Implantable Stimulator Current DAC Calibration for Multi-Electrode Accuracy
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Solution Overview
Problem
Existing implantable pulse generator (IPG) architectures face challenges in efficiently and accurately delivering electrical stimuli to multiple electrodes, particularly due to manufacturing variations and non-idealities that affect current delivery accuracy and resolution, limiting therapeutic efficacy.
Innovation Solution
The proposed architecture incorporates a centralized master digital-to-analog converter (DAC) and distributor circuitry, along with electrode-specific calibration circuits, to independently calibrate and control current delivery to each electrode, ensuring precise and adjustable stimulation currents within a therapeutic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional IPG architecture with monolithic integrated circuits is used, then the device structure is simple and manufacturing is easier, but current delivery accuracy and resolution are limited due to manufacturing variations and non-idealities
Solution Approach 1:
The patent divides the IPG architecture into separate functional modules: a microcontroller unit and a dedicated stimulator integrated circuit. This segmentation allows each module to be optimized independently - the microcontroller handles control logic while the stimulator IC focuses on precise current generation and delivery, thereby improving current delivery accuracy without excessively complicating the overall device structure.
Solution Approach 2:
The patent introduces a distributor circuit as an intermediary component between the microcontroller and the stimulator IC. This distributor acts as a mediator that receives control signals from the microcontroller and distributes them to appropriate stimulator channels, enabling precise control of current delivery to multiple electrodes while maintaining a manageable device architecture.
2Measurement precision
If electrode-specific calibration circuits are added to each electrode node, then current delivery accuracy and flexibility are enhanced, but device complexity and number of components increase
Solution Approach 1:
The patent implements calibration circuits at the stimulator IC level that can serve multiple electrode channels through a distributed architecture. Rather than requiring completely independent calibration circuits for each electrode, the system uses a universal calibration mechanism that can be selectively applied to different electrode channels as needed, thereby improving measurement precision while controlling device complexity through resource sharing.
Solution Approach 2:
The patent employs digital-to-analog converters (DACs) that enable precise control of stimulation current parameters through digital programming. By changing digital control parameters rather than physically reconfiguring hardware, the system achieves high current delivery accuracy and flexibility without proportionally increasing the number of physical components. The DAC-based approach allows software-configurable calibration and control for each electrode channel.
3Ease of operation
If a centralized master DAC and distributor circuitry are used, then control of stimulation parameters is improved, but circuit complexity increases
Solution Approach 1:
The patent combines the master DAC and distributor circuitry into an integrated stimulator IC that works in conjunction with the microcontroller. By merging these functions into a unified integrated circuit rather than separate discrete components, the system achieves ease of operation through centralized digital control while actually reducing overall circuit complexity through integration and modular design.
Data Source
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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.