U.S. patent application number 15/892843 was filed with the patent office on 2019-08-15 for magnetic field sensor having at least two cvh elements and method of operating same.
This patent application is currently assigned to Allegro MicroSystems, LLC. The applicant listed for this patent is Allegro MicroSystems, LLC. Invention is credited to Andrea Foletto, Andreas P. Friedrich, Nicolas Yoakim.
Application Number | 20190250222 15/892843 |
Document ID | / |
Family ID | 67541529 |
Filed Date | 2019-08-15 |
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United States Patent
Application |
20190250222 |
Kind Code |
A1 |
Friedrich; Andreas P. ; et
al. |
August 15, 2019 |
Magnetic Field Sensor Having at Least Two CVH Elements and Method
of Operating Same
Abstract
A magnetic field sensor for sensing a direction of a magnetic
field in an x-y plane, can include a first plurality of magnetic
field sensing elements operable to generate a first plurality of
magnetic field signals and a second plurality of magnetic field
sensing elements operable to generate a second plurality of
magnetic field signals. The magnetic field sensor can also include
at least one sequence switches circuit operable to select ones of
the first plurality of magnetic field signals and to select ones of
the second plurality of magnetic field signals. The magnetic field
sensor can also include a processing circuit operable to combine
the selected ones of the first plurality of magnetic field signals
and the selected ones of the second plurality of magnetic field
signals to generate at least one sequential signal and to process
the at least one sequential signal to generate an x-y angle signal
indicative of a direction of the magnetic field in the x-y
direction. An associated method is described.
Inventors: |
Friedrich; Andreas P.;
(Metz-Tessy, FR) ; Foletto; Andrea; (Annecy,
FR) ; Yoakim; Nicolas; (Morges, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Allegro MicroSystems, LLC |
Worcester |
MA |
US |
|
|
Assignee: |
Allegro MicroSystems, LLC
Worcester
MA
|
Family ID: |
67541529 |
Appl. No.: |
15/892843 |
Filed: |
February 9, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 33/0005 20130101;
G01R 33/077 20130101; G01R 33/075 20130101; G01R 33/0094 20130101;
G01R 33/091 20130101 |
International
Class: |
G01R 33/07 20060101
G01R033/07; G01R 33/00 20060101 G01R033/00 |
Claims
1. A magnetic field sensor for sensing a direction of a magnetic
field in an x-y plane, the magnetic field sensor comprising: a
first plurality of magnetic field sensing elements operable to
generate a first plurality of magnetic field signals, the first
plurality of magnetic field sensing elements having a respective
first plurality of maximum response axes aligned in a respective
first plurality of different directions in the x-y plane; a second
plurality of magnetic field sensing elements operable to generate a
second plurality of magnetic field signals different than the first
plurality of magnetic field signals, the second plurality of
magnetic field sensing elements having a respective second
plurality of maximum response axes aligned in a respective second
plurality of directions in the x-y plane, wherein the first
plurality of directions and the second plurality of directions
comprise the same plurality of directions or different pluralities
of directions; at least one sequence switches circuit operable to
select ones of the first plurality of magnetic field signals and to
select ones of the second plurality of magnetic field signals; and
a processing circuit operable to combine the selected ones of the
first plurality of magnetic field signals and the selected ones of
the second plurality of magnetic field signals to generate at least
one sequential signal and to process the at least one sequential
signal to generate an x-y angle signal indicative of a direction of
the magnetic field in the x-y plane.
2. The magnetic field sensor of claim 1, wherein the selected ones
of the first plurality of magnetic field signals comprises a first
sequential signal and the selected ones of the second plurality of
magnetic field signals comprises a second sequential signal
different than the first sequential signal, and wherein the
processing circuit comprises a summing node or differencing node
coupled to receive a first signal representative of the first
sequential signal, coupled to receive a second signal
representative of the second sequential signal, and configured to
generate a combined sequential signal as a sum or a difference of
the first signal and the second signal.
3. The magnetic field sensor of claim 1, wherein the selected ones
of the first plurality of magnetic field signals comprises a first
sequential signal and the selected ones of the second plurality of
magnetic field signals comprises a second sequential signal
different than the first sequential signal, and wherein the
processing circuit comprises a multiplication node coupled to
receive a first signal representative of the first sequential
signal, coupled to receive a second signal representative of the
second sequential signal, and configured to generate a combined
sequential signal as a product of the first signal and the second
signal.
4. The magnetic field sensor of claim 3, wherein the processing
circuit further comprises a filter coupled to the multiplication
node and operable to remove higher harmonics within the combined
sequential signal.
5. The magnetic field sensor of claim 1, wherein the first
plurality of magnetic field sensing elements is angularly aligned
in the x-y plane with the second plurality of magnetic field
sensing elements.
6. The magnetic field sensor of claim 5, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element, and wherein the angular alignment corresponds to an
alignment in the x-y plane between contacts of the first and the
second CVH elements.
7. The magnetic field sensor of claim 1, wherein the first
plurality of magnetic field sensing elements is angularly
misaligned in the x-y plane by a predetermined misalignment angle
from the second plurality of magnetic field sensing elements
8. The magnetic field sensor of claim 7, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element, and wherein the predetermined misalignment angle
corresponds to an angle in the x-y plane between a contact of the
first CVH element and a contact of the second CVH element being
half of an angle between adjacent contacts of the first CVH
element.
9. The magnetic field sensor of claim 1, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, and wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element.
10. The magnetic field sensor of claim 1, wherein the at least one
sequential signal consists of one combined sequential signal
comprising alternating selected sequential ones of the first
plurality of magnetic field signals and the second plurality of
magnetic field signals.
11. The magnetic field sensor of claim 10, wherein adjacent ones in
time of the sequentially selected ones of the first plurality of
magnetic fields signals and the sequentially selected ones of the
second plurality of magnetic field signals are derived from
magnetic field sensing elements within the first plurality of
magnetic field sensing elements and magnetic field sensing elements
within the second plurality of magnetic field sensing elements that
are angularly aligned in the x-y plane.
12. The magnetic field sensor of claim 11, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element, and wherein the angular alignment comprises an
alignment in the x-y plane between contacts of the first and the
second CVH elements.
13. The magnetic field sensor of claim 10, wherein adjacent ones in
time of the sequentially selected ones of the first plurality of
magnetic fields signals and the sequentially selected ones of the
second plurality of magnetic field signals are derived from
magnetic field sensing elements within the first plurality of
magnetic field sensing elements and magnetic field sensing elements
within the second plurality of magnetic field sensing elements that
are angularly separated in the x-y plane by a predetermined angular
separation angle.
14. The magnetic field sensor of claim 13, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element, and wherein the angular separation angle corresponds
to an angle in the x-y plane of about ninety degrees.
15. The magnetic field sensor of claim 13, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element, and wherein the angular separation angle corresponds
to an angle in the x-y plane of about one hundred eighty
degrees.
16. The magnetic field sensor of claim 13, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element, and wherein the angular separation angle corresponds
to angle in the x-y plane between a contact of the first CVH
element and a contact of the second CVH element being half of an
angle between adjacent contacts of the first CVH element.
17. The magnetic field sensor of claim 1, wherein the at least one
sequential signal comprises a first sequential signal and a second
sequential signal different than the first sequential signal, the
first sequential signal comprising sequentially selected ones of
the first plurality of magnetic field signals, and the second
sequential signal comprising sequentially selected ones of the
second plurality of magnetic field signals.
