Integrated GMR Magnetic Sensor with On-Die Coil
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Solution Overview
Problem
Existing magnetic field sensors lack sensitivity and efficiency in detecting changes in magnetic fields generated by moving ferromagnetic targets, particularly in applications requiring precise position, speed, and direction sensing.
Innovation Solution
Integration of a giant magnetoresistance (GMR) element with a coil on a die, where the coil generates a magnetic field that is detected by the GMR element, enhancing sensitivity and allowing for reduced coil size and current requirements, with optional inclusion of Hall elements for complementary sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional magnetic field sensor is used, then the device structure is simple, but the sensitivity to magnetic field changes is insufficient
Solution Approach 1:
The patent combines the coil and GMR sensing element into a single integrated sensor structure on one die. The coil is formed on the die surface and the GMR element is positioned beneath or adjacent to the coil, creating a compact integrated device that achieves high sensitivity without requiring separate discrete components.
Solution Approach 2:
The integrated sensor structure serves multiple functions: the coil generates the magnetic field and also acts as part of the sensing structure, while the GMR element provides the magnetic field detection. This multi-functional design achieves high measurement precision without proportionally increasing device complexity.
2Power
If a larger coil is used to generate a stronger magnetic field, then the magnetic field strength increases, but the device size increases
Solution Approach 1:
The patent uses GMR elements which have high sensitivity to magnetic field changes, allowing the use of smaller coils with lower current requirements. The GMR effect enables detection of very small magnetic field variations, so the coil can be miniaturized while maintaining sufficient magnetic field strength for accurate sensing.
Solution Approach 2:
The magnetic field generation is localized to the immediate area above the GMR element. The coil is positioned directly over the sensing element, concentrating the magnetic field where it is needed rather than generating a broad field across a large area. This localized approach reduces the required coil size while maintaining effective magnetic field strength at the sensing point.
3Power
If higher current is used to excite the coil, then the magnetic field strength increases, but the power consumption increases
Solution Approach 1:
The high sensitivity of GMR elements to magnetic field changes allows the coil to be excited with lower current while still producing sufficient magnetic field variation for accurate detection. The GMR element can detect very small changes in magnetic field, so the excitation current can be reduced without compromising measurement precision, thereby reducing power consumption.
4Measurement precision
If discrete components are used for coil and sensing element, then the device is easier to manufacture, but the overall sensor performance is reduced
Solution Approach 1:
The coil and GMR sensing element are integrated onto a single die using compatible fabrication processes. The coil is formed using standard semiconductor metallization layers, and the GMR element is positioned and connected in the same integrated structure. This integration maintains manufacturing simplicity while achieving superior sensor performance through optimized spatial relationships between components.
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
The solution provides improved sensitivity to magnetic field changes, enabling accurate detection of ferromagnetic target movement, position, speed, and direction with reduced power consumption and component size, suitable for various applications including seat position and buckle presence sensors.
Implementation Method 1
a coil proximate the die to generate a magnetic field
Implementation Method 2
a giant magnetoresistance (GMR) element, which has more sensitivity to magnetic field changes than a comparable Hall element
Implementation Method 3
Hall effect elements generate an output voltage proportional to a magnetic field
Data Source
AI summary
Methods and apparatus for a magnetic sensor having a die and sensor circuitry formed in a device layer of the die with a coil integrated with the die to generate a magnetic field. A magnetoresistive magnetic field sensing element on the die detects changes in the magnetic field generated by the coil as a result of the presence of a ferromagnetic target. The sensor circuitry may process the changes in the magnetic field generated by the coil.