System and method for sensor diagnostics during functional operation

A system comprising:

• a magnetic field sense element configured to detect an external magnetic field, wherein the system selectively functions in-situ in either of the operational mode and a standby mode, the external magnetic field is available for detection by the magnetic sense element in the operational mode, and the external magnetic field is not available for detection by the magnetic sense element in the standby mode;
• a magnetic field source proximate the magnetic field sense element and configured to provide a reference magnetic field that is detectable by the magnetic sense element, wherein the magnetic field sense element is configured to produce a composite signal having a reference signal portion and a measurement signal portion, the reference signal portion being indicative of the reference magnetic field and the measurement signal portion being indicative of the external magnetic field;
• a power supply coupled with the magnetic field source and configured to provide a supply current through the magnetic field source for continuously generating the reference magnetic field while the system is in the operational and standby modes;
• and
• a processing circuit coupled with the magnetic sense element, the processing circuit being configured to process the measurement signal portion of the composite signal to produce a measurement output signal indicative of the external magnetic field when the system is in the operational mode, and the processing circuit being further configured to process the reference signal portion of the composite signal to produce a reference output signal indicative of the reference magnetic field when the system is in the standby mode, wherein the magnetic sense element, the magnetic field source, the power supply, and the processing circuit are implemented within a speed sensor system, and the standby mode is a standstill mode of the speed sensor system in which the speed sensor system detects that an object is immobile in response to an absence of the external magnetic field.

In a system capable of functioning in-situ in either of an operational mode and a standby mode, the system including a magnetic sense element, a method comprising:

• continuously energizing a magnetic field source proximate the magnetic sense element when the system is in both of the operational mode and the standby mode, the magnetic field source providing a reference magnetic field that is detectable by the magnetic sense element;
• detecting an external magnetic field and the reference magnetic field at the magnetic sense element;
• producing a composite signal having a reference signal portion and a measurement signal portion, the reference signal portion being indicative of the reference magnetic field and the measurement signal portion being indicative of the external magnetic field;
• processing the composite signal, at a processing circuit, to produce a measurement output signal indicative of the external magnetic field;
• converting the composite signal to a digitized composite signal;
• detecting a qualification reference signal portion at a qualification circuit coupled with the processing circuit at multiple test points by filtering the digitized composite signal at the qualification circuit to detect a digitized qualification reference signal portion of the reference signal portion in the digitized composite signal;
• and
• determining, at the qualification circuit, an operability of at least a portion of the system from the digitized qualification reference signal portion detectable at each of the multiple test points;
• and
• producing a first error flag when the digitized qualification reference signal portion is outside of a first expected signal range, the first error flag being indicative of a first fault condition of the system.

A speed sensor system comprising:

• magnetic field sense elements configured to detect an external magnetic field, wherein the speed sensor system selectively functions in-situ in either of an operational mode and a standby mode, the external magnetic field is available for detection by the magnetic sense elements in the operational mode, and the external magnetic field is not available for detection by the magnetic sense element in the standby mode;
• a magnetic field source proximate the magnetic field sense elements and configured to provide a reference magnetic field that is detectable by the magnetic sense elements, wherein the magnetic field sense elements are configured to produce a composite signal having a reference signal portion and a measurement signal portion, the reference signal portion being indicative of the reference magnetic field and the measurement signal portion being indicative of the external magnetic field;
• a power supply coupled with the magnetic field source and configured to provide a supply current through the magnetic field source for continuously generating the reference magnetic field while the speed sensor system is in the operational and standby modes;
• a processing circuit coupled with the magnetic sense elements, the processing circuit being configured to process the composite signal to produce a measurement output signal indicative of the external magnetic field, wherein the processing circuit comprises an analog-to-digital converter (ADC) system configured to receive the composite signal and convert the composite signal to a digitized composite signal;
• and
• a qualification circuit coupled with the processing circuit at multiple test points, the qualification circuit being configured to detect the reference signal portion at the multiple test points and determine an operability of at least a portion of the system from the reference signal portion detectable at each of the multiple test points, wherein the multiple test points include a first test point, the first test point including a first interconnect between the ADC system and the qualification circuit, wherein the qualification circuit is configured to detect a digitized qualification reference signal portion of the reference signal portion in the digitized composite signal and produce a first error flag when the digitized qualification reference signal portion is outside of a first expected signal range.