuit 108 and the output signal
108a of FIG. 4.
[0093] Referring now to FIG. 6, a magnetic field sensor 120
includes a semiconductor substrate 121 having a planar surface
121a. The magnetic field sensor 120 also includes a plurality of
vertical Hall elements 123. The plurality of vertical Hall elements
123 includes, as a primary plurality of vertical Hall elements, the
vertical Hall elements 112a, 112b, 112c, 112d, 112e, 112f of FIG.
5. Unlike the magnetic field sensor 110 of FIG. 5, the plurality of
vertical Hall elements 123 also includes, as a secondary plurality
of vertical Hall elements, vertical Hall elements 122a, 122b, 122c,
122d, 122e, 122f. The secondary plurality of vertical Hall elements
is arranged over separate implant regions 124a, 124b, 124c, 124d,
124e, 124f respectively. However, like the arrangement of FIG. 4,
in other embodiments, the primary plurality of vertical Hall
elements 112a, 112b, 112c, 112d, 112e, 112f can be arranged over a
first common implant region and the secondary plurality of vertical
Hall elements 122a, 122b, 122c, 122d, 122e, 122f can be arranged
over a second common implant region in the substrate 121.
[0094] Taking the secondary vertical Hall element 122a as being
representative of other ones of the plurality of vertical Hall
elements, each one of the secondary plurality of vertical Hall
elements includes a respective plurality of vertical Hall element
contacts like vertical Hall element contacts 116a, 116b, 116c,
116d, 116e. Each plurality of secondary vertical Hall element
contacts is arranged in a respective line. The lines of secondary
vertical Hall element contacts are arranged in a pattern
representative of a polygonal shape, here a hexagon. Each one of
the lines of the secondary vertical Hall element contacts can be
geometrically parallel to a respective line of the primary vertical
Hall element contacts. However, in other embodiments, the polygon
of secondary vertical Hall elements can be rotated in relation to
the polygon of primary vertical Hall elements. The rotation can be
small, for example, 0.1 degrees, or the rotation can be large, for
example thirty degrees.
[0095] Each one of the primary plurality of vertical Hall elements
112a, 112b, 112c, 112d, 112e, 112f and each one of the secondary
plurality of vertical Hall elements 122a, 122b, 122c, 122d, 122e,
122f is configured to generate a respective magnetic field signal
responsive to of an angle of a projected component of a magnetic
field (see, e.g., 110 of FIG. 4) projected upon the plane of the
planar surface 121a relative to an angular position of the
respective vertical Hall element. Here, sequential output signals
from plurality of vertical Hall elements 123 are indicated as a
signal 123a. The signal 123a can be similar to the differential
signal 72a, 72b of FIG. 3 and similar to the signal 103a of FIG. 4
and the signal 113a of FIG. 5.
[0096] The magnetic field sensor 120 can also include an electronic
circuit 126 disposed on the planar surface 121a and coupled to each
one of the plurality of vertical Hall elements 123. The electronic
circuit 126 is configured to generate an output signal 126a
indicative of the angle of the projected component of the magnetic
field. The electronic circuit can be the same as or similar to that
shown above in conjunction with FIG. 3, wherein the CVH sensing
element 72 is replaced by the plurality of vertical Hall elements
123.
[0097] In operation, in some embodiments, each one of the plurality
of vertical Hall elements 123 can be processed by the electronic
circuit 126 sequentially, resulting in a pattern of twelve
sequential samples within the signal 123a. Unlike the magnetic
field sensor 70 of FIG. 3, for which vertical Hall elements within
the CVH sensing element 72 overlap and share vertical Hall element
contacts, here, the vertical Hall elements 123 do not share
vertical Hall element contacts. It will become apparent from
discussion below in conjunction with FIG. 9 that such an
arrangement tends to generate an output signal that has fewer and
larger steps than the output signal 52 of FIG. 2. However, the
filter 102 of FIG. 3 can be adjusted to smooth out the steps.