18. The magnetic field sensor of claim 17, wherein adjacent ones in
time of the sequentially selected ones of the first plurality of
magnetic fields signals and the sequentially selected ones of the
second plurality of magnetic field signals are derived from
magnetic field sensing elements within the first plurality of
magnetic field sensing elements and magnetic field sensing elements
within the second plurality of magnetic field sensing elements that
are angularly aligned in the x-y plane.
19. The magnetic field sensor of claim 18, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element, and wherein the angular alignment comprises an
alignment in the x-y plane between a contact of the first CVH
element and a contact of the second CVH element.
20. The magnetic field sensor of claim 17, wherein adjacent ones in
time of the sequentially selected ones of the first plurality of
magnetic fields signals and the sequentially selected ones of the
second plurality of magnetic field signals are derived from
magnetic field sensing elements within the first plurality of
magnetic field sensing elements and magnetic field sensing elements
within the second plurality of magnetic field sensing elements that
are angularly separated in the x-y plane by a predetermined angular
separation angle.
21. The magnetic field sensor of claim 20, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element, and wherein the angular separation angle corresponds
to an angle in the x-y plane of about ninety degrees.
22. The magnetic field sensor of claim 20, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element, and wherein the angular separation angle corresponds
to an angle in the x-y plane of about one hundred eighty
degrees.
23. The magnetic field sensor of claim 20, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element, and wherein the angular separation angle corresponds
to angle in the x-y plane between a contact of the first CVH
element and a contact of the second CVH element being half of an
angle between adjacent contacts of the first CVH element.
24. The magnetic field sensor of claim 1, wherein the first
plurality of magnetic field sensing elements comprises a first CVH
element, wherein the second plurality of magnetic field sensing
elements comprises a second CVH element different than the first
CVH element, and wherein the processing circuit is operable to
combine the selected ones of the first plurality of magnetic field
signals and the selected ones of the second plurality of magnetic
field signals in a differential arrangement.
25. A method of sensing a direction of a magnetic field in an x-y
plane, the method comprising: generating a first plurality of
magnetic field signals with a first plurality of magnetic field
sensing elements, the first plurality of magnetic field sensing
elements having a respective first plurality of maximum response
axes aligned in a respective first plurality of different
directions in the x-y plane; generating a second plurality of
magnetic field signals different than the first plurality of
magnetic field signals with a second plurality of magnetic field
sensing elements, the second plurality of magnetic field sensing
elements having a respective second plurality of maximum response
axes aligned in a respective second plurality of directions in the
x-y plane, wherein the first plurality of directions and the second
plurality of directions comprise the same plurality of directions
or different pluralities of directions; selecting ones of the first
plurality of magnetic field signals and selecting ones of the
second plurality of magnetic field signals; processing the selected
ones of the first plurality of magnetic field signals and the
selected ones of the second plurality of magnetic field signals to
generate at least one sequential signal; and processing the at
least one sequential signal to generate an x-y angle signal
indicative of a direction of the magnetic field in the x-y
plane.
26. The method of claim 25, wherein the at least one sequential
signal comprises a first sequential signal and a second sequential
signal different than the first sequential signal, and wherein the
processing comprises: generating a combined sequential signal as a
sum or a difference of a first signal representative of the first
sequential signal and a second signal representative of the second
sequential signal.
27. The method of claim 25, wherein the at least one sequential
signal comprises a first sequential signal and a second sequential
signal different than the first sequential signal, and wherein the
processing comprises: generating a combined sequential signal as a
product of a first signal representative of the first sequential
signal and a second signal representative of the second sequential
signal.
28. The method of claim 25, wherein the first plurality of magnetic
field sensing elements comprises a first CVH element, wherein the
second plurality of magnetic field sensing elements comprises a
second CVH element different than the first CVH element.
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, more particularly, to a magnetic field sensor that has at
least two CVH elements (or at least two pluralities of magnetic
field sensing elements) operating in concert.
BACKGROUND
[0004] Magnetic field sensors can be used in a variety of
applications. In one application, a magnetic field sensor can be
used to detect a direction of a magnetic field, i.e., and angle of
the direction of the magnetic field. In another application, a
magnetic field sensor can be used to sense an electrical current.
One type of current sensor uses a Hall Effect magnetic field
sensing element in proximity to a current-carrying conductor.
[0005] Planar Hall elements and vertical Hall elements are known
types of magnetic field sensing elements 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.
[0006] 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 Hall elements, is
known and described in PCT Patent Application No. PCT/EP2008056517,
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 element is a circular arrangement
of a plurality of vertical Hall elements arranged over a common
circular implant region in a substrate, and without barriers to
flow of electrical current among the vertical Hall elements. The
CVH element can be used to sense a direction (i.e., an angle) (and
optionally, an amplitude) of a magnetic field in a plane of the
substrate.
[0007] Various parameters characterize the performance of magnetic
field sensing elements and magnetic field sensors that use 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] The above-described CVH 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
element can be used to provide an output signal representative of
an angle of rotation of the target object.
[0009] The CVH element provides output signals from a plurality of
vertical Hall elements from which it is constructed. Each vertical
Hall element can have an undesirable and different DC offset.
[0010] The CVH element is but one sensing element that can provide
an output signal representative of an angle of a magnetic field,
i.e., an angle sensor. For example, an angle sensor can be provided
from a plurality of separate vertical Hall elements or a plurality
of magnetoresistance elements.
[0011] A CVH element has an operation limit at which it can sample
vertical Hall elements in the CVH element to identify a direction
of the magnetic field. The limit is related to how fast electronic
circuits coupled to the CVH element, i.e., how fast a CVH magnetic
field sensor that has a CVH element, can take sequential samples
around the ring of vertical Hall elements, e.g., thirty-two or
sixty-four vertical Hall elements. This limit is of particular
interest when the magnetic field is rotating. In order to
accurately identify a direction of a rotating magnetic field, a
rate at which the CVH magnetic field sensor sequentially samples
all the vertical Hall elements of the CVH element must be much
higher than the rate of rotation of the magnetic field. It would be
desirable to provide a magnetic field sensor forming an angle
sensor that can operate at higher sampling rates and that can sense
a more rapidly rotating magnetic field.
[0012] In addition, using, for example, sixty-four vertical Hall
elements in a CVH element and a non-rotating magnetic field, a
basic angular resolution is about 5.6 degrees (three hundred sixty
divided by sixty-four). It would be desirable to provide a magnetic
field sensor forming an angle sensor with a higher resolution
(i.e., a smaller basic angle of resolution.)
SUMMARY
[0013] The present invention can provide a magnetic field sensor
forming an angle sensor that can operate at higher sampling rates
and that can sense a more rapidly rotating magnetic field.
[0014] The present invention can also provide a magnetic field
sensor forming an angle sensor with a higher resolution (i.e., a
smaller basic angle of resolution.)
[0015] In accordance with an example useful for understanding an
aspect of the present invention, a magnetic field sensor for
sensing a direction of a magnetic field in an x-y plane, can
include a first plurality of magnetic field sensing elements
operable to generate a first plurality of magnetic field signals,
the first plurality of magnetic field sensing elements having a
respective first plurality of maximum response axes aligned in a
respective first plurality of different directions in the x-y
plane. The magnetic field sensor can also include a second
plurality of magnetic field sensing elements operable to generate a
second plurality of magnetic field signals different than the first
plurality of magnetic field signals, the second plurality of
magnetic field sensing elements having a respective second
plurality of maximum response axes aligned in a respective second
plurality of directions in the x-y plane, wherein the first
plurality of directions and the second plurality of directions
comprise the same plurality of directions or different pluralities
of directions. The magnetic field sensor can also include at least
one sequence switches circuit operable to select ones of the first
plurality of magnetic field signals and to select ones of the
second plurality of magnetic field signals. The magnetic field
sensor can also include a processing circuit operable to combine
the selected ones of the first plurality of magnetic field signals
and the selected ones of the second plurality of magnetic field
signals to generate at least one sequential signal and to process
the at least one sequential signal generate an x-y angle signal
indicative of a direction of the magnetic field in the x-y
direction.
