Programmable Voltage Source for MEMS Microphone Distortion Reduction
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Solution Overview
Problem
Audio microphones, particularly MEMS microphones, face challenges in handling a wide dynamic range of sound pressure levels due to amplifiers and preamplifiers being optimized for specific ranges, leading to potential distortion when dealing with high-intensity acoustic signals.
Innovation Solution
A programmable voltage source system that includes a charge pump with multiple capacitors and clock generators, allowing for adjustable bias voltage to be provided to MEMS microphones, enabling fine and coarse voltage control through a switching network and digital-to-analog converter, thereby adjusting the sensitivity and reducing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If amplifiers and preamplifiers are optimized for a particular dynamic range, then performance within that range is improved, but the system cannot handle the full audio range without adding significant distortion
Solution Approach 1:
The patent implements a programmable voltage source that dynamically adjusts the bias voltage applied to the MEMS microphone based on the acoustic signal level. The system includes a detector that monitors the acoustic signal and controls the voltage source to provide different bias voltages for different signal levels, enabling the system to adapt to the full dynamic range without distortion
Solution Approach 2:
The invention changes the bias voltage parameter of the MEMS microphone dynamically based on the acoustic signal level. By adjusting this electrical parameter in response to signal conditions, the system optimizes performance across the entire dynamic range from threshold of hearing to high-intensity sounds
2Ease of manufacture
If a fixed bias voltage is applied to MEMS microphones, then circuit design is simplified, but gain control and sensitivity adjustment are limited
Solution Approach 1:
The patent replaces the fixed bias voltage with a programmable voltage source that can be dynamically adjusted. The system includes control circuitry that programmably sets the bias voltage level, providing both manufacturing simplicity (through integration) and operational flexibility (through programmable control)
Solution Approach 2:
The programmable voltage source serves multiple functions: it provides the necessary bias voltage for MEMS operation, enables gain control, and allows sensitivity adjustment. This multi-functional component simplifies the overall circuit design while providing extensive control capabilities
Data Source
AI summary
In accordance with an embodiment, a method of operating a charge pump includes providing a first programmable voltage to a plurality of clock generators having outputs coupled to first nodes of corresponding groups of charge pump capacitors, and selecting a second node of one capacitor from one of the corresponding groups of charge pump capacitors. The clock generators produce a plurality of clock signals having amplitudes proportional to the first programmable voltage.