[0098] In some embodiments, each one of the primary plurality of
vertical Hall elements 112a, 112b, 112c, 112d, 112e, 112f is
electronically coupled in parallel with an adjacent one of the
secondary plurality of vertical Hall elements 122a, 122b, 122c,
122d, 122e, 122f, resulting in a pattern of six sequential samples
within the signal 123a.
[0099] The electronically parallel arrangement can be accomplished
in two different ways. In a first parallel coupling, only output
signals of each adjacent pair of the plurality of vertical Hall
elements 123 are coupled in parallel. In the first parallel
coupling, drive signals provided to each one of the plurality of
vertical Hall elements 123 in an adjacent pair of vertical Hall
elements can be different. In particular, for embodiments that use
chopping, the different drive signals can be at different chopping
phases at any time.
[0100] In a second parallel coupling, output signals of each
adjacent pair of the plurality of vertical Hall elements 123 are
coupled in parallel, and also the drive signals to each adjacent
pair of the plurality of vertical Hall elements 123 are coupled in
parallel.
[0101] In yet another parallel arrangement, output signals from
each adjacent pair of the plurality of vertical Hall elements 123
are summed at a subsequent amplifier, with or without parallel
drive signals to the vertical Hall elements 123.
[0102] It should be appreciated that, with either electronically
parallel coupled arrangement of the vertical Hall elements, output
signal with higher signal to noise ratios are generated by each
parallel pair of vertical Hall elements, higher than that which
would be generated by any one vertical Hall element. Thus, the
magnetic field sensor 120 can achieve higher signal-to-noise ratios
than the magnetic field sensors 100, 110 of FIG. 4 or 5.
[0103] While the plurality of vertical Hall elements 123 is shown
to include parallel pairs of vertical Hall elements, in other
embodiments, there can be parallel groups of vertical Hall
elements, each parallel group having two or more geometrically
parallel vertical Hall elements.
[0104] Referring now to FIG. 7, a magnetic field sensor 130
includes a semiconductor substrate 131 having a planar surface
131a. The magnetic field sensor 130 also includes a plurality of
vertical Hall elements 133. The plurality of vertical Hall elements
133 includes, as a primary plurality of vertical Hall elements,
primary vertical Hall elements 132a, 132b, 132c. The plurality of
vertical Hall elements 133 also includes, as a secondary plurality
of vertical Hall elements, secondary vertical Hall elements 136a,
136b, 136c. The primary and secondary pluralities of vertical Hall
elements are arranged over separate implant regions 134a, 134b,
134c, 138a, 138b, 138c.
[0105] Each one of the primary vertical Hall elements and each one
of the secondary vertical Hall elements includes a respective
plurality of vertical Hall element contacts. Each plurality of
primary vertical Hall elements contacts and each plurality of
secondary vertical Hall element contacts is arranged in a
respective line. The lines of primary and secondary vertical Hall
element contacts are arranged in a pattern representative of a
portion of polygonal shape, here a portion of a hexagon. Each one
of the lines of the secondary vertical Hall element contacts can be
geometrically parallel to a respective line of the primary vertical
Hall element contacts. However, in other embodiments, each line of
secondary vertical Hall elements can be rotated in relation to a
respective line of primary vertical Hall elements. The rotation can
be small, for example, 0.1 degrees, or the rotation can be large,
for example thirty degrees.
[0106] Each one of the primary plurality of vertical Hall elements
132a, 132b, 132c and each one of the secondary plurality of
vertical Hall elements 136a, 136b, 136c is configured to generate a
respective magnetic field signal responsive to of an angle of a
projected component of the magnetic field projected upon the plane
of the planar surface relative to an angular position of the
respective vertical Hall element. Here, sequential output signals
from plurality of vertical Hall elements 133 are indicated as a
signal 133a. The signal 133a can be similar to the differential
signal 72a, 72b of FIG. 3 and similar to the signal 103a of FIG. 4,
the signal 113a of FIG. 5, and the signal 123a of FIG. 6.