[0016] In accordance with another example useful for understanding
another aspect of the present invention, a method of sensing a
direction of a magnetic field in an x-y plane comprises generating
a first plurality of magnetic field signals with a first plurality
of magnetic field sensing elements, the first plurality of magnetic
field sensing elements having a respective first plurality of
maximum response axes aligned in a respective first plurality of
different directions in the x-y plane. The method can also include
generating a second plurality of magnetic field signals different
than the first plurality of magnetic field signals with a second
plurality of magnetic field sensing elements, the second plurality
of magnetic field sensing elements having a respective second
plurality of maximum response axes aligned in a respective second
plurality of directions in the x-y plane, wherein the first
plurality of directions and the second plurality of directions
comprise the same plurality of directions or different pluralities
of directions. The method can also include selecting ones of the
first plurality of magnetic field signals and selecting ones of the
second plurality of magnetic field signals. The method can also
include processing the selected ones of the first plurality of
magnetic field signals and the selected ones of the second
plurality of magnetic field signals to generate at least one
sequential signal. The method can also include processing the at
least one sequential signal to generate an x-y angle signal
indicative of a direction of the magnetic field in the x-y
direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] 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:
[0018] 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 circular implant region upon a
substrate, and a two pole magnet disposed close to the CVH
element;
[0019] FIG. 1A is a pictorial showing a plurality of magnetic field
sensing elements;
[0020] FIG. 2 is a graph showing an output signal as may be
generated by the CVH element of FIG. 1 or by the plurality of
magnetic field sensing elements of FIG. 1A;
[0021] FIG. 3 is a pictorial showing two circular vertical Hall
(CVH) sensing elements arranged concentrically, each having a
respective plurality of vertical Hall elements, each arranged in a
respective circle over a respective common circular implant region
upon a substrate, a relative rotation angle between the two
circular vertical Hall (CVH) sensing elements;
[0022] FIG. 3A is a pictorial showing another two circular vertical
Hall (CVH) sensing elements arranged concentrically, each having a
respective plurality of vertical Hall elements, each arranged in a
respective circle over a respective common circular implant region
upon a substrate, a different relative rotation angle between the
two circular vertical Hall (CVH) sensing elements;
[0023] FIG. 3B is a pictorial showing two circular vertical Hall
(CVH) sensing elements arranged non-concentrically, each having a
respective plurality of vertical Hall elements, each arranged in a
respective circle over a respective common circular implant region
upon a substrate, a relative rotation angle between the two
circular vertical Hall (CVH) sensing elements;
[0024] FIG. 3C is a pictorial showing another two circular vertical
Hall (CVH) sensing elements arranged non-concentrically, each
having a respective plurality of vertical Hall elements, each
arranged in a respective circle over a respective common circular
implant region upon a substrate, a different relative rotation
angle between the two circular vertical Hall (CVH) sensing
elements;
[0025] FIG. 4 is a block diagram showing a magnetic field sensor
that can have the two circular vertical Hall (CVH) sensing elements
of FIGS. 3-3C;
[0026] FIG. 4A is a block diagram showing another magnetic field
sensor that can have the two circular vertical Hall (CVH) sensing
elements of FIGS. 3-3C; and
[0027] FIG. 4B is a block diagram showing another magnetic field
sensor that can have the two circular vertical Hall (CVH) sensing
elements of FIGS. 3-3C.
DETAILED DESCRIPTION
[0028] The features and other details of the concepts, systems, and
techniques sought to be protected herein are more particularly
described below. It should be understood that any specific
embodiments described herein are shown by way of illustration and
not as limitations. The principal features described herein can be
employed in various embodiments without departing from the scope of
the concepts sought to be protected. Embodiments described herein
and associated advantages may be best understood by referring to
the drawings, where like numerals are used for like and
corresponding parts throughout the various views.
[0029] 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 element can be, but is
not limited to, a Hall effect element, a magnetoresistance element,
or a magnetotransistor. As is known, there are different types of
Hall effect elements, for example, a planar Hall element, a
vertical Hall element, and a Circular Vertical Hall (CVH) element.
As is also known, there are different types of magnetoresistance
elements, for example, a semiconductor magnetoresistance element
such as Indium Antimonide (InSb), a giant magnetoresistance (GMR)
element, for example, a spin valve, an anisotropic
magnetoresistance element (AMR), a tunneling magnetoresistance
(TMR) element, and a magnetic tunnel junction (MTJ). The magnetic
field sensing element may be a single element or, alternatively,
may include two or more magnetic field sensing elements arranged in
various configurations, e.g., a half bridge or full (Wheatstone)
bridge. Depending on the device type and other application
requirements, the magnetic field sensing element may be a device
made of a type IV semiconductor material such as Silicon (Si) or
Germanium (Ge), or a type III-V semiconductor material like
Gallium-Arsenide (GaAs) or an Indium compound, e.g.,
Indium-Antimonide (InSb).
[0030] 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 metal based or metallic
magnetoresistance elements (e.g., GMR, TMR, AMR) and vertical Hall
elements tend to have axes of sensitivity parallel to a
substrate.
[0031] As used herein, the term "magnetic field sensor" is used to
describe a circuit that uses a magnetic field sensing element,
generally in combination with other circuits. 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 or a
ferromagnetic target (e.g., gear teeth) where the magnetic field
sensor is used in combination with a back-biased or other magnet,
and a magnetic field sensor that senses a magnetic field density of
a magnetic field.
[0032] The terms "parallel" and "perpendicular" are used in various
contexts herein. It should be understood that the terms parallel
and perpendicular do not require exact perpendicularity or exact
parallelism, but instead it is intended that normal manufacturing
tolerances apply, which tolerances depend upon the context in which
the terms are used. In some instances, the term "substantially" is
used to modify the terms "parallel" or "perpendicular." In general,
use of the term "substantially" reflects angles that are beyond
manufacturing tolerances, for example, within +/-ten degrees.
[0033] As used herein, the term "baseline" and the phrase "baseline
level" are used to describe a lowest magnitude (which may be near
zero or may be some other magnetic field) of a magnetic field
experienced by a magnetic field sensing element within a magnetic
field sensor when the magnetic field sensor is operating in a
system.
[0034] As used herein, the term "processor" is used to describe an
electronic circuit that performs a function, an operation, or a
sequence of operations. The function, operation, or sequence of
operations can be hard coded into the electronic circuit or soft
coded by way of instructions held in a memory device. A "processor"
can perform the function, operation, or sequence of operations
using digital values or using analog signals.
[0035] In some embodiments, the "processor" can be embodied in an
application specific integrated circuit (ASIC), which can be an
analog ASIC or a digital ASIC. In some embodiments, the "processor"
can be embodied in a microprocessor with associated program memory.
In some embodiments, the "processor" can be embodied in a discrete
electronic circuit, which can be an analog or digital.
[0036] As used herein, the term "module" is used to describe a
"processor."
[0037] A processor can contain internal processors or internal
modules that perform portions of the function, operation, or
sequence of operations of the processor. Similarly, a module can
contain internal processors or internal modules that perform
portions of the function, operation, or sequence of operations of
the module.
