Capacitive Accelerometer Interface Circuit for Gain and Range Trimming
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Solution Overview
Problem
Existing capacitive accelerometer interface circuits face challenges in making the feedback capacitor programmable for both fine grain size and range trimming simultaneously, due to the difficulty in managing parasitic capacitance and accommodating varying acceleration ranges.
Innovation Solution
The interface circuit employs multiple programmable capacitors and switches to divide the programmability burden, allowing for easier gain trimming with a grounded capacitor and coarse grain size acceleration range selection using floating capacitors, facilitating precise programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single feedback capacitor is used for both fine grain size and range trimming, then the circuit structure is simple, but it becomes difficult to manage parasitic capacitance and achieve precise programming for both purposes simultaneously
Solution Approach 1:
The patent divides the single feedback capacitor into multiple separate capacitors: a first feedback capacitor for fine grain size trimming and a second feedback capacitor for coarse range trimming. This segmentation allows each capacitor to be optimized for its specific function, managing parasitic capacitance effectively while achieving precise programming for both fine and coarse adjustments without the complexity of a single programmable capacitor.
2Adaptability or versatility
If a single feedback capacitor is made programmable for both fine grain size and range trimming, then versatility is improved, but device complexity and difficulty of implementation increase
Solution Approach 1:
The patent segments the feedback capacitance function into two separate capacitors with distinct purposes: one dedicated to fine grain size trimming and another to coarse range trimming. This eliminates the need for a single complex programmable capacitor, reducing implementation complexity while maintaining full adaptability for both fine and coarse adjustments through simpler, dedicated components.
Solution Approach 2:
The patent achieves universality by providing multiple feedback capacitors that collectively serve the dual functions of fine grain size trimming and coarse range trimming. Instead of making one capacitor multi-functional (which increases complexity), the system uses multiple capacitors where the combination provides the complete programmable feedback function needed for different acceleration ranges and precision requirements.
Data Source
AI summary
The present invention relates to an interface circuit for a capacitive accelerometer sensor for measuring an acceleration value sensed by the sensor. The interface circuit comprises a plurality of electrical switches and three programmable capacitors. Two of the programmable capacitors are arranged to implement gain trimming of the interface circuit, while one of the programmable capacitors is arranged to implement acceleration range selection.