[0107] The magnetic field sensor 130 can also include an electronic
circuit 140 disposed on the planar surface 131a and coupled to each
one of the plurality of vertical Hall elements 133. The electronic
circuit 136 is configured to generate an output signal 140a. The
magnetic field sensor 130 can also include a pattern completion
generator 142 coupled to receive the output signal 140a and
configured to generate an output signal 142a indicative of the
angle of the projected component of the magnetic field. The
electronic circuit 140 can be the same as or similar to that shown
above in conjunction with FIG. 3, wherein the CVH sensing element
72 is replaced by the plurality of vertical Hall elements 133.
[0108] The electronic circuit 140 and the pattern completion
generator 142 are both electronic circuits disposed upon the
substrate 131, and both together are referred to herein as an
electronic circuit.
[0109] In operation, in some embodiments, each one of the plurality
of vertical Hall elements 133 can be processed by the electronic
circuit 140 sequentially, resulting in a pattern of six sequential
samples within the signal 133a. Unlike the magnetic field sensor 70
of FIG. 3, for which vertical Hall elements within the CVH sensing
element 72 overlap and share vertical Hall element contacts, here,
the plurality of vertical Hall elements 133 do not share vertical
Hall element contacts. It will become apparent from discussion
below in conjunction with FIG. 9 that such an arrangement tends to
generate an output signal that has fewer and larger steps than the
output signal 52 of FIG. 2. However, the filter 102 of FIG. 3 can
be adjusted to smooth out the steps.
[0110] In some embodiments, each one of the primary plurality of
vertical Hall elements 132a, 132b, 132c is electronically coupled
in parallel with an adjacent one of the secondary plurality of
vertical Hall elements 136a, 136b, 136c, resulting in a pattern of
three sequential samples within the signal 133a.
[0111] As described above in conjunction with FIG. 6, the
electronically parallel arrangement can be accomplished in
different ways. In a first parallel coupling, only output signals
of each adjacent pair of the vertical Hall elements are coupled in
parallel. In the first parallel coupling, drive signals provided to
each one of the vertical Hall elements in an adjacent pair of
vertical Hall elements can be different. In particular, for
embodiments that use chopping, the different drive signals can be
at different chopping phases at any time.
[0112] In a second parallel coupling, output signals of each
adjacent pair of the vertical Hall elements are coupled in
parallel, and also the drive signals to each adjacent pair of the
vertical Hall elements are coupled in parallel.
[0113] In other embodiment, signals from lines of the primary and
secondary vertical Hall elements can be combined at a subsequent
amplifier.
[0114] It should be appreciated that, with either electronically
parallel arrangement of the vertical Hall elements, output signals
generated by each parallel pair of vertical Hall elements are
larger than that which we would be generated by any one vertical
Hall element. Thus, the magnetic field sensor 130 can achieve
higher signal-to-noise ratios than the magnetic field sensors 100,
110 of FIG. 4 or 5.
[0115] Unlike the magnetic field sensors of FIGS. 4-6, the
plurality of vertical Hall elements 133 is representative of only a
portion of a polygonal shape. However, as described above in
conjunction with FIG. 4, the plurality of vertical Hall elements
133 can be used to deduce other output signals as may be generated
by vertical Hall elements that would otherwise form missing sides
of the polygonal shape. Referring briefly to FIG. 6, it will be
understood that vertical Hall elements on opposite sides of the
hexagonal shape have opposite output signals (i.e., signal values)
but of the same amplitude when the magnetic field sensor 120 of
FIG. 6 experiences a magnetic field in the plane of the surface
121a. Thus, if a pair of vertical Hall elements 132b, 136b of FIG.
7 is like a pair of vertical Hall elements 112c, 122c of FIG. 6,
then a signal that would otherwise be generated by a pair of
vertical Hall elements 112f, 124f of FIG. 6, counterparts of which
are not present in FIG. 7, can be deduced or calculated by
generating another signal as an opposite of the signal generated by
the pair of vertical Hall elements 132b, 136b. Therefore, even
though the plurality of vertical Hall elements 133 is
representative of only a portion of a polygonal shape, for example,
half of a hexagon, electronic magnetic field signals that would
otherwise be generated by the other half of the hexagon, which is
not present, can be calculated from the electronic magnetic field
signals generated by the vertical Hall elements that are
present.