[0038] While electronic circuits shown in figures herein may be
shown in the form of analog blocks or digital blocks, it will be
understood that the analog blocks can be replaced by digital blocks
that perform the same or similar functions and the digital blocks
can be replaced by analog blocks that perform the same or similar
functions. Analog-to-digital or digital-to-analog conversions may
not be explicitly shown in the figures, but should be
understood.
[0039] In particular, it should be understood that a so-called
comparator can be comprised of an analog comparator having a two
state output signal indicative of an input signal being above or
below a threshold level (or indicative of one input signal being
above or below another input signal). However, the comparator can
also be comprised of a digital circuit having an output signal with
at least two states indicative of an input signal being above or
below a threshold level (or indicative of one input signal being
above or below another input signal), respectively, or a digital
value above or below a digital threshold value (or another digital
value), respectively.
[0040] As used herein, the term "predetermined," when referring to
a value or signal, is used to refer to a value or signal that is
set, or fixed, in the factory at the time of manufacture, or by
external means, e.g., programming, thereafter. As used herein, the
term "determined," when referring to a value or signal, is used to
refer to a value or signal that is identified by a circuit during
operation, after manufacture.
[0041] As used herein, the term "active electronic component" is
used to describe an electronic component that has at least one p-n
junction. A transistor, a diode, and a logic gate are examples of
active electronic components. In contrast, as used herein, the term
"passive electronic component" as used to describe an electronic
component that does not have at least one p-n junction. A capacitor
and a resistor are examples of passive electronic components.
[0042] As used herein, the terms "line" and "linear" are used to
describe either a straight line or a curved line. The line can be
described by a function having any order less than infinite.
[0043] Referring to FIG. 1, a circular vertical Hall (CVH) element
112 includes a circular implant and diffusion region 118 in a
substrate (not shown). The CVH element 112 has a plurality of
vertical Hall elements, of which a vertical Hall element 112a is
but one example. In some embodiments, the common implant and
diffusion region 118 can be characterized as a common epitaxial
region upon a substrate, bounded by semiconductor isolation
structures.
[0044] Each vertical Hall element has a plurality of Hall element
contacts (e.g., four or five contacts), e.g., 112aa. Each vertical
Hall element contact can be comprised of a metal contact over a
contact diffusion region (a pickup) diffused into the common
implant and diffusion region 118.
[0045] A particular vertical Hall element (e.g., 112a) within the
CVH element 112, 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., 112b). 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., thirty-two or
sixty-four. 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 element.
[0046] As shown, a center of a vertical Hall element 0 can
positioned along an x-axis 120 and a center of vertical Hall
element 118 can be positioned along a y-axis 122. In the exemplary
CVH element 112, 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.
[0047] In some applications, a circular magnet 114 having a north
side 114b and a south side 114a can be disposed over the CVH 112.
The circular magnet 114 tends to generate a magnetic field 116
having a direction from the north side 114b to the south side 114a,
here shown to be pointed to a direction of about forty-five degrees
relative to x-axis 120.
[0048] In some applications, the circular magnet 114 is
mechanically coupled to a rotating target object, for example, an
automobile steering shaft of an automobile camshaft, and is subject
to rotation relative to the CVH element 112. With this arrangement,
the CVH element 112, in combination with an electronic circuit
described below, can generate a signal related to the angle of
rotation of the magnet 114, i.e., an angle of rotation of the
target object to which the magnet is coupled.
[0049] While the circular magnet 114 is shown, it should be
appreciated that other magnets or other magnetic fields can be
used, and, more generally, the CVH element 112 is operable to
identify an angle of a magnetic field in a plane of the CVH element
112.
[0050] Referring now to FIG. 1A, a plurality of magnetic field
sensing elements 130a-130h, in a general case, can be any type of
magnetic field sensing elements. The magnetic field sensing
elements 130a-130h can be, for example, separate vertical Hall
elements or separate magnetoresistance elements, each having an
axis of maximum response parallel to a surface of a substrate 34,
each pointing in a different direction in the plane of the surface.
These magnetic field sensing elements can be coupled to an
electronic circuit the same as or similar to electronic circuits
described below in conjunction with FIGS. 3 and 6. There can also
be a magnet the same as or similar to the magnet 114 of FIG. 1
disposed proximate to the magnetic field sensing elements
130a-130h.
[0051] Referring now to FIG. 2, a graph 200 has a horizontal axis
with a scale in units of CVH vertical Hall element position, n,
around a CVH element, for example, the CVH element 112 of FIG. 1.
The graph 200 also has a vertical axis with a scale in amplitude in
units of millivolts. The vertical axis is representative of output
signal levels from the plurality of vertical Hall elements of the
CVH element taken sequentially, one at a time, about the ring of
contacts of the CVH element.
[0052] The graph 200 includes a signal 202 representative of output
signal levels from the plurality of vertical Hall elements of the
CVH taken with the magnetic field of FIG. 1 pointing in a direction
of forty-five degrees.
[0053] Referring briefly to FIG. 1, as described above, vertical
Hall element 0 is centered along the x-axis 120 and vertical Hall
element 8 is centered along the y-axis 122. In the exemplary CVH
element 112, 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. In other embodiments, there
are sixty-four vertical Hall element contacts and a corresponding
sixty-four vertical Hall elements.
[0054] In FIG. 2, for the magnetic field 116 pointing at positive
forty-five degrees, a maximum positive signal is achieved from a
vertical Hall element centered at position 4, which is aligned with
the magnetic field 116 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 116 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.
[0055] A sine wave 204 is provided to more clearly show ideal
behavior of the signal 202. The signal 202 has variations due to
vertical Hall element offsets, which tend to cause corresponding
variations of output signals causing them to be too high or too low
relative to the sine wave 204, in accordance with offset errors for
each element. The offset signal errors are undesirable.
[0056] Full operation of the CVH element 112 of FIG. 1 and
generation of the signal 202 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.
[0057] Groups of contacts of each vertical Hall element can be used
in a chopped arrangement (also referred to herein as current
spinning) 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 element 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.
[0058] Each step of the signal 202 is representative of an
unchopped output signal, i.e., from one respective group of
vertical Hall element contacts, i.e., from one respective vertical
Hall element. Thus, for a CVH element having 32 vertical Hall
elements taken sequentially, there are thirty-two steps in the
signal 202 when current spinning is not used. However, for
embodiments in which current spinning is used or in which a current
swapping operation is performed, each step of the signal 202 can be
comprised of several sub-steps (not shown, e.g., two sub-steps or
four sub-steps). Each sub-step may, for example, be indicative of a
current spinning "phase" in embodiments where current spinning is
used.
[0059] Current spinning and current spinning phases are not
described herein in detail, but should be understood.
[0060] It will be understood that a phase of the signal 202 is
related to an angle of the magnetic field 116 of FIG. 1 relative to
position zero of the CVH element 112. It will also be understood
that a peak amplitude of the signal 202 is generally representative
of a strength of the magnetic field 116. Using electronic circuit
techniques described above in PCT Patent Application No.
PCT/EP2008/056517, or using other techniques described below, a
phase of the signal 202 (e.g., a phase of the signal 204) can be
found and can be used to identify the pointing direction of the
magnetic field 116 of FIG. 1 relative to the CVH element 112.
[0061] It should be understood that the phase of the signal 202,
used to identify an angle of a detected magnetic field in a plane
of the CVH element, can be determined in a number of ways. With
some ways, it is necessary to achieve and entire cycle of the
signal 202 before the angle of the magnetic field can be
determined. Thus, it may be desirable to have a frequency of the
signal 202 as high as possible. However, higher frequencies also
tend to use more power.
