Digital Microphone Gain Circuit With Lookup-Table Feedback
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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 gain adjustments 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 lookup table-based digital gain implementation. The lookup table stores pre-calculated gain values, allowing the system to switch between gain modes by simply selecting different table entries rather than performing complex real-time calculations, thereby reducing power consumption while maintaining gain adjustment functionality
Solution Approach 2:
The patent pre-calculates and stores gain values in a lookup table before operation. By preparing gain values in advance and storing them in memory, the system eliminates the need for complex real-time gain calculations during operation, significantly reducing power consumption while maintaining the ability to provide multiple gain modes
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 compact lookup table implementation. Instead of requiring large arrays of multipliers and adders for real-time gain calculation, the system uses a small memory structure to store pre-computed gain values, dramatically reducing the integrated circuit area required for gain adjustment functionality
Solution Approach 2:
The patent uses a lookup table that stores copies of pre-calculated gain values. Rather than implementing complex calculation hardware, the system creates a digital copy of all possible gain values and stores them in memory, allowing instant retrieval with minimal circuitry and occupying significantly less silicon area
3Reliability
If high performance digital microphone is implemented, then high linearity and signal-to-noise ratios are achieved, but power consumption and integrated circuit area increase
Solution Approach 1:
The patent pre-calculates gain values with high precision and stores them in a lookup table. By performing the computationally intensive gain calculations in advance during manufacturing or initialization, the system achieves high linearity and signal-to-noise ratio performance while consuming minimal power during actual operation, as only simple table lookups are required
Data Source
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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.