Magnetic Field Sensor Error Detection Circuitry
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Solution Overview
Problem
Magnetic field sensors in safety-critical applications like automobile control systems face challenges in detecting errors after installation, due to limited test opportunities and interference with normal operation, which can lead to undetected failures.
Innovation Solution
A magnetic field sensor with built-in error detection circuitry that includes a pulse counter and error detection processor to generate error flag signals when output signal pulses do not correspond to predetermined durations, allowing for error detection during operation rather than just during manufacturing or testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If built-in self-test circuitry is implemented in magnetic field sensors, then error detection capability is improved, but device complexity increases
Solution Approach 1:
The patent merges the error detection function with the existing output protocol circuitry by adding an error detection processor that shares the same signal paths and resources. The pulse counter is integrated into the output protocol circuit to generate both valid output pulses and error detection signals, eliminating the need for completely separate test circuitry.
Solution Approach 2:
The magnetic field sensor performs self-diagnosis by monitoring its own output signals. The error detection processor continuously analyzes the pulse widths generated by the pulse counter and compares them against expected values, allowing the sensor to autonomously detect errors in its direction signal generation without external testing equipment.
2Reliability
If error detection is performed during normal operation, then safety in safety-critical applications is improved, but interference with normal operation occurs
Solution Approach 1:
The error detection processor operates continuously during normal sensor operation, constantly monitoring the pulse widths of direction signals without interrupting the generation of these signals. The same signal paths are used for both normal operation and error detection, ensuring uninterrupted functional operation while maintaining continuous safety monitoring.
Solution Approach 2:
The system implements feedback by comparing the actual pulse widths generated by the pulse counter against predetermined valid pulse width values. When a discrepancy is detected, an error flag is generated to indicate potential failures, providing continuous safety feedback without disrupting normal sensor functionality.
Data Source
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AI summary
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.