[0062] The signal 202 is also referred to herein as a "sequential
signal" 202, which will be understood to be comprised of sequential
ones of a plurality of magnetic field signals or "steps," each
magnetic field signal generated by a respective one of a plurality
of magnetic field sensing elements, e.g., the plurality of vertical
Hall elements within a CVH element. While the sequential signal 202
is shown to be an analog signal having analog voltage steps, it
should be understood that an equivalent digital sequential signal
can be generated merely by analog-to-digitally converting the
analog sequential signal.
[0063] Circuits described below can make use of two or more CVH
elements coupled to electronic circuits to identify at least a
phase, and therefore, an angle of a magnetic field in a plane, the
phase being a phase of a CVH element signal like the CVH element
signal 202 of FIG. 2. However, in other embodiments, the two or
more CVH elements can be replaced by respective pluralities of
separate magnetic field sensing elements, for example, groups of
vertical Hall elements or groups of magnetoresistance elements.
[0064] Referring now to FIG. 3, a dual CVH element 300 can include
a first CVH element 302 disposed concentrically with a second CVH
element 308.
[0065] The first CVH element 302 can have an outer boundary 304 and
an inner boundary 306 between which a common circular implant and
diffusion region is formed and in which electrons can flow.
[0066] The second CVH element 308 can have an outer boundary 310
and an inner boundary 312 between which a common circular implant
and diffusion region is formed and in which electrons can flow.
[0067] Regions 314, 316, 318 can be barrier regions formed by deep
diffusions into an epi layer in which the first and second CVH
element 302, 308 are also formed. The regions 314, 316, 318
effectively block the flow of electrons.
[0068] As used herein, the term "contact" is used to describe a
metallized connection of a semiconductor structure, for example,
metal plating forming a contact. In turn, a contact provides a low
resistance electrical coupling to a pickup, which is a diffusion
into the semiconductor structure.
[0069] The first CVH element 302 can include a plurality of
contacts, and associate pickups thereunder, of which a contact 354
is but one example. There can be any number of contacts in the
first CVH element 302, for example, thirty-two or sixty-four
contacts. The number of contacts is selected in accordance with a
desired basic angular resolution of the CVH element and in
accordance with a desired small diameter of the CVH element.
[0070] Similarly, the second CVH element 308 can include a
plurality of contacts, and associate pickups thereunder, similar to
the contact 324. There can be any number of contacts in the second
CVH element 308, for example, thirty-two or sixty-four contacts.
The number of contacts is selected in accordance with a desired
basic angular resolution of the CVH element and in accordance with
a desired small diameter of the CVH element.
[0071] In some embodiments, there can be the same number of
contacts in the first and second CVH elements 302, 308.
[0072] The first CVH element 302 can include a plurality of
vertical Hall elements, e.g., 320, 322, which can each contain a
plurality of vertical Hall element contacts.
[0073] Similarly, the second CVH element 308 can include a
plurality of vertical Hall elements, e.g., 326, 328, which can each
contain a plurality of vertical Hall element contacts.
[0074] As typified by the graph 200 of FIG. 2, first sequential
samples can be taken from the plurality of vertical Hall elements
of the first CVH element 302 and second sequential samples can be
taken from the plurality of vertical Hall elements of the second
CVH element 308. The first and second sequential samples can be
taken in different ways.
[0075] In some embodiments, vertical Hall elements of the first and
second CVH elements 302, 308 can be sampled separately to generate
two sequential signals with samples taken at the same time from the
first and second CVH elements 302, 308 described more fully below
in conjunction with FIG. 4. In other embodiments, vertical Hall
elements of the first and second CVH elements 302, 308 can be
sampled in an interleaved fashion described more fully below in
conjunction with FIGS. 4A and 4B.
[0076] For embodiments that sample the vertical Hall elements of
the first and second CVH elements 302, 308 separately, the
resulting sequential signals (see, e.g., signal 202 of FIG. 2) can
be at any relative phase versus CVH element position.
[0077] In a first sequencing embodiment, the first CVH element 302
and second CVH element 308 can generate samples in the following
order:
[0078] time 1 vertical Hall elements centered at contacts 336,
338
[0079] time 2 vertical Hall elements centered at contacts 340,
342
[0080] time 3 vertical Hall elements centered at contacts 344,
346
[0081] time 4 vertical Hall elements centered at contacts 348, 350;
and so on around the CVH elements 302, 308.
[0082] In the first sequencing embodiment, successive samples
generated by the first and second CVH elements 302, 308 can
continue around the first and second CVH elements 302, 308 such
that vertical Hall elements of the first and second CVH elements
302, 308 remain aligned with each other during the sequencing
around the first and second CVH elements 302, 308.
[0083] The first sequencing embodiment may take more power than for
a signal CVH element alone, since two vertical Hall elements are
powered on at the same time. However, with the first sequencing
embodiment, combining of sequential samples generated by the first
and second CVH elements 302, 308, in particular, adding or
subtracting first and second sequential samples from aligned
vertical Hall elements to generate a combined sequential signal
(similar to sequential signal 202 of FIG. 2), can result in
improvements described below.
[0084] Equation (1) is indicative of an improvement described below
associated with the first sequencing embodiment:
(A*sin(.omega.t)+Off1)+(B*sin(.omega.t)+Off2)=(A+B)*sin(.omega.t)+(Off1+-
Off2) (1)
where: Off1 and Off2 are DC offset voltages associated with
vertical Hall elements of the first and second CVH element 302,
308, respectively.
[0085] It should be understood that, in the first sequencing
embodiment, a resulting signal amplitude, A+B, is greater than an
amplitude, A or B, from either of the CVH sensing elements 302, 308
alone. However, electrical noise is only increased by a factor of
sqrt (2). Thus, the signal to noise ratio is improved in the first
sequencing embodiment.
[0086] In a second sequencing embodiment, the first CVH element 302
and second CVH element 308 can generate samples in the following
order:
[0087] time 1 vertical Hall elements centered at contacts 336,
362
[0088] time 2 vertical Hall elements centered at contacts 340,
364
[0089] time 3 vertical Hall elements centered at contacts 344,
366
[0090] time 4 vertical Hall elements centered at contacts 348, 368,
and so on around the CVH elements 302, 308.
[0091] In the second sequencing embodiment, successive samples
generated by the first and second CVH elements 302, 308 can
continue around the first and second CVH elements 302, 308 such
that centers of vertical Hall elements of the first and second CVH
element s 302, 308 remain offset by a relative one hundred eighty
degrees during the sequencing of the first and second CVH elements
302, 308. In the second sequencing embodiment, sequential signals
(see, e.g., sequential signal 202 of FIG. 2) generated by the first
and second CVH elements 302, 308 can be approximately one hundred
eighty degrees apart relative to each other.
[0092] Equation (2) is indicative of improvements described below
associated with the second sequencing embodiment:
[A*sin(.omega.t)+Off1]-[B*sin(.omega.t+180)+Off2]=[(A+B)*sin(.omega.t)]+-
(Off1-Off2) (2)
[0093] It should be understood that, like in the first sequencing
embodiment, in the second sequencing embodiment, resulting signal
amplitude is A+B is greater than an amplitude A or B from either of
the CVH sensing elements 304, 308 alone. However, electrical noise
is only increased by a factor of sqrt (2). Thus, the signal to
noise ratio is improved in the second sequencing embodiment.
[0094] In a third sequencing embodiment, the first CVH element 302
and second CVH element 308 can generate samples in the following
order:
[0095] time 1 vertical Hall elements centered at contacts 336,
354
[0096] time 2 vertical Hall elements centered at contacts 340,
356
[0097] time 3 vertical Hall elements centered at contacts 344,
358
[0098] time 4 vertical Hall elements centered at contacts 348, 360,
and so on around the CVH elements 302, 308.
