Magnetic Sensor Circuit with Dual-Range Signal Combination
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Solution Overview
Problem
Current magnetic field sensors have limited magnetic sensitivity and bandwidth due to eddy currents and noise issues, resulting in a restricted frequency range and low signal-to-noise ratio, especially at high frequencies.
Innovation Solution
A system comprising an on-chip magnetic sensor for low-frequency fields and an off-chip magnetic sensor for high-frequency fields, with a shared cross-over frequency, where signals from both sensors are combined using a sensor circuit to produce a flat response from DC to several MHz, avoiding limitations imposed by the leadframe and enhancing design flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Hall plate is used as a magnetic field sensor, then moderate magnetic sensitivity is achieved, but bandwidth is limited to 30 kHz due to eddy currents in the leadframe
Solution Approach 1:
The patent divides the magnetic field sensing function across two separate sensors: a Hall plate for low-frequency fields and an on-chip coil for high-frequency fields. This segmentation allows each sensor to operate in its optimal frequency range, with the Hall plate handling DC to low frequencies and the coil handling high frequencies, thereby achieving both moderate sensitivity and extended bandwidth without the eddy current limitations of a single sensor.
2Speed
If an on-chip coil is used as a magnetic field sensor, then large bandwidth is achieved, but magnetic sensitivity is limited due to small effective area and limited number of turns
Solution Approach 1:
The patent merges the output signals from two different magnetic sensors (Hall plate and on-chip coil) through a sensor circuit that combines their respective sensor signals. This combination allows the system to achieve the large bandwidth of the coil while compensating for its limited sensitivity by incorporating the Hall plate's signal, which has moderate sensitivity but lower bandwidth.
3Device complexity
If magnetic field sensor elements with high resistance are used, then device simplicity is maintained, but noise increases at high frequencies restricting operating frequency
Solution Approach 1:
The patent introduces an intermediary on-chip coil sensor that operates in the high-frequency range where resistive sensors generate excessive noise. The coil acts as a mediator for high-frequency magnetic field detection, while the Hall plate handles lower frequencies, and their signals are combined to produce a flat frequency response without the high-frequency noise limitations of purely resistive sensors.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration significantly increases the frequency bandwidth and sensitivity, allowing for effective detection of magnetic fields across a wide range without the noise and offset errors typical in single-sensor systems, while maintaining low residual offset and noise.
Implementation Method 1
magnetic field sensor elements sensitive to magnetic fields, and output an electric signal (e.g., voltage signal or current signal) corresponding to the measured magnetic field
Implementation Method 2
An on-chip coil disposed on a surface of a semiconductor chip may also be used as a magnetic field sensor element
Implementation Method 3
a sensor circuit is electrically coupled to the first magnetic sensor and to the second magnetic sensor, the sensor circuit is configured to receive the first sensor signal and the second sensor signal, combine the first sensor signal and the second sensor signal, and output a combined sensor signal
Data Source
AI summary
Sensor devices, systems and methods are provided, including a first magnetic sensor configured to measure a first magnetic field in a first frequency range and output a first sensor signal based on the measured first magnetic field, a second magnetic sensor configured to measure a second magnetic field in a second frequency range and output a second sensor signal based on the measured second magnetic field, and a sensor circuit configured to receive the first and the second sensor signals, combine the first and the second sensor signals, and output a combined sensor signal. The first magnetic sensor and the second magnetic sensor are configured to share a cross-over frequency.