Dynamic Incremental SAR ADC for In-Ear Biosignals
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Solution Overview
Problem
Conventional SAR ADCs are inefficient for slowly varying signals with substantial low-frequency content and infrequent large fast transients, requiring numerous conversion cycles and prone to errors due to DAC charge loss and signal amplitude dependence.
Innovation Solution
The dynamic incremental-SAR (iSAR) ADC adjusts the search region dynamically using a variable radix-2 base, reducing the number of conversion cycles independent of signal amplitude and correcting errors, allowing for efficient conversion of slowly varying signals with adaptive start index and overflow protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SAR ADC is used for slowly varying signals with low-frequency content, then conversion accuracy can be maintained, but the number of conversion cycles increases substantially and energy consumption increases
Solution Approach 1:
The patent implements dynamic incremental SAR ADC that adapts the conversion process based on signal characteristics. The system dynamically adjusts the number of conversion cycles and step size according to the rate of signal change, using fewer cycles for slowly varying signals while maintaining accuracy for fast transients, thereby resolving the contradiction between conversion accuracy and productivity
Solution Approach 2:
The patent changes the conversion parameters dynamically based on signal conditions. It modifies the conversion cycle count, step size, and acquisition time according to the detected signal characteristics, allowing the system to optimize between accuracy and efficiency for different signal types and rates of change
2Adaptability or versatility
If conventional SAR ADC is used for signals with infrequent large fast transients, then full dynamic range can be captured, but the system becomes prone to errors due to DAC charge loss and signal amplitude dependence
Solution Approach 1:
The patent employs feedback mechanisms where the ADC system monitors signal characteristics and adjusts its operation accordingly. The feedback loop detects signal amplitude and rate of change, then modifies conversion parameters to prevent DAC charge loss errors and maintain accuracy across the full dynamic range, resolving the reliability issue while preserving adaptability
Solution Approach 2:
The system performs preliminary signal assessment before conversion to determine appropriate conversion parameters. By pre-detecting signal characteristics such as amplitude and transient content, the system can configure the conversion process in advance to avoid errors from DAC charge loss and signal amplitude dependence
3Measurement precision
If conventional SAR ADC requires numerous conversion cycles for accurate conversion, then measurement precision can be maintained, but energy consumption increases substantially
Solution Approach 1:
The patent applies partial action by performing only the necessary number of conversion cycles required to achieve the desired precision for each specific signal. Instead of always executing full conversion cycles, the system dynamically determines the minimum cycles needed based on signal characteristics, thereby maintaining ADC resolution precision while substantially reducing energy consumption for slowly varying signals
Data Source
AI summary
In some implementations, the current subject matter relates a system including an in-ear housing configured to fit in an ear of a wearer; a flexible printed circuit mounted within the in-ear housing; and an analog to digital converter comprising a neural interface system-on-chip having dynamic incremental successive-approximation register acquisition to process signals detected by at least one electrode disposed on or near a surface of the in-ear housing. Related systems, methods, and articles of manufacture are also disclosed.