Multi-Electrode Implantable Stimulator Capacitor Architecture
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Solution Overview
Problem
Multi-electrode implantable stimulators face challenges in minimizing device size while ensuring patient safety, particularly during current steering, due to the need for multiple decoupling capacitors which occupy significant space and can lead to direct DC current injection into the tissue.
Innovation Solution
The design incorporates a minimal number of decoupling capacitors, with either X capacitors in the cathode paths or one in the anode path and X-1 in the cathode paths, allowing for safe current steering by using X individually-controllable DACs to prevent DC current injection, even when activating multiple cathodes or anodes simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple decoupling capacitors are used in multi-electrode implantable stimulators, then patient safety is ensured during current steering, but device size increases significantly
Solution Approach 1:
The patent combines multiple decoupling capacitors into a single shared decoupling capacitor that serves multiple electrodes. This is achieved by configuring the capacitor to be electrically connected to a common reference node that multiple electrodes can access, allowing the same capacitor to prevent DC current injection for all electrodes simultaneously, thereby reducing the total number of capacitors from N to 1
Solution Approach 2:
The single decoupling capacitor is designed to perform multiple functions across different electrode configurations. It universally prevents DC current injection regardless of which electrode is active, serving as a shared safety mechanism for all electrodes rather than having dedicated capacitors for each electrode
2Volume of stationary object
If a minimal number of decoupling capacitors is used, then device size is reduced, but the risk of DC current injection into tissue increases
Solution Approach 1:
The patent introduces a switched capacitor configuration as an intermediary mechanism between the current source and the electrodes. This switched capacitor acts as a dynamic decoupling element that can be selectively connected to different electrodes through switch matrices, providing DC blocking functionality with a single physical capacitor rather than requiring multiple capacitors
3Reliability
If multiple decoupling capacitors are implemented, then DC current injection is prevented, but device complexity increases
Solution Approach 1:
The patent merges multiple decoupling capacitor functions into a single physical capacitor component. By sharing one capacitor across multiple electrode paths and using switch matrices to connect the capacitor to different electrodes as needed, the design reduces component count and simplifies the overall circuit architecture while maintaining DC current prevention capability
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 reduces the device size by minimizing the number of capacitors required, ensuring no DC current injection during current steering, thus enhancing therapeutic flexibility and safety.
Implementation Method 1
decoupling or blocking capacitors 42 and 44 hardwired to the anode and cathode respectively... such decoupling capacitors only allow the passage of AC components of the current provided by the DAC 20, and thus prevent the DC injection of current into the patient's tissue R
Implementation Method 2
Current flows by operation of a current source 20, which typically comprises a Digital-to-Analog Converter, or 'DAC' 20, which is programmable to provide a desired therapeutic current, Iout, to the patient's tissue R
Implementation Method 3
A DC-DC converter 22 is used to boost Vbat to the desired compliance voltage V+
Data Source
AI summary
Architectures for implantable stimulators having N electrodes are disclosed. The architectures contains X current sources, or DACs. In a single anode/multiple cathode design, one of the electrodes is designated as the anode, and up to X of the electrodes can be designated as cathodes and independently controlled by one of the X DACs, allowing complex patient therapy and current steering between electrodes. The design uses at least X decoupling capacitors: X capacitors in the X cathode paths, or one in the anode path and X−1 in the X cathode paths. In a multiple anode/multiple cathode design having X DACs, a total of X−1 decoupling capacitors are needed. Because the number of DACs X can typically be much less than the total number of electrodes (N), these architectures minimize the number of decoupling capacitors which saves space, and ensures no DC current injection even during current steering.