MEMS Accelerometer Self-Test Using Switch Network Decoupling
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Solution Overview
Problem
Existing MEMS capacitive accelerometers require additional capacitors and electrical contacts for testing, which complicates their design and increases component count, whereas the sensing capacitive elements themselves can be utilized for testing to simplify the design.
Innovation Solution
A method involving a switch network circuit in an integrated circuit (IC) that electrically decouples and couples capacitive elements of MEMS sensors to measure capacitance changes induced by an electrical signal, allowing for self-testing without additional test capacitors, using a capacitance measurement circuit and differential input ADC circuits to quantify capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional capacitors and electrical contacts are added for testing, then testing capability is improved, but device complexity increases
Solution Approach 1:
The sensing capacitive elements are designed to serve dual purposes: normal sensing operation and self-testing. The same capacitive elements that detect acceleration are also used as test objects, eliminating the need for separate test capacitors and reducing device complexity while maintaining testing capability
Solution Approach 2:
The MEMS sensor performs self-testing by using its own sensing capacitive elements as test objects. The system tests itself without requiring external test components, thereby simplifying the overall design and reducing the number of electrical contacts needed
2Reliability
If additional capacitors and electrical contacts are added for testing, then testing capability is improved, but number of components increases
Solution Approach 1:
The sensing capacitive elements perform both sensing and testing functions, eliminating the need for separate test capacitors. This reduces the total component count while maintaining full testing capability through the existing sensing elements
Solution Approach 2:
The system uses its own sensing capacitive elements for self-testing, eliminating the need for additional test components. This self-service approach reduces the quantity of components required while ensuring comprehensive testing capability
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 approach simplifies the design of MEMS sensors by eliminating dedicated testing components, reducing the number of circuit contacts, and enabling effective self-testing of capacitive accelerometers by utilizing the sensing capacitive elements for testing purposes.
Implementation Method 1
Capacitive accelerometers undergo a change in capacitance in response to acceleration. The capacitance measurement circuit is configured to measure capacitance of the second capacitive element during application of a first electrical signal to the decoupled first capacitive element.
Data Source
AI summary
An apparatus comprises a micro-electromechanical system (MEMS) sensor including a first capacitive element and a second capacitive element and an integrated circuit (IC). The IC includes a switch network circuit and a capacitance measurement circuit. The switch network circuit is configured to electrically decouple the first capacitive element of the MEMS sensor from a first input of the IC and electrically couple the second capacitive element to a second input of the IC. The capacitance measurement circuit can be configured to measure capacitance of the second capacitive element of the MEMS sensor during application of a first electrical signal to the decoupled first capacitive element.