CIRCULAR VERTICAL HALL (CVH) SENSING ELEMENT WITH SIGNAL PROCESSING AND ARCTANGENT FUNCTION

• US 20170219665A1
• Filed: 02/01/2016
• Published: 08/03/2017
• Est. Priority Date: 02/01/2016
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Alpago, Octavio H., Alves, Ezequiel, Romero, Hernn D.
• Granted Patent: US 10,481,220 B2
• Time in Patent Office: Days
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/2448 Correction of gain, threshold, offset or phase control
• CPC Class Codes: G01R 33/0029 Treating the measured signals, e.g. removing offset or noise
• CPC Class Codes: G01R 33/077 Vertical Hall-effect devices

Abstract

A magnetic field sensor includes a circular vertical Hall (CVH) sensing element to produce a signal representing an external magnetic field as detected by the CVH sensing element, a sigma-delta analog-to-digital converter to generate a converted signal, modulators to produce quadrature modulated signals from the converted signal, and a processor to produce an estimated angle of the external magnetic field using the quadrature modulated signals. An arctangent function may be used to calculate the estimated angle. A sliding window integration scheme may be used over one or more CVH cycles.

Claims

1. A magnetic field sensor, comprising:

a circular vertical Hall (CVH) sensing element to produce an analog signal representing an external magnetic field;

an analog-to-digital converter coupled to receive the analog signal and produce a digital signal;

an quadrature modulator circuit coupled to the digital signal and operable to generate a plurality of quadrature modulated signals; and

a processor stage coupled to receive signals representative of the plurality of quadrature modulated signals and operable to perform an arctangent calculation to compute an estimated angle of the external magnetic field.

2. The magnetic field sensor of claim 1 wherein the processor stage comprises a circuit to perform a CORDIC algorithm.

3. The magnetic field sensor of claim 2 wherein the circuit to perform the CORDIC algorithm is a processor configured to execute instructions that cause the processor to perform the CORDIC algorithm.

4. The magnetic field sensor of claim 3 wherein the instructions are software instructions, firmware instructions, micro-code instructions, or a combination thereof.

5. The magnetic field sensor of claim 1 wherein the arctangent calculation produces an estimated angle has an accuracy greater than a predetermined angle between one or more vertical Hall element contacts of the CVH sensing element.

6. The magnetic field sensor of claim 1 wherein the analog-to-digital converter is a sigma-delta analog-to-digital converter and the digital signal is a pulse stream.

7. The magnetic field sensor of claim 6 wherein the sigma-delta analog-to-digital converter comprises a noise shaping transform that shifts quantization noise to higher frequencies.

8. The magnetic field sensor of claim 1 wherein the processor stage is further configured to perform a sliding window integration using the signals representative of the plurality of quadrature modulated signals.

9. The magnetic field sensor of claim 1 wherein the processor stage is configured to perform the arctangent calculation to compute the estimated angle at a frequency greater than that of a CVH cycle.

10. The magnetic field sensor of claim 1 wherein the quadrature modulator circuit is configured to produce a first modulated signal that is modulated with a cosine function and a second modulated signal that is modulated with a sine function.

11. The magnetic field sensor of claim 10 wherein the processor stage is configured to calculate a quotient of the first modulated signal divided by the second modulated signal.

12. The magnetic field sensor of claim 11 wherein the processor stage is configured to perform the arctangent calculation using the quotient.

24. The magnetic field sensor of claim 11 wherein performing the arctangent calculation comprises performing the arctangent calculation using the quotient.

13. A method comprising:

detecting a magnetic field by a circular vertical Hall (CVH) sensing element;

producing, by the CVH sensing element, an analog signal representing the external magnetic field;

converting the analog signal to a digital signal;

generating a plurality of quadrature modulated signals; and

performing an arctangent calculation to compute an estimated angle of the external magnetic field.

14. The method of claim 13 wherein performing the arctangent calculation comprises performing a CORDIC algorithm.

15. The method of claim 14 wherein the CORDIC algorithm is performed by a processor configured to execute instructions that cause the processor to perform the CORDIC algorithm.

16. The method of claim 15 wherein the instructions are software instructions, firmware instructions, micro-code instructions, or a combination thereof.

17. The method of claim 13 wherein the performing the arctangent calculation comprises producing an estimated angle that has an accuracy greater than a predetermined angle between one or more vertical Hall element contacts of the CVH sensing element.

18. The method of claim 13 wherein converting the analog signal comprises generating a sigma-delta encoded bit stream representing the analog signal.

19. The method of claim 18 wherein converting the analog signal comprises applying a noise shaping transform to the analog signal that shifts quantization noise to higher frequencies.

20. The method of claim 13 further comprising performing a sliding window integration using the plurality of quadrature modulated signals.

21. The method of claim 20 further comprising performing the arctangent calculation to compute the estimated angle at a frequency greater than that of a CVH cycle.

22. The method of claim 13 wherein generating the plurality of quadrature signals comprises modulating a first signal with a cosine function to produce a first modulated signal and modulating a second signal with a sine function to produce a second modulated signal.

23. The method of claim 22 further comprising calculating a quotient of the first modulated signal divided by the second modulated signal.