Magnetic field sensor with shared path amplifier and analog-to-digital-converter

• US 10,466,298 B2
• Filed: 09/20/2017
• Issued: 11/05/2019
• 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: Chaware, Virag V., Cook, Aaron, Petrie, Craig S.
• Primary Examiner(s): Allgood, Alesa
• Application Number:
  US15/710,136
• Publication Number:
  US 20180011140A1
• Time in Patent Office: 776 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: G01D 5/2449 using hard-stored calibration data
• CPC Class Codes: G01R 15/20 using galvano-magnetic devices, e.g. Hall-effect devices , i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
• CPC Class Codes: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844
• CPC Class Codes: G01R 31/2884 using dedicated test connectors, test elements or test circuits on the IC under test G01R31/2855 takes precedence
• CPC Class Codes: G01R 33/0035 Calibration of single magnetic sensors, e.g. integrated calibration
• CPC Class Codes: G01R 33/0041 using feed-back or modulation techniques
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: G01R 33/09 Magnetoresistive devices
• CPC Class Codes: G01R 35/00 Testing or calibrating of apparatus covered by the other groups of this subclass

Abstract

A magnetic field sensor comprises at least one magnetic field sensing element configured to generate a measured magnetic field signal responsive to an external magnetic field; a diagnostic circuit configured to generate a diagnostic signal, wherein the diagnostic signal is not dependent on a measured magnetic field; a signal path comprising an amplifier and an analog-to-digital converter for processing the measured magnetic field signal to generate a sensor output signal indicative of the external magnetic field during a measured time period and for processing the diagnostic signal during a diagnostic time period; and a switch coupled to receive the measured magnetic field signal and the diagnostic signal and direct the measured magnetic field signal to the signal path during the measured time period and direct the diagnostic signal to the signal path during the diagnostic time period.

Claims

1. 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;

a diagnostic circuit configured to generate a diagnostic signal, wherein the diagnostic signal is not dependent on a measured magnetic field;

a signal path comprising an amplifier and an analog-to-digital converter for processing the measured magnetic field signal to generate a sensor output signal indicative of the external magnetic field during a measured time period and for processing the diagnostic signal during a diagnostic time period, wherein the analog-to-digital converter is responsive to the measured magnetic field signal to generate a digital measure magnetic field signal and responsive to the diagnostic signal to generate a digital diagnostic signal, wherein the analog-to-digital converter comprises at least one integrator circuit having a first capacitor configured to process the measured magnetic field signal and a second capacitor configured to process the diagnostic signal;

a controller configured to selectively couple the first capacitor to the signal path during the measured time period and couple the second capacitor to the signal path during the diagnostic time period; and

a switch coupled to receive the measured magnetic field signal and the diagnostic signal and direct the measured magnetic field signal to the signal path during the measured time period and direct the diagnostic signal to the signal path during the diagnostic time period.

2. The magnetic field sensor of claim 1 further comprising a coil to generate the external magnetic field.

3. The magnetic field sensor of claim 1 wherein the diagnostic circuit is configured to generate the diagnostic signal during one of:

the diagnostic time period, the measured time period, or both the diagnostic and measured time periods.

4. The magnetic field signal of claim 1 further comprising an output signal generator responsive to the measured magnetic field signal and to the diagnostic signal to generate the sensor output signal.

5. The magnetic field sensor of claim 1 wherein the at least one magnetic field sensing element comprises:

a Hall effect element, a magnetoresistance element, or both.

6. 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;

a diagnostic circuit configured to generate a diagnostic signal;

a signal path comprising a shared portion for processing the measured magnetic field signal to generate a sensor output signal indicative of the external magnetic field during a measured time period and for processing the diagnostic signal to determine whether a fault is present during a diagnostic time period, and a dedicated portion for processing the measured magnetic field signal during the measured time period;

an analog-to-digital converter comprising at least one integrator and wherein the dedicated signal path portion comprises a first capacitor dedicated to processing the measured magnetic field signal and a second capacitor dedicated to processing the diagnostic signal; and

a controller configured to enable the dedicated signal path portion to process the diagnostic signal and to selectively couple the first capacitor to the signal path during the measured time period and couple the second capacitor to the signal path during the diagnostic time period.

7. The magnetic field sensor of claim 6 wherein the diagnostic circuit is electrically coupled directly to the at least one magnetic field sensing element to direct the diagnostic signal to the at least one magnetic field sensing element.

8. The magnetic field sensor of claim 7 wherein the diagnostic signal is a power signal that drives the at least one magnetic field sensing element.

9. 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;

a diagnostic circuit configured to generate a diagnostic signal;

a multiplexor coupled to receive the measured magnetic field signal and the diagnostic signal as inputs, and provide either the magnetic field signal or the diagnostic signal as an output;

a signal processing path coupled to receive the output of the multiplexor and process the measured magnetic field signal to generate a sensor output signal indicative of the external magnetic field during a measured time period, and process the diagnostic signal to determine whether a fault is present during a non-overlapping diagnostic time period; and

a control circuit coupled to the multiplexor and configured to cause the multiplexor to provide the measured magnetic field signal as the output during the measured time period, and provide the diagnostic signal as the output during the diagnostic time period, wherein the control circuit is configured to selectively couple a first ADC signal path to the signal processing path during the measured time period and selectively couple a second ADC signal path to the signal processing path during the diagnostic time period.

10. The magnetic field sensor of claim 9 wherein the at least one magnetic field sensing element is selected from a Hall effect element, a magnetoresistance element, or both.

11. The magnetic field sensor of claim 9 further comprising an analog-to-digital converter (ADC) responsive to the measured magnetic field signal to generate a digital measured magnetic field signal and responsive to the diagnostic signal to generate a digital diagnostic signal.

12. The magnetic field sensor of claim 11 wherein the ADC comprises the first ADC signal path for processing the measured magnetic field signal and the second ADC signal path for processing the diagnostic signal.