Digital Microphone Gain Circuit With Feedback LUT Adjustment
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Solution Overview
Problem
Existing digital microphones face challenges in reducing power consumption and integrated circuit area while maintaining high performance and compliance with customer requirements for high linearity and signal-to-noise ratios, particularly in cost-sensitive consumer device applications.
Innovation Solution
The implementation of a digital microphone system that includes an analog-to-digital converter (ADC) and a digital modulator with a feedback path featuring a first digital gain stage having an adjustable gain range, allowing for efficient gain adjustment by changing the feedback level and utilizing a lookup table for fine-tuning, which reduces the need for shift and add structures, thereby minimizing power consumption and silicon area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional digital gain implementation is used in digital microphones, then gain adjustment functionality is provided, but power consumption and integrated circuit area increase
Solution Approach 1:
The patent replaces traditional mechanical or complex digital gain adjustment mechanisms with a simplified digital implementation that uses a lookup table stored in memory. The gain values are pre-calculated and stored, allowing the system to switch between gain modes by simply retrieving different values from memory rather than performing complex real-time calculations, thereby reducing power consumption while maintaining full gain adjustment functionality
Solution Approach 2:
The patent pre-calculates and stores gain values in a lookup table during the design or initialization phase. This preliminary action eliminates the need for complex real-time gain calculations during operation, as the system only needs to retrieve pre-computed values from memory based on the desired gain mode, significantly reducing operational power consumption
2Adaptability or versatility
If traditional digital gain implementation is used in digital microphones, then gain adjustment functionality is provided, but integrated circuit area increases
Solution Approach 1:
The patent replaces complex digital gain calculation circuits with a memory-based lookup table approach. Instead of implementing multiple digital multipliers, adders, and control logic for real-time gain calculation, the system stores pre-computed gain values in memory and retrieves them as needed, dramatically reducing the integrated circuit area required for gain adjustment functionality
Solution Approach 2:
The patent uses a digital copy of gain values stored in memory rather than implementing the full computational machinery to calculate these values in real-time. The lookup table contains copies of pre-calculated gain factors that can be quickly retrieved and applied, eliminating the need for large areas of computational logic circuits
3Reliability
If high performance digital microphone is implemented, then linearity and signal-to-noise ratio are improved, but power consumption and integrated circuit area increase
Solution Approach 1:
The patent segments the gain adjustment functionality into discrete, pre-defined gain modes with specific gain values stored in the lookup table. This segmentation allows the high-performance digital microphone to offer multiple gain settings (e.g., different microphone modes, acoustic echo cancellation modes) without requiring continuous analog adjustment mechanisms, thereby maintaining high linearity and signal-to-noise ratio while reducing power consumption through efficient digital switching between predefined modes
Data Source
AI summary
A system includes an analog-to-digital converter (ADC) and a digital modulator coupled to the ADC, wherein the digital modulator comprises an output for providing a digital signal, wherein the digital modulator comprises a main signal path and a feedback path, and wherein the feedback path comprises a first digital gain stage having a first adjustable gain range.