[0116] To this end, in order to represent a complete polygon, the
pattern completion generator 142 completes the hexagonal pattern by
deducing or calculating electronic signals from those within the
output signal 140a, which calculated electronic signals are not
directly generated by the plurality of vertical Hall elements
133.
[0117] While the plurality of vertical Hall elements 133 is shown
to include parallel pairs of vertical Hall elements, in other
embodiments, there can be parallel groups of vertical Hall
elements, each parallel group having two or more geometrically
parallel vertical Hall elements.
[0118] Comparing the magnetic field sensor 130 to the magnetic
field sensor 120 of FIG. 6, because the magnetic field sensor 130
only generates the output signals 133a from three parallel pairs of
vertical Hall elements and calculates other signals to represent a
complete polygonal shape of vertical Hall elements, the magnetic
field sensor 130 can achieve an indication of the angle of the
magnetic field faster than the magnetic field sensor 120 of FIG.
6.
[0119] Referring now to FIG. 7A, a magnetic field sensor 150 is
similar to the magnetic field sensor 130 of FIG. 7. However, the
magnetic field sensor 150 includes a plurality of vertical Hall
elements 153 that are representative of a different portion of a
polygonal shape than the plurality of vertical Hall elements 133 of
FIG. 7. Nevertheless, elements of and function of the magnetic
field sensor 150 will be understood from the discussion above in
conjunction with FIG. 7.
[0120] Referring now to FIG. 8, a magnetic field sensor 170 is also
similar to the magnetic field sensor 130 of FIG. 7. However, the
magnetic field sensor 170 includes a plurality of vertical Hall
elements 173 having only three vertical Hall elements 172a, 172b,
172c. The plurality of vertical Hall elements 173 does not include
a secondary plurality of vertical Hall elements. An electronic
circuit 176 and a pattern generator 178 can be the same as or
similar to those described above in conjunction with FIG. 7.
Elements of and function of the magnetic field sensor 170 will be
understood from the discussion above in conjunction with FIG.
7.
[0121] Referring now to FIG. 8A, a magnetic field sensor 190 is
also similar to the magnetic field sensor 150 of FIG. 7A. However,
the magnetic field sensor 170 includes a plurality of vertical Hall
elements 193 having only three vertical Hall elements 192a, 192b,
192c. The plurality of vertical Hall elements 193 does not include
a secondary plurality of vertical Hall elements. An electronic
circuit 196 and a pattern generator 198 can be the same as or
similar to those described above in conjunction with FIG. 7.
Elements of and function of the magnetic field sensor 190 will be
understood from the discussion above in conjunction with FIGS. 7
and 7A.
[0122] While examples above show six (or twelve) vertical Hall
elements with lines of vertical Hall element contacts arranged in
hexagonal polygonal shapes, in other embodiments, other numbers of
vertical Hall elements can be arranged with vertical Hall element
contacts arranged in lines representative of other polygonal shapes
having any number of sides greater than three sides.
[0123] While examples above show three (or six) vertical Hall
elements with lines of vertical Hall element contacts arranged in
half of hexagonal polygonal shapes, in other embodiments, other
numbers of vertical Hall elements can be arranged with vertical
Hall element contacts arranged in lines representative of other
portions of polygonal shapes, for example, three quarters of a
polygonal shape.
[0124] While vertical Hall elements having five vertical Hall
element contacts are shown in examples above, in other embodiments,
each vertical Hall element can have more than five or fewer than
five vertical Hall element contacts.
[0125] Referring now to FIG. 9 is a graph 210 is similar to the
graph 50 of FIG. 2. The graph 50 has a horizontal axis with a scale
in units of vertical Hall element position, n, around a polygonal
arrangement of vertical Hall elements, for example, around the
plurality of vertical Hall elements 103 of FIG. 4. The graph 210
also has a vertical axis with a scale in amplitude in units of
millivolts.
