Dual-Scale Triaxial Accelerometers With Unified MEMS Self-Test
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Solution Overview
Problem
Existing inertial MEMS devices with different sensitivity scales face challenges in performing a unified self-test due to the need for separate control units and procedures, leading to increased complexity, cost, and size.
Innovation Solution
An inertial MEMS device integrates a triaxial gyroscope and triaxial accelerometers with different sensitivity scales on a single die, allowing a unified self-test procedure using the same test signals, with high-G accelerometers capable of sensing at least 450 mG.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two separate movable sensing structures (low-G and high-G) are integrated into different dice, then both low acceleration and high acceleration sensing functions are achieved, but device dimensions increase and multiple dedicated control units are required
Solution Approach 1:
The patent merges both low-G and high-G movable sensing structures into a single integrated die, eliminating the need for separate dice and reducing overall device volume. The structures share common infrastructure including support beams, anchoring structures, and control circuitry while maintaining distinct sensing capabilities.
Solution Approach 2:
A single control unit is designed to universally control both low-G and high-G accelerometers through a unified self-test procedure. The control unit can dynamically adjust test signal parameters (amplitude, frequency) to accommodate the different sensitivity ranges of both sensor types, eliminating the need for multiple dedicated control units.
2Reliability
If two separate control units are used for low-G and high-G accelerometers, then dedicated self-test procedures can be performed, but device complexity and cost increase
Solution Approach 1:
A single control unit is designed with multi-functional capabilities to perform self-tests on both low-G and high-G accelerometers. The control unit includes adjustable signal generation circuitry that can modify test signal amplitude and frequency to match the specific requirements of each sensor type, and a unified processing algorithm that handles responses from both sensors.
Solution Approach 2:
The self-test procedure utilizes parameter changes in the test signal (amplitude, frequency, duration) to accommodate the different sensitivity characteristics of low-G and high-G accelerometers. The control unit dynamically adjusts these parameters based on which sensor is being tested, enabling a single control unit to effectively manage both sensor types without requiring separate dedicated control circuits.
3Device complexity
If a single control unit is used for both low-G and high-G accelerometers, then device complexity is reduced, but different self-test procedures are still required due to different sensitivity levels
Solution Approach 1:
The unified self-test procedure employs parameter changes in the test signal characteristics. For low-G accelerometers, the control unit applies lower amplitude test signals at frequencies optimized for their resonance characteristics. For high-G accelerometers, higher amplitude test signals are applied. The control unit automatically selects and adjusts these parameters based on the target sensor, presenting a unified interface to the user.
Solution Approach 2:
The self-test procedure is designed to be dynamic rather than static. The control unit adaptively adjusts test signal parameters in real-time based on which accelerometer type is being tested and its specific characteristics. This dynamic approach allows a single control unit to effectively manage the diverse requirements of both low-G and high-G sensors through one procedural interface.
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 enables efficient and cost-effective testing of both high and low sensitivity accelerometers using a single control unit, reducing device complexity and size while maintaining high sensitivity and accuracy.
Implementation Method 1
The accelerometers are of a capacitive type and include a fixed electrode and a movable electrode facing each other with a gap therebetween
Implementation Method 2
the control unit applies a known electrostatic force to the respective structure under test, providing a stimulus (for example voltage steps at a predetermined frequency) of suitable value
Data Source
AI summary
An inertial MEMS device has a plurality of inertial sensors integrated in a die of semiconductor material. The inertial sensors are mutually arranged side by side and include a triaxial gyroscope, a first triaxial accelerometer having a first full scale, and a second triaxial accelerometer having a second full scale greater than the first full scale. The first and the second triaxial accelerometers are of a capacitive type and configured to receive same self-test signals. The second triaxial accelerometer is configured to allow a self-test of accelerations of at least 450 mG, in particular of approximately 500 mG.