[0099] In the third sequencing embodiment, successive samples
generated by the first and second CVH elements 302, 308 can
continue around the first and second CVH elements 302, 308 such
that centers of vertical Hall elements of the first and second CVH
element s 302, 308 remain offset by a relative ninety degrees
during the sequencing of the first and second CVH elements 302,
308. In the third sequencing embodiment, sequential signals (see,
e.g., sequential signal 202 of FIG. 2) generated by the first and
second CVH elements 302, 308 can be approximately ninety degrees
apart relative to each other.
[0100] Equation (3) is indicative of an improvement described below
associated with the third sequencing embodiment.
= [ A * sin ( .omega. t ) + Off 1 ] * [ B * cos ( .omega. t ) + Off
2 ] = [ ( A * B / 2 ) * sin ( 2 .omega. t ) ] + [ A * Off 2 * sin (
.omega. t ) ] + [ B * Off 1 * cos ( .omega. t ) ] + [ Off 1 * Off 2
] ( 3 ) ##EQU00001##
[0101] With the third sequencing embodiment, combining of
sequential samples generated by the first and second CVH elements
302, 308, in particular, multiplying associated first and second
sequential signals, can result in a combined sequential signal at
twice the fundamental frequency (2 .omega.t) of one sequential
signal alone from one CVH element. Recall from discussion above in
conjunction with FIG. 2, that for some arrangements it is necessary
to achieve an entire cycle of a sequential signal, e.g., the signal
202 of FIG. 2, in order to identify a detected angle of a magnetic
field. Thus, the combined sequential signal at twice the
fundamental frequency of one CVH element alone can result in faster
measurement of a magnetic field direction.
[0102] While first, second, and third sequencing embodiments
described above take pairs of samples from the first and second CVH
elements 302, 308 at the same time, in other similar sequencing
embodiments, samples are taken from the first and second CVH
elements 302, 308 sequentially at different times, i.e., one
vertical Hall element can be powered on at a time. The sequential
arrangements can result in power consumption over each full
sequence around the CVH element 302, 308 being approximately the
same as that achieved with each full sequence around one CVH
element.
[0103] In a fourth sequencing embodiment, the first CVH element 302
and second CVH element 308 can generate samples in the following
order:
[0104] time 1 vertical Hall element centered at contact 336
[0105] time 2 vertical Hall element centered at contact 342
[0106] time 3 vertical Hall element centered at contact 344
[0107] time 4 vertical Hall element centered at contact 350; and so
on around the CVH elements 302, 308.
[0108] In the fourth sequencing embodiment, successive samples
generated by the first and second CVH elements 302, 308 can
continue around the first and second CVH elements 302, 308 such
that centers of vertical Hall elements of the first and second CVH
elements 302, 308 sequence in the same angular steps, alternating
between the first CVH element 302 and the second CVH element
308.
[0109] Sampling speed around the first and second CVH elements 302,
308 may be greater than for one CVH element alone, because, while a
vertical Hall element of one CVH element is being sampled, a
vertical Hall element of the other CVH element can be charging to
prepare for a next sample, back and forth between the two CVH
elements 302, 308. In addition, an angular resolution may be
improved relative to one CVH element.
[0110] Referring now to FIG. 3A, in which like elements of FIG. 3
have like reference designations, a dual CVH element 370 includes
the first CVH element 302 disposed concentrically with a second CVH
element 308'. The second CVH element 308' is similar to the CVH
element 308 of FIG. 3. However, contacts of the second CVH element
308' are rotated from contacts of the first CVH element 302 by one
half of a separation of contacts (i.e., one half of an angle
between contacts) of the first and second CVH elements 302, 308' as
represented by arrow 332. Other relative angular separations are
also possible.
[0111] While the arrangement of FIG. 3A can be used in ways similar
to any of the sequencing embodiments described above as sequencing
embodiments one through four, this arrangement is particularly
suited for a fifth sequencing embodiment.
[0112] In the fifth sequencing embodiment, the first CVH element
302 and second CVH element 308 can generate samples in the
following order:
[0113] time 1 vertical Hall element 336
[0114] time 2 vertical Hall element 372
[0115] time 3 vertical Hall element 340
[0116] time 4 vertical Hall element 374; and so on around the CVH
elements 302, 308'.
[0117] The fifth sequencing embodiment can achieve a higher basic
angular resolution of measured magnetic fields, roughly half the
basic angular resolution of one of the CVH elements 302, 308'
alone. Sampling speed around the first and second CVH elements 302,
308' may be slower than for the fourth sequencing embodiment above,
because, while the fourth sequencing embodiment essentially uses
every other contact of each one of the CVH elements 302, 308, the
fifth sequencing embodiment uses every contact.
[0118] Referring now to FIG. 3B, a dual CVH element 380 includes a
first CVH element 381 disposed non-concentrically with a second CVH
element 387.
[0119] The first CVH element 381 can have an outer boundary 382 and
an inner boundary 383 between which a common circular implant and
diffusion region is formed and in which electrons can flow.
[0120] The second CVH element 387 can have an outer boundary 388
and an inner boundary 389 between which a common circular implant
and diffusion region is formed and in which electrons can flow.
[0121] Regions 385, 386, 390, 391 can include barrier regions
formed by deep diffusions into an epi layer in which the first and
second CVH elements 381, 387 are also formed. The regions 385, 386,
390, 391 effectively block the flow of electrons.
[0122] The first and second CVH elements 381, 387 can each have a
respective plurality of contacts, typified by small rectangular
boxes. As described above in conjunction with FIG. 3, the plurality
of contacts can be arranged as a plurality of vertical Hall
elements, each having, for example, five contacts.
[0123] It should be apparent that the first CVH element 381 is like
the first CVH element 302 of FIG. 3 and the second CVH element 387
is like the second CVH element 308 of FIG. 3 (i.e., aligned
contacts). Thus, sequencing embodiments one through four described
above in conjunction with FIG. 3 apply also to the dual CVH element
380. The same advantages also apply.
[0124] It may be advantageous that the first and second CVH
elements 381, 387 be in close proximity so that they can sense
substantially the same magnetic field direction. However, in other
embodiments, the first and second CVH elements 381, 387 can be
separated by a larger predetermined distance so that they do not
sense essentially the same magnetic fields, and the signals from
the CVH element 381, 387 can be combined in a differential
arrangement.
[0125] In some embodiments, the first and second CVH elements 381,
387 can have the same diameter. However, in other embodiments, one
of the first or second CVH elements 381, 387 can have a diameter
smaller than the other.
[0126] Referring now to FIG. 3C, a dual CVH element 380' includes
the first CVH element 381 of FIG. 3B disposed non-concentrically
with a second CVH element 387', which is similar to the second CVH
element 387 of FIG. 3B. Contacts of the second CVH element 387' are
rotated from contacts of the first CVH element 381 and from
contacts of the second CVH element 387 of FIG. 3B by one half of a
separation of contacts (i.e., one half of an angle between
contacts) of the first and second CVH elements 381, 387 as
represented by arrow 392. Other relative angular separations are
also possible.
[0127] The second CVH element 387' can have an outer boundary 388'
and an inner boundary 389', between which a common circular implant
and diffusion region is formed and in which electrons can flow.
[0128] Regions 385, 386, 390, 391 can include barrier regions
formed by deep diffusions into an epi layer in which the first and
second CVH element 302, 308 are also formed. The regions 385, 386,
390, 391 effectively block the flow of electrons.
