Two-Step Neural ADC for Fast Settling of Multiplexed Signals
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Solution Overview
Problem
Existing analog-to-digital conversion technologies face challenges in efficiently processing time division multiplexed analog signals with large variations in DC offsets, particularly in sensor systems like neural probes, where quick settling and tracking of signals are crucial for high-resolution sensing without causing tissue damage.
Innovation Solution
An ADC module configured to operate in both coarse and fine conversion phases, using delta modulation for tracking signals, where the coarse conversion phase quickly determines an initial approximation and the fine conversion phase further tracks the signal, allowing for quick settling and handling of large dynamic ranges, with components reused for compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If delta modulation is used in the ADC circuitry to achieve large dynamic range, then the dynamic range is improved, but the processing time increases before the modulator reaches the input voltage level of a new sub-sequence
Solution Approach 1:
The patent divides the ADC circuitry into two separate modulators: a first delta-sigma modulator optimized for coarse conversion with fast settling, and a second delta-sigma modulator optimized for fine conversion with high precision. This segmentation allows each modulator to be specialized for its specific function, resolving the contradiction between fast response and high precision by having both capabilities in separate components.
Solution Approach 2:
The first delta-sigma modulator performs preliminary coarse conversion to quickly establish the baseline voltage level before the second delta-sigma modulator performs fine conversion. This preliminary action enables the second modulator to start from a known reference point, reducing the time required to reach the input voltage level of new sub-sequences while maintaining high precision.
2Area of stationary object
If a single ADC circuitry is used to process multiple analog signals, then the circuitry area is reduced, but the ability to quickly settle on signals with large differing DC offsets deteriorates
Solution Approach 1:
The patent implements segmentation by creating two distinct modulator stages within the single ADC circuitry. The first modulator is dedicated to coarse conversion with optimized settling characteristics for handling large DC offset variations, while the second modulator handles fine conversion. This internal segmentation allows the compact single ADC to maintain fast settling speeds despite processing multiple signals with differing DC offsets.
Solution Approach 2:
Each modulator stage is designed with local quality optimized for its specific function: the first modulator has parameters optimized for fast settling and large dynamic range to handle DC offset variations, while the second modulator has parameters optimized for high precision fine conversion. This local optimization allows the overall system to maintain both compact size and fast settling performance.
Data Source
AI summary
An analog-to-digital converter, ADC, module is configured to operate in a coarse conversion ADC phase, and a fine conversion ADC phase comprising a delta modulation loop for tracking a signal, wherein the ADC module is configured to, at initiation of input of an analog signal, operate in the coarse conversion ADC phase for determining a coarse digital value; wherein the ADC module is configured to, when the coarse digital value is determined, operate in the fine conversion ADC phase, receive the coarse digital value as an initial approximation of the analog signal and track the analog signal during a finite duration.