Resettable Bipolar TMR Switch Sensor With Preset Initial State
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Solution Overview
Problem
Existing magnetic switch sensors face challenges in achieving low power consumption, high operating frequency, and precise positioning, which affects their accuracy and efficiency in various applications, particularly in consumer electronics and industrial settings.
Innovation Solution
A resettable bipolar switch sensor is developed, comprising a substrate with magnetoresistive sensing arms, a reset coil, and an ASIC switch circuit, utilizing TMR sensing units with a specific layered structure and laser programming for precise magnetization control, allowing for low power consumption and high-frequency operation with a presettable initial state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall sensors or AMR sensors are used to achieve magnetic field sensing, then the sensing function is provided, but the power consumption increases to microampere or milliampere level and operating frequency is limited to tens of Hertz or kilohertz
Solution Approach 1:
The patent changes the fundamental sensing mechanism from Hall effect or AMR to TMR (tunnel magnetoresistance) effect, which fundamentally alters the electrical parameters including resistance characteristics and current-voltage relationship. This parameter change enables microampere-level power consumption while maintaining high-frequency operation capability, directly resolving the contradiction between sensing capability and power consumption
Solution Approach 2:
The patent employs a composite magnetic multilayer structure including TMR sensing units with specific layer configurations (free layer, reference layer, intermediate layer) and integrates them with reset coils and bridge circuits. This composite structure combines multiple functional materials to achieve low power consumption, high frequency response, and precise magnetic field sensing simultaneously
2Measurement precision
If Hall sensors or AMR sensors are used, then magnetic field detection is achieved, but operating frequency is limited to tens of Hertz or kilohertz range
Solution Approach 1:
The patent changes the sensing mechanism to TMR effect with different temporal response characteristics, altering the frequency response parameter. The TMR-based sensor architecture enables operation in kilohertz to megahertz range, fundamentally improving the speed parameter while maintaining detection precision
Solution Approach 2:
The patent introduces dynamic reset capability through reset coils that can actively control the magnetization state of the free layer. This dynamic control allows the sensor to rapidly transition between states, enabling high-frequency operation by preventing saturation and maintaining responsiveness to changing magnetic fields
3Measurement precision
If a linear TMR magnetoresistive sensor with comparator is used to achieve rectangular output, then digital output is obtained, but the initial state consistency cannot be ensured without reset mechanism
Solution Approach 1:
The patent implements preliminary action by providing a reset mechanism that initializes the sensor state before each measurement cycle. The reset coil applies a magnetic field to set the free layer magnetization to a known state, ensuring consistent initial conditions for subsequent measurements and eliminating uncertainty about the sensor's starting state
Solution Approach 2:
The patent employs feedback through the reset control circuit that monitors the sensor output and automatically applies reset pulses when needed. This feedback mechanism ensures the sensor returns to a known reference state, maintaining reliability and consistency of the digital output across multiple operation cycles
4Measurement precision
If push-pull bridge structure with flipped chips is used, then the bipolar sensing is achieved, but positioning precision and manufacturing complexity increase
Solution Approach 1:
The patent merges multiple sensing functions into a single integrated chip structure rather than using separate flipped chips. The TMR sensing units are fabricated in an integrated bridge configuration on one substrate, eliminating the need for precise positioning of multiple chips and simplifying manufacturing while maintaining bipolar sensing capability
Solution Approach 2:
The patent creates a universal sensor chip that can detect magnetic fields in both positive and negative directions through the bridge configuration of TMR units. This multi-functional design achieves bipolar sensing without requiring separate chips for different directions, reducing manufacturing complexity and improving consistency
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 achieves low power consumption, small size, and precise control over the switch sensor's initial state, enhancing its accuracy and efficiency in high-frequency applications while overcoming the limitations of previous technologies.
Implementation Method 1
Sensors utilizing a tunnel magnetoresistive TMR element as a sensing element have the low power consumption, can work at an operating frequency in kilohertzes or even megahertzes
Implementation Method 2
a reset coil can be used to generate a reset magnetic field Hr, which acts on the N or S direction
Data Source
AI summary
A resettable bipolar switch sensor is disclosed which comprises a bipolar magnetic hysteresis switch sensor, a reset coil, an ASIC switch circuit and a power reset circuit. The bipolar magnetic hysteresis switch sensor comprises a substrate and a magnetoresistive sensing arm located on the substrate. The magnetoresistive sensing arm is of a two-port structure composed of one or more magnetoresistive sensing unit strings arranged in series, parallel, or series-parallel. The magnetization direction of a free layer of a TMR magnetoresistive sensing unit is determined by an anisotropy field Hk, and together with the magnetization direction of a reference layer and the applied magnetic field, it can orient in an N or S direction. The reset coil is located between the substrate along with the magnetoresistive sensing unit, or it is located on a lead frame below the substrate. The direction of the reset magnetic field is either N or S. The ASIC switch circuit comprises a biasing circuit module, a reading circuit module, and an output circuit module. The power reset circuit is connected to the reset coil. This device has the advantages of low power consumption and small size in addition to the capability to set initial state of the switch sensor.