[0129] The first and second CVH elements 381, 387' can each have a
respective plurality of contacts, typified by small rectangular
boxes. As described above in conjunction with FIG. 3, the plurality
of contacts can be arranged as a plurality of vertical Hall
elements, each having, for example, five contacts.
[0130] It should be apparent that the first CVH element 381 is like
the first CVH element 302 of FIG. 3A and the second CVH element
387' is like the second CVH element 308' of FIG. 3A (i.e., contacts
are offset by half a distance (or half and angle) between
contacts). Thus, the fifth sequencing embodiment described above in
conjunction with FIG. 3A applies also to the dual CVH element 380'.
The same advantages also apply.
[0131] It may be advantageous that the first and second CVH
elements 381, 387' be in close proximity so that they can sense
substantially the same magnetic field direction.
[0132] In some embodiments, the first and second CVH elements 381,
387' can have the same diameter. However, in other embodiments, one
of the first or second CVH elements 381, 387' can have a diameter
smaller than the other.
[0133] While dual CVH elements are described above, in other
embodiments, there can be more than two CVH elements, operating in
a similar way to the sequencing embodiments described above as
sequencing embodiments one through five.
[0134] Magnetic field sensors are described below that have dual
CVH elements (but which can include more than two CVH elements in
other embodiments). The dual CVH elements can be any of the dual
CVH elements of FIG. 3, 3A, 3B, or 3C. Any of the sequencing
embodiments described above as sequencing embodiments one through
five can be used. Other sequencing embodiments are also
possible.
[0135] Referring now to FIG. 4, a magnetic field sensor 400 can
include a first CVH element 402 and a second CVH element 430,
considered together to be a dual CVH element. The first CVH element
402 can be coupled to receive current signals 426a from a current
sources and switches module 426 operable to provide a current to
sequential ones of vertical Hall elements within the first CVH
element 402. The second CVH element 430 can be coupled to receive
current signals 428a from a current sources and switches module 428
operable to provide a current to sequential ones of vertical Hall
elements within the second CVH element 430.
[0136] The current sources and switches modules 426, 428 can be
coupled to receive a clock signal 438a from an oscillator and logic
module 438. A rate of the clock signal 438a can determine a rate at
which the vertical Hall elements within the first and second CVH
elements 402, 430 sequence around the rings.
[0137] A physical coupling 402a couples the first CVH element 402
to a sequences switches and chopping switches module 404. The
physical coupling 402a can couple all output nodes of the first CVH
element 402 to the sequences switches and chopping switches module
404, sequential ones of which are selected to provide a
differential sequential signal 404a, 404b. The sequences switches
and chopping switches module 404 can also perform chopping, also
referred to as current spinning. Chopping is described above in
conjunction with FIG. 2. The sequences switches and chopping
switches module 404 can generate the differential sequential signal
404a, 404b, which can be the same as or similar to the sequential
signal 202 of FIG. 2.
[0138] Similarly, a physical coupling 430a couples the second CVH
element 430 to a sequences switches and chopping switches module
432. The physical coupling 430a can couple all output nodes of the
second CVH element 430 to the sequences switches and chopping
switches module 432, sequential ones of which are selected to
provide a differential sequential signal 432. The sequences
switches and chopping switches module 432 can also perform
chopping, also referred to as current spinning. The sequences
switches and chopping switches module 432 can generate a
differential sequential signal 432a, 432b, which can be the same as
or similar to the sequential signal 202 of FIG. 2.
[0139] It will be apparent that the sequence switches and chopping
switches modules 404, 432 in combination with the current sources
and switches modules 426, 428 can generate the sequence described
above as the Second and third sequencing embodiments.
[0140] An amplifier 406 can receive the differential sequential
signal 404a, 404b and can generate an amplified signal 406a. A band
pass filter 408 can received the amplified signal 406a and can
generate a filtered signal 408a. An amplifier 434 can receive the
differential sequential signal 432a, 432b can generate and
amplified signal 434a. A band pass filter 436 can receive the
amplified signal 434a and can generate a filtered signal 436a. The
filtered signals 408a, 436a can be similar to the ideal signal 204
of FIG. 2.
[0141] A multiplication module 410 can receive the filtered signals
406a, 434a and can generate a multiplied, i.e., combined,
sequential signal 410a. The combined sequential signal 410a is also
referred to herein as a product signal 410a. It should be
understood that the multiplication module 410 can be used in the
above-described second and third sequencing embodiments in
combination with equation (3) above.
[0142] The combined sequential signal, at a higher frequency
according to equation (3) can be received by a band pass filtered
412 centered at the higher frequency and can generate a filtered
signal 412a. The filtered signals 412a can be similar to the ideal
signal 204 of FIG. 2, but at double the frequency.
[0143] A comparator 416 can receive the filtered signal 412a,
receive a DC threshold signal 414 and can generate a two-state
comparison signal 416a.
[0144] An angle calculation module 418 can receive the comparison
signal 416a, can receive clock signals 438b, 438c, and can identify
a relative phase of the comparison signal 416a, relative to one of
the clock signals 438b, 438c. It should be understood that the
relative phase is related to an angle of a sensed magnetic field in
a plane of the first and second CVH elements 402, 430 generated by
a magnet, for example, a circular magnet 440 coupled to a shaft 442
and operable to rotate.
[0145] The angle calculation module 418 can generate an angle
signal 418a comprising information about the angle of the sensed
magnetic field. In some embodiments, the angle signal 418a can have
a digital count value related to the sensed angle of the magnetic
field.
[0146] A rotation speed module 420 can be coupled to receive the
angle signal 418a and can be operable to generate a speed signal
420a indicative of a speed of movement, e.g., a speed of rotation,
of a magnetic field as may be generated by the rotating magnet
440.
[0147] A rotation direction module 422 can be coupled to receive
the angle signal 418a and can be operable to generate a direction
signal 422a indicative of a direction of movement, e.g., a
direction of rotation, of a magnetic field as may be generated by
the rotating magnet 440.
[0148] An output format module 424 can receive one or more of the
angle signal 418a, the speed signal 420a, or the direction signal
422a, and can generate an output signal 424a having one or more of
angle information, speed information, or direction information.
[0149] In an alternate embodiment, the multiplication module 410
can be replaced by a summing module 444 or a differencing module
446 in accordance with the above described first or second
sequencing embodiments.
[0150] Referring now to FIG. 4A, in which like elements of FIG. 4
are have like reference designations, a magnetic field sensor 450
can include the first CVH element 402 and the second CVH element
430, considered together to be a dual CVH element. The first CVH
element 402 can be coupled to receive current signals 452a from a
current sources and switches module 452 operable to provide a
current to sequential ones of vertical Hall elements within the
first CVH element 402. The second CVH element 430 can be coupled to
receive current signals 454a from a current sources and switches
module 454 operable to provide a current to sequential ones of
vertical Hall elements within the second CVH element 430.
[0151] The current sources and switches modules 452, 454 can be
coupled to receive a clock signal 468a from an oscillator and logic
module 468. A rate of the clock signal 468a can determine a rate at
which the vertical Hall elements within the first and second CVH
elements 402, 430 sequence around the rings.
[0152] A physical coupling 402a couples the first CVH element 402
to a sequences switches and chopping switches module 456. The
physical coupling 402a can couple all output nodes of the first CVH
element 402 to the sequences switches and chopping switches module
456.
[0153] Similarly, a physical coupling 430a couples the second CVH
element 430 to the sequences switches and chopping switches module
456. The physical coupling 430a can couple all output nodes of the
second CVH element 430 to the sequences switches and chopping
switches module 456.
