Implantable Stimulator Current DAC Architecture for Electrode Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current implantable pulse generators (IPGs) for spinal cord stimulation systems face challenges in efficiently delivering precise electrical stimuli due to limitations in their current generation architecture, which can lead to suboptimal tissue stimulation and inefficient power usage.
Innovation Solution
The proposed solution involves an improved ASIC architecture with a centralized master DAC and distributor circuitry that provides a scalable reference current to dedicated PDAC/NDAC pairs, allowing for precise control of anodic and cathodic currents at each electrode node, enabling independent calibration and amplification of stimulation currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional current generation architecture is used in IPG, then device simplicity is maintained, but current precision and power efficiency deteriorate
Solution Approach 1:
The current generation architecture is segmented into multiple functional blocks: master DAC block for reference current generation, distributor block for current allocation, and multiple PDAC/NDAC pairs for precise electrode current control. This segmentation enables independent optimization of each block, achieving high current precision while maintaining manageable device complexity through modular design.
Solution Approach 2:
A centralized master DAC and distributor circuitry are introduced as intermediary components between the power source and electrode nodes. The master DAC generates a precise reference current that is then distributed and calibrated to multiple electrode nodes, enabling precise current control without requiring complex independent control circuits at each electrode, thus resolving the contradiction between precision and complexity.
2Use of energy by moving object
If traditional current generation architecture is used in IPG, then device simplicity is maintained, but power efficiency deteriorates
Solution Approach 1:
The master DAC block generates a calibrated reference current in advance, which is then distributed to multiple PDAC/NDAC pairs. This preliminary generation and calibration of reference current eliminates the need for multiple independent high-power DACs, significantly reducing overall power consumption while maintaining precise current control capability at each electrode node.
Solution Approach 2:
The master DAC and distributor circuitry serve multiple functions: generating reference current, calibrating electrode currents, and distributing current to multiple electrodes. This multi-functionality consolidates what would otherwise require multiple separate power-intensive circuits, improving power efficiency without sacrificing control precision.
3Measurement precision
If centralized master DAC architecture is implemented, then current precision is improved, but device complexity increases
Solution Approach 1:
The system is divided into distinct functional blocks (master DAC, distributor, PDAC/NDAC pairs) that can be independently designed, calibrated, and optimized. This segmentation allows the complex precision current control function to be distributed across manageable modules, reducing the practical complexity burden while maintaining high precision.
4Manufacturing precision
If independent calibration of each electrode is enabled, then stimulation precision is improved, but device complexity increases
Solution Approach 1:
Independent calibration of each electrode is performed during the manufacturing process using the master DAC-generated reference current. This preliminary calibration stores optimal current parameters for each electrode in memory, enabling precise stimulation without requiring complex real-time adjustment circuits during operation, thus achieving high precision while managing device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables more efficient and precise delivery of stimulation currents, optimizing tissue stimulation while minimizing power consumption and ensuring consistent performance across a wide range of current amplitudes, thereby enhancing the therapeutic efficacy of spinal cord stimulation.
Implementation Method 1
a first digital-to-analog converter (DAC) configured to receive digital data specifying a magnitude of a total anodic current amplitude to be produced at the electrode nodes, and to produce a first current with a magnitude indicative of the total anodic current amplitude
Implementation Method 2
a plurality of first calibration circuits each configured to receive the first current, wherein each of the first calibration circuits is controllable to produce a different second current as a function of the first current
Implementation Method 3
each second DAC is configured when selected to amplify its received second current to produce an anodic stimulation current at its associated electrode node
Data Source
AI summary
Digital-to-Analog (DAC) circuitry for an implantable pulse generator is disclosed which is used to program currents at the electrodes. Calibration circuitry allows the positive and negative currents produced at each electrode to be independently calibrated to achieve an ideal (linear) response across a range of amplitude values provided to the DAC circuitry by a digital amplitude bus. The calibration circuitry includes electrode gain and electrode offset circuitry for each of the electrodes. Current range DAC circuitry is also provided which can be used to adjust the gain and offset current at all of the electrodes. The current range DAC circuitry is particularly useful when spanning a range of therapeutic currents for a patient, and allows all possible amplitude values provided by the digital bus to be used to span the range. This can improve (reduce) the current resolution of the electrode currents with each amplitude value step.