[0126] The graph 210 includes a signal 212 representative of output
signal levels from the plurality of vertical Hall elements of 102a,
102b, 102c, 102d, 102e, 102f of FIG. 4 taken sequentially when in
the presence of a magnetic field, stationary and pointing in a
direction of sixty degrees.
[0127] In FIG. 9, a maximum positive signal is achieved from one of
the six vertical Hall elements 102a, 102b, 102c, 102d, 102e, 102f,
which is best aligned with the magnetic field at sixty degrees,
such that the line of vertical Hall element contacts (e.g., five
contacts) of the vertical Hall element is closest to perpendicular
to the magnetic field. A maximum negative signal is achieved from
another vertical Hall, which is also aligned with the magnetic
field 16 of FIG. 1, such that the line of vertical Hall element
contacts (e.g., five contacts) of the vertical Hall element is also
perpendicular to the magnetic field.
[0128] A sine wave 214 is provided to more clearly show the ideal
behavior of the signal 212. The sine wave can be generated by the
filter 102 of FIG. 3.
[0129] The signal 214 can have variations due to vertical Hall
element offsets, which tend to somewhat randomly cause element
output signals to be too high or too low relative to the sine wave
214, in accordance with offset errors for each element. The offset
signal errors are undesirable. In some embodiments, the offset
errors can be reduced by the use of chopping described above.
Chopping, as described above in conjunction with FIG. 4, will be
understood to be a process by which vertical Hall element contacts
of each vertical Hall element are driven in different
configurations and signals are received from different ones of the
vertical Hall element contacts of each vertical Hall element to
generate a plurality of output signals from each vertical Hall
element. The plurality of signals can be arithmetically processed
(e.g., summed or otherwise averaged) resulting in a signal with
less offset. An offset generated by the vertical Hall elements
induces non linearity in the sinusoidal signal (see, e.g., FIGS. 2
and 9) that can be further reduced with a filter (not shown)
centered at or near the sinusoidal frequency.
[0130] Groups of contacts of each vertical Hall element can be used
in a chopped arrangement to generate chopped output signals from
each vertical Hall element. Thereafter, a new group of adjacent
vertical Hall element contacts can be selected (i.e., a new
vertical Hall element). The new group can be used in the chopped
arrangement to generate another chopped output signal from the next
group, and so on.
[0131] Each step of the signal 212 can be representative of a
chopped output signal from one respective group of vertical Hall
element contacts, i.e., from one respective vertical Hall element.
However, in other embodiments, no chopping is performed and each
step of the signal 212 is representative of an unchopped output
signal from one respective group of vertical Hall element contacts,
i.e., from one respective vertical Hall element. Thus, the graph
212 is representative of a CVH output signal with or without the
above-described grouping and chopping of vertical Hall
elements.
[0132] It will be understood from discussion above in conjunction
with FIG. 3, that a phase of the signal 212 (e.g., a phase of the
signal 214) can be found and can be used to identify the pointing
direction of the magnetic field relative to the polygonal pattern
of vertical Hall elements.
[0133] While embodiments shown and described above indicate
vertical Hall elements, in other embodiments, one or more of the
vertical Hall elements can instead be a respective one or more
magnetoresistance elements having respective axes of sensitivity
aligned in the same directions as those of the above-described
vertical Hall elements. Also, other types of magnetic field sensing
elements are possible, so long as they have axis of sensitivity
aligned in the same directions as those of the above-described
vertical Hall elements. It will be apparent how to modify the
electronic circuit of FIG. 3 to use the various other types of
magnetic field sensing elements.
[0134] All references cited herein are hereby incorporated herein
by reference in their entirety.
[0135] Having described preferred embodiments, which serve to
illustrate various concepts, structures and techniques, which are
the subject of this patent, it will now become apparent to those of
ordinary skill in the art that other embodiments incorporating
these concepts, structures and techniques may be used. Accordingly,
it is submitted that that scope of the patent should not be limited
to the described embodiments but rather should be limited only by
the spirit and scope of the following claims.
* * * * *