Dual-Path Analog to Digital Converter

• US 20160139229A1
• Filed: 11/14/2014
• Published: 05/19/2016
• Est. Priority Date: 11/14/2014
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Choe, Soo-Chang, Petrie, Craig S.
• Granted Patent: US 9,804,249 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01D 5/142 using Hall-effect devices measuring magnetic variables using Hall-effect or other galvanomagnetic devices G01R33/06
• CPC Class Codes: G01R 33/0017 Means for compensating offset magnetic fields or the magnetic flux to be measured; Means for generating calibration magnetic fields
• CPC Class Codes: G01R 33/0035 Calibration of single magnetic sensors, e.g. integrated calibration
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: G01R 33/09 Magnetoresistive devices
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence
• CPC Class Codes: H03M 1/34 Analogue value compared with reference values H03M1/48 takes precedence
• CPC Class Codes: H03M 3/458 Analogue/digital converters using delta-sigma modulation as an intermediate step

Abstract

Methods and apparatus for processing a signal comprise at least one circuit configured to generate a measured signal during a measured time period and a reference signal during a reference time period. Also included is at least one dual- or multi-path analog-to-digital converter comprising at least a first processing circuit configured to process the measured signal, at least a second processing circuit configured to process the reference signal, and a third processing circuit configured to process both the measured signal and the reference signal.

Claims

1. An apparatus comprising:

at least one circuit configured to generate a measured signal during a measured time period and a reference signal during a reference time period; and

at least one multi-path analog-to-digital converter comprising at least a first processing circuit configured to process the measured signal and a second processing circuit configured to process the reference signal and a third processing circuit configured to process both the measured signal and the reference signal.

2. The apparatus of claim 1 wherein the measured time period and the reference time period are alternating time periods.

3. The apparatus of claim 1 further comprising a control circuit configured to enable the first processing circuit during the measured time period and to enable the second processing circuit during the reference time period.

4. The apparatus of claim 1 wherein the analog-to-digital converter comprises at least one integrator circuit.

5. The apparatus of claim 4 wherein the first processing circuit comprises a first capacitor and the second processing circuit comprises a second capacitor.

6. The apparatus of claim 1 wherein the at least one circuit configured to generate the measured signal and the reference signal comprises at least one magnetic field sensing element.

7. The apparatus of claim 6 wherein the at least one magnetic field sensing element comprises a Hall effect element, a magnetoresistive element, or both.

8. The apparatus of claim 1 further comprising a fault circuit configured to determine whether an output signal of the apparatus, generated by the apparatus in response to the reference signal, indicates a fault in the apparatus.

9. The apparatus of claim 1 further comprising a calibration circuit configured to combine the processed measured signal with the processed reference signal to generate a calibrated magnetic field signal.

10. The apparatus of claim 8 wherein the fault circuit determines whether the output signal indicates a fault by comparing the output signal to an expected value.

11. The apparatus of claim 1 wherein the analog-to-digital converter is a sigma-delta analog-to-digital converter.

12. The apparatus of claim 1 further comprising a built in self-test circuit configured to detect an error in the apparatus.

13. A analog-to-digital converter comprising:

input configured to receive a measured signal and a reference signal;

at least one shared circuit coupled to receive the signal and reference signal from the input, and configured to process both the signal and the reference signal through a single signal path of the one shared circuit;

a measured signal circuit configured to process the measured signal; and

a reference signal circuit configured to process the reference signal.

14. The analog-to-digital converter of claim 13 further wherein the input is configured to receive the measured signal during a measured time period and to receive the reference magnetic field signal during a reference time period.

15. The analog-to-digital converter of claim 14 wherein the measured time period and the reference time period are alternating time periods.

16. The analog-to-digital converter of claim 14 further comprising a control circuit configured to enable the measured signal circuit during the measured time period and to enable the reference signal circuit during the reference time period.

17. The analog-to-digital converter of claim 14 wherein the control circuit is further configured to swap the measured signal circuit and the reference signal circuit so that the measured signal circuit is enabled during the reference time period and the reference signal circuit is enabled during the measured time period.

18. The analog-to-digital converter of claim 13 wherein the analog-to-digital converter is a sigma-delta analog-to-digital converter.

19. A magnetic field sensor comprising:

at least one magnetic field sensing element configured to generate a measured magnetic field signal responsive to an external magnetic field and to generate a reference magnetic field signal responsive to a reference magnetic field; and

a signal path for processing the measured magnetic field signal during a measured time period and processing the reference magnetic field during a reference time period, the signal path comprising a dual-path analog-to-digital converter.

20. The magnetic field sensor of claim 19 further comprising a comparison circuit to determine whether an output signal of the signal path during the measured time period indicates a fault condition by comparing the output signal to an expected value.

21. The magnetic field sensor of claim 19 further comprising a reference coil proximate to the at least one magnetic field sensing element, wherein the reference coil is configured to carry a reference current to generate the reference magnetic field.

22. The magnetic field sensor of claim 19 wherein the dual-path analog-to-digital converter includes a first path for processing the measured magnetic field signal and a second path for processing the reference magnetic field signal.

23. The magnetic field sensor of claim 22 further comprising a control circuit configured to enable the first path during the measured time period and to enable the second path during the reference time period.

24. The magnetic field sensor of claim 23 wherein in the analog-to-digital converter comprises an integrator circuit with one or more first capacitors as part of the first path, and one or more second capacitors as part of the second path.

25. The magnetic field sensor of claim 24 wherein the control circuit is configured to:

couple the one or more first capacitors to the signal path during the measured time period;

decouple the one or more first capacitors from the signal path during the reference time period;

couple the one or more second capacitors to the signal path during the reference time period; and

decouple the one or more second capacitors from the signal path during the measured time period.

26. The magnetic field sensor of claim 24 wherein the control circuit is configured to swap the one or more first and second capacitors to enable to first capacitors to process the reference magnetic field signal and enable the second capacitors to process to measured magnetic field signal.

27. The magnetic field sensor of claim 19 further comprising a built in self-test circuit configured to detect an error in magnetic field sensor.

28. A method of testing a magnetic field sensor comprising:

generating a measured signal;

generating a reference signal;

processing the measured signal with a signal path of the magnetic field sensor during a measured time period, wherein the signal path includes a dual-path analog-to-digital converter (“

ADC”

);

processing the reference signal with the signal path of the magnetic field sensor during a reference time period; and

enabling a first path of a dual-path ADC during the measured time period and enabling a second path of the dual-path ADC during the reference time period.

29. The method of claim 28 wherein enabling includes:

coupling a first capacitor of the ADC to the signal path during the measured time period;

decoupling the first capacitor of the ADC from the signal path during the reference time period;

coupling a second capacitor of the ADC to the signal path during the reference time period; and

decoupling the second capacitor of the ADC from the signal path during the measured time period.

30. The method of claim 29 further comprising swapping the first capacitor with the second capacitor so the first capacitor is coupled to the signal path during the reference time period and the second capacitor is coupled to the signal path during the measured time period.

31. The method of claim 28 further comprising measuring an output signal of the signal path responsive to the reference magnetic field signal to determine if a fault occurred.

32. The method of claim 31 wherein measuring includes comparing the output signal to an expected value.

33. The method of claim 28 wherein generating the measured magnetic field signal comprises sensing an external magnetic field with a magnetic field sensing element.

34. The method of claim 28 wherein generating the reference magnetic field signal comprises sensing a reference magnetic field with a magnetic field sensing element.

35. The method of claim 34 wherein sensing the reference magnetic field comprises sensing a magnetic field generated by a coil proximate to the magnetic field sensing element.