Stimulating Electrode Current Calibration for Source-Sink Matching
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Solution Overview
Problem
Current stimulating medical devices face challenges in maintaining accurate current matching between current sources and sinks over time due to operational parameter drift, which can lead to toxic product accumulation and tissue damage.
Innovation Solution
In situ calibration of current sources and sinks using a calibration arrangement that compares and adjusts the operational parameters of Digital-to-Analog Converters (DACs) to ensure matched currents, reducing the risk of toxic product accumulation and maintaining effective stimulation strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current sources and sinks operate without calibration over time, then device complexity is reduced, but current matching accuracy deteriorates leading to toxic product accumulation
Solution Approach 1:
The calibration arrangement enables the device to automatically calibrate itself by comparing currents from multiple sources and sinks, adjusting operational parameters without external intervention. This self-calibration mechanism maintains current matching accuracy while minimizing the need for external calibration equipment or procedures.
Solution Approach 2:
The system implements a feedback loop where the calibration arrangement continuously monitors current matching between sources and sinks, compares actual currents against target values, and adjusts operational parameters accordingly. This closed-loop control ensures sustained current matching accuracy over the device lifetime.
2Measurement precision
If operational parameters of DACs are adjusted frequently for calibration, then current matching accuracy is improved, but loss of time increases
Solution Approach 1:
The calibration arrangement performs preliminary calibration during device initialization or manufacturing, establishing baseline operational parameters for each DAC. This preliminary calibration reduces the need for frequent subsequent adjustments, minimizing calibration time while maintaining accuracy.
Solution Approach 2:
The system automatically detects when calibration is needed and performs self-calibration without requiring external intervention or significant user time. The calibration process is integrated into normal device operation, allowing it to occur during routine use rather than requiring separate calibration sessions.
3Adaptability or versatility
If separate current source and sink circuits are used, then adaptability of stimulation strategies is improved, but reliability deteriorates due to current mismatch
Solution Approach 1:
The calibration arrangement continuously monitors current output from each separate source and sink circuit, comparing actual currents against target values. When mismatches are detected, the system automatically adjusts operational parameters to restore balance, ensuring reliable current matching while preserving the flexibility of having separate circuits for different stimulation strategies.
Solution Approach 2:
The system dynamically adjusts operational parameters (such as DAC codes or current amplitudes) of individual sources and sinks based on real-time calibration data. This parameter adjustment capability allows each circuit to be independently optimized while maintaining overall current balance, preserving stimulation strategy adaptability while improving reliability.
Data Source
AI summary
A stimulating medical device, comprising a plurality of electrodes, and a current source and a current sink connected to each one of the electrodes. The medical device also comprises a calibration arrangement configured to compare the current provided by a selected one of the current sources to the current sunk by a selected one of the current sinks, and configured to adjust an operational parameter of at least one of the source and sink based on said comparison such that the current provided by the selected current source is substantially the same as the current sunk by the current sink.