[0154] The sequences switches and chopping switches module 456 can
generate a differential combined sequential signal 456a, 456b that
can include samples from both the first and second CVH elements
402, 430. The sequences switches and chopping switches module 456
can also perform chopping, also referred to as current spinning.
Chopping is described above in conjunction with FIG. 2. The
sequences switches and chopping switches module 456 can generate
the differential combined sequential signal 456a, 456b, which can
be the same as or similar to the sequential signal 202 of FIG.
2.
[0155] It will be apparent that the sequence switches and chopping
switches modules 452, 454 in combination with the current sources
and switches module 456 can generate various ones of the sequences
described above as first, fourth, or fifth sequencing
embodiments.
[0156] An amplifier 458 can receive the differential combined
sequential signal 456a, 456b and can generate an amplified signal
454a. A band pass filter 460 can received the amplified signal 458a
and can generate a filtered signal 460a. The filtered signal 460a
can be similar to the ideal signal 204 of FIG. 2.
[0157] A comparator 462 can receive the filtered signal 460a,
receive a DC threshold signal 464, and can generate a two-state
comparison signal 462a.
[0158] An angle calculation module 464 can receive the comparison
signal 462a, can receive clock signals 468b, 468c, and can identify
a relative phase of the comparison signal 462a, relative to one of
the clock signals 468b, 468c. It should be understood that the
relative phase is related to an angle of a sensed magnetic field in
a plane of the first and second CVH elements 402, 430 generated by
a magnet, for example, the circular magnet 440 coupled to a shaft
442 and operable to rotate.
[0159] The angle calculation module 464 can generate an angle
signal 464a comprising information about the angle of the sensed
magnetic field. In some embodiments, the angle signal 464a can have
a digital count value related to the sensed angle of the magnetic
field.
[0160] The rotation speed module 420 can be coupled to receive the
angle signal 464a and can be operable to generate the speed signal
420a indicative of the speed of movement, e.g., the speed of
rotation, of a magnetic field as may be generated by the rotating
magnet 440.
[0161] The rotation direction module 422 can be coupled to receive
the angle signal 464a and can be operable to generate the direction
signal 422a indicative of a direction of movement, e.g., a
direction of rotation, of a magnetic field as may be generated by
the rotating magnet 440.
[0162] An output format module 466 can receive one or more of the
angle signal 464a, the speed signal 420a, or the direction signal
422a, and can generate an output signal 466a having one or more of
angle information, speed information, or direction information.
[0163] Referring now to FIG. 4B, in which like elements of FIG. 4
are have like reference designations, a magnetic field sensor 470
can include the first CVH element 402 and the second CVH element
430, considered together to be a dual CVH element. The first CVH
element 402 can be coupled to receive current signals 472a from a
current sources and switches module 472 operable to provide a
current to sequential ones of vertical Hall elements within the
first CVH element 402. The second CVH element 430 can be coupled to
receive current signals 474a from a current sources and switches
module 474 operable to provide a current to sequential ones of
vertical Hall elements within the second CVH element 430.
[0164] The current sources and switches modules 472, 474 can be
coupled to receive a clock signal 496a from an oscillator and logic
module 496. A rate of the clock signal 496a can determine a rate at
which the vertical Hall elements within the first and second CVH
elements 402, 430 sequence around the rings.
[0165] A physical coupling 402a couples the first CVH element 402
to a sequences switches and chopping switches module 476. The
physical coupling 402a can couple all output nodes of the first CVH
element 402 to a sequences switches and chopping switches module
476.
[0166] Similarly, a physical coupling 430a couples the second CVH
element 430 to the sequences switches and chopping switches module
476. The physical coupling 430a can couple all output nodes of the
second CVH element 430 to the sequences switches and chopping
switches module 476.
[0167] The sequences switches and chopping switches module 476 can
generate a differential sequential signal 476a, 476b that can
include samples from the first CVH elements 402. The sequences
switches and chopping switches module 476 can also generate a
differential sequential signal 476c, 476d that can include samples
from the second CVH elements 432. The sequences switches and
chopping switches module 476 can also perform chopping, also
referred to as current spinning. Chopping is described above in
conjunction with FIG. 2.
[0168] It will be apparent that the sequence switches and chopping
switches modules 476 in combination with the current sources and
switches modules 472, 474 can generate the sequence described above
as the third sequencing embodiment.
[0169] A multiplication module 478 can receive the differential
sequential signal 476a, 476b and the differential sequential signal
476c, 476d and can generate a multiplied, i.e., combined,
differential sequential signal 478a, 478b. The combined
differential sequential signal 478a, 478b is also referred to
herein as a product signal 478a, 478b. It should be understood that
the multiplication module 478 can be used in the above-described
third sequencing embodiment.
[0170] An amplifier 480 can receive the differential combined
sequential signal 478a, 478b and can generate an amplified signal
480a. A band pass filter 482 can received the amplified signal 480a
and can generate a filtered signal 482a. The filtered signal 482a
can be similar to the ideal signal 204 of FIG. 2, but at double the
frequency.
[0171] A comparator 484 can receive the filtered signal 482a,
receive a DC threshold signal 486, and can generate a two-state
comparison signal 484a.
[0172] An angle calculation module 488 can receive the comparison
signal 484a, can receive clock signals 496b, 496c, and can identify
a relative phase of the comparison signal 484a, relative to one of
the clock signals 496b, 496c. It should be understood that the
relative phase is related to an angle of a sensed magnetic field in
a plane of the first and second CVH elements 402, 430 generated by
a magnet, for example, the circular magnet 440 coupled to a shaft
442 and operable to rotate.
[0173] The angle calculation module 488 can generate an angle
signal 488a comprising information about the angle of the sensed
magnetic field. In some embodiments, the angle signal 488a can have
a digital count value related to the sensed angle of the magnetic
field.
[0174] The rotation speed module 420 can be coupled to receive the
angle signal 488a and can be operable to generate the speed signal
420a indicative of the speed of movement, e.g., the speed of
rotation, of a magnetic field as may be generated by the rotating
magnet 440.
[0175] The rotation direction module 422 can be coupled to receive
the angle signal 488a and can be operable to generate the direction
signal 422a indicative of a direction of movement, e.g., a
direction of rotation, of a magnetic field as may be generated by
the rotating magnet 440.
[0176] An output format module 490 can receive one or more of the
angle signal 488a, the speed signal 420a, or the direction signal
422a, and can generate an output signal 490a having one or more of
angle information, speed information, or direction information.
[0177] In an alternate embodiment, the multiplication module 478
can be replaced by a summing module 494 or a differencing module
496 in accordance with the above described first or second
sequencing embodiments.
[0178] While the magnetic field sensors 400, 450, and 470 are shown
to include first and second CVH elements 402, 430, it should be
apparent that the magnetic field sensors can include more than two
CVH elements that are combined in similar ways to generate one
output signal.
[0179] In other embodiments, the first and second CVH elements 402,
430 can be replaced by separate magnetic field sensing elements
arranged, for example, in respective circles comparable to the
plurality of magnetic field sensing elements of FIG. 1A.
[0180] All references cited herein are hereby incorporated herein
by reference in their entirety.
[0181] 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 that other
embodiments incorporating these concepts, structures and techniques
may be used. Accordingly, it is submitted that the 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.
[0182] Elements of embodiments described herein may be combined to
form other embodiments not specifically set forth above. Various
elements, which are described in the context of a single
embodiment, may also be provided separately or in any suitable
subcombination. Other embodiments not specifically described herein
are also within the scope of the following claims.
* * * * *