MEMS Acoustic Transducer Interface Circuit With Ratiometric Biasing
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Solution Overview
Problem
Current interface electronic circuits for acoustic transducers face limitations in managing wide ranges of supply voltage while maintaining high performance in terms of Power-Supply Rejection Ratio (PSRR) and Acoustic Overload Point (AOP), often requiring a choice between optimization for low voltage or high AOP, leading to non-linear behavior and discontinuity issues.
Innovation Solution
A ratiometric design for the interface electronic circuit that automatically adjusts the operating point of the amplifier stage and common-mode voltage based on the supply voltage, using a reference-generator stage to generate variable reference voltages proportional to the supply voltage, ensuring optimized performance across all supply voltage values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the interface electronic circuit is optimized for low voltage operation, then power consumption is reduced, but the Acoustic Overload Point (AOP) and Power-Supply Rejection Ratio (PSRR) performance deteriorates
Solution Approach 1:
The patent implements dynamic adaptation by detecting the actual supply voltage level and automatically switching between different operating modes (first mode for low voltage, second mode for high voltage). This allows the circuit to optimize its performance parameters (AOP, PSRR) based on the available supply voltage, rather than being fixed for a specific voltage range. The operating point of the amplifier stage is dynamically adjusted to match the supply conditions.
Solution Approach 2:
The patent changes operating parameters (such as amplifier biasing, reference voltages, and circuit configuration) based on the detected supply voltage level. By modifying these parameters according to the supply voltage, the circuit maintains optimal AOP and PSRR performance across different voltage conditions while accepting lower voltage supplies that reduce power consumption.
2Reliability
If the interface electronic circuit is optimized for high AOP, then the Acoustic Overload Point performance is improved, but the circuit requires higher supply voltage and cannot operate efficiently at low voltage
Solution Approach 1:
The circuit dynamically switches between operating modes based on supply voltage detection. When high supply voltage is available, it configures for high AOP performance. When low supply voltage is detected, it switches to a mode that accepts lower AOP but enables efficient low-voltage operation, thus adapting to power consumption requirements.
Solution Approach 2:
The interface electronic circuit is designed to perform multiple functions across different operating conditions. It can operate in a first mode optimized for low voltage (accepting lower AOP) and in a second mode optimized for high AOP when higher voltage is available. This multi-functionality allows the same circuit to serve both low-power and high-performance applications.
3Device complexity
If fixed reference voltages are used in the amplifier stage, then the circuit design is simplified, but the operating point cannot be adjusted to maintain performance across varying supply voltages
Solution Approach 1:
The circuit employs automatic detection of the supply voltage level and self-configures its operating mode without external intervention. The detection circuit monitors the supply voltage and automatically selects the appropriate operating mode (first or second mode), adjusting reference voltages and amplifier biasing accordingly. This self-service mechanism maintains performance consistency across varying supply voltages without adding significant design complexity.
Data Source
AI summary
In at least one embodiment, an interface electronic circuit for a capacitive acoustic transducer having a sensing capacitor is provided. The interface electronic circuit includes an amplifier, a voltage regulator, a common-mode control circuit, and a reference generator. The amplifier has an input coupled to an electrode of the sensing capacitor. The voltage regulator is configured to receive a regulator reference voltage, generate a regulated voltage based on the regulator reference voltage, and supply the regulated voltage to a supply input of the amplifier. The common-mode control circuit controls a common-mode voltage present on the input of the amplifier based on a common-mode reference voltage. The reference generator receives a supply voltage and generates the regulator reference voltage and the common-mode reference voltage with respective values that are variable as a function of the supply voltage.