Implantable Stimulator Current Steering With Master DAC Distribution
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Solution Overview
Problem
Current implantable pulse generators (IPGs) for spinal cord stimulation systems face challenges in efficiently managing stimulation currents across multiple electrodes, leading to inefficiencies and potential tissue damage due to the complexity of current steering and compliance voltage management.
Innovation Solution
The improved IPG architecture incorporates a centralized master Digital-to-Analog Converter (DAC) with a distributor that scales a reference current and sends it to dedicated P-channel and N-channel DAC pairs, allowing for precise control of stimulation currents across electrodes, and includes a Pulse Definition Circuit to manage overlapping stimulation pulses, thereby optimizing current distribution and compliance voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional IPG architecture with separate microcontroller and ASIC is used, then device functionality is achieved, but current steering control precision deteriorates and compliance voltage management becomes inefficient
Solution Approach 1:
The patent integrates the microcontroller and ASIC into