Methods and apparatus for error detection in a magnetic field sensor

Patent metadata

Field	Value
Publication number	US-10156461-B2
Application number	US-201414529497-A
Country	US
Kind code	B2
Filing date	Oct 31, 2014
Priority date	Oct 31, 2014
Publication date	Dec 18, 2018
Grant date	Dec 18, 2018

Abstract

A magnetic field sensor for detecting motion of an object includes error detection circuiting and processing. Magnetic field sensing elements are configured to generate at least two magnetic field signals in response to a magnetic field associated with the object which signals are used by detectors to generate right and left channel signals with edges indicative of motion of the object. A direction calculation processor responsive to right and left channel signals generates a direction signal having a state indicative of a direction of motion of the object and an output signal generator generates an output signal having a pulse indicative of the direction of motion of the object in response to the direction signal. An error detection processor responsive to the output signal and to the direction signal is configured to detect an error in at least one of the direction signal and the output signal.

First claim

What is claimed is:

1. A magnetic field sensor for detecting motion of an object, comprising:
a plurality of magnetic field sensing elements configured to generate at least two magnetic field signals in response to a magnetic field associated with the object;
a first detector circuit responsive to at least one of the magnetic field signals and configured to generate a right channel signal having edges indicative of motion of the object;
a second detector circuit responsive to at least one of the magnetic field signals and configured to generate a left channel signal having edges indicative of motion of the object;
a direction calculation processor responsive to the right and left channel signals to generate a direction signal having a state indicative of a direction of motion of the object, wherein the direction signal is generated in response to a predetermined state of the left channel signal occurring at an edge of the right channel signal;
an output signal generator responsive to the direction signal to generate an output signal having a pulse indicative of the direction of motion of the object; and
an error detection processor responsive to the output signal and to the direction signal to detect an error in the direction signal based on an edge of the direction signal not occurring at an edge of the right channel signal.

2. The magnetic field sensor of claim 1 , wherein the output signal generator comprises a pulse counter configured to generate the output signal pulse with a first predetermined duration to indicate a first direction of motion when the direction signal is in a first state and to generate the output signal pulse with a second predetermined duration to indicate a second direction of motion when the direction signal is in a second state.

3. The magnetic field sensor of claim 1 , wherein the error detection processor comprises an edge comparator responsive to the direction signal and to the right channel signal to provide a comparator output signal indicative of whether an edge of the direction signal coincides with an edge of the right channel signal.

4. The magnetic field sensor of claim 2 , wherein the error further comprises an error in the output signal comprising the output signal pulse not having one of the first predetermined duration or the second predetermined duration corresponding to the direction of motion of the object.

5. The magnetic field sensor of claim 4 , wherein the error detection processor comprises a pulse counter checker responsive to the direction signal and to the output signal and configured to generate a pulse count checker signal having a count value corresponding to the one of the first predetermined duration or the second predetermined duration corresponding to the direction of motion of the object.

6. The magnetic field sensor of claim 5 , wherein the error detection processor further comprises an error flag generator to generate an error flag signal in response to the output signal pulse having a duration that does not correspond to the count value of the pulse counter checker signal.

7. The magnetic field sensor of claim 1 , wherein the output signal generator further comprises a memory device.

8. The magnetic field sensor of claim 7 , wherein the memory device is configured to store one or more parameters comprising an output signal pulse duration, an error reporting type, and an output signal off-time.

9. The magnetic field sensor of claim 8 , wherein at least one of the stored parameters is user programmable.

10. The magnetic field sensor of claim 1 , wherein the object is comprised of a magnetic material and wherein the magnetic field is generated by the object.

11. The magnetic field sensor of claim 1 , wherein the object is comprised of a ferromagnetic material and wherein the magnetic field is affected by movement of the object.

12. The magnetic field sensor of claim 11 , further comprising a magnet and wherein the magnetic field is generated by the magnet.

13. The magnetic field sensor of claim 1 , wherein the plurality of magnetic field sensing elements are Hall effect elements.

14. The magnetic field sensor of claim 1 , wherein the plurality of magnetic field sensing elements are magnetoresistance elements.

15. The magnetic field sensor of claim 14 , wherein each of the magnetoresistance elements is one of: an anisotropic magnetoresistance (AMR) element, a giant magnetoresistance (GMR) element, a tunneling magnetoresistance (TMR) element, a magnetic tunnel junction (MTJ) element, or a spin valve element.

16. The magnetic field sensor of claim 1 , wherein the error further comprises an error in the output signal, wherein the output signal produces an error indicating pulse with a predetermined pulse width after a predetermined time period, and at least one of the predetermined pulse width and the predetermined time period is indicative of an error with the output signal.

17. A method for detecting an error in a magnetic field sensor for detecting motion of an object, comprising:
receiving at least two magnetic field signals generated in response to a magnetic field associated with the object;
generating a right channel signal having edges indicative of motion of the object in response to at least one of the magnetic field signals;
generating a left channel signal having edges indicative of motion of the object in response to at least one of the magnetic field signals;
generating a direction signal having a state corresponding to a first or second direction of motion of the object in response to the right and left channel signals;
generating an output signal having a pulse with a first preset pulse duration corresponding to a first direction of motion of the object when the direction signal is in a first state, and with a second preset pulse duration different than the first preset pulse duration and corresponding to a second direction of motion of the object when the direction signal is in a second state; and
detecting an error in the output signal, wherein the error comprises the output signal having a pulse duration other than the first preset pulse duration and other than the second preset pulse duration, by determining if the output signal pulse does not have one of the first and second preset pulse durations.

18. The method of claim 17 , wherein detecting the error further comprises detecting the error in the direction signal if an edge of the direction signal does not coincide with an edge of the right channel signal.

19. A magnetic field sensor for detecting motion of an object, comprising:
a plurality of magnetic field sensing elements configured to generate at least two magnetic field signals in response to a magnetic field associated with the object;
means for generating a right channel signal having edges indicative of motion of the object in response to at least one of the magnetic field signals;
means for generating a left channel signal having edges indicative of motion of the object in response to at least one of the magnetic field signals;
means for generating a direction signal having a state indicative of a first or second direction of motion of the object in response to the right and left channel signals, wherein the direction signal is generated in response to a predetermined state of the left channel signal occurring at an edge of the right channel signal;
means for generating an output signal having a pulse with a first preset duration to indicate a first direction of motion of the object when the direction signal is in a first state, and with a sec

Assignees

• Allegro Microsystems Llc

Inventors

• Snyder Steven E
• Mcconnell Craig
• Wells Peter G

Classifications

• G01P3/487 Primary

  delivered by rotating magnets · CPC title

• G01R33/098

  comprising tunnel junctions, e.g. tunnel magnetoresistance sensors · CPC title

• G01R33/096

  anisotropic magnetoresistance sensors · CPC title

• G01P21/02

  of speedometers · CPC title

• G01D18/00 Primary

  Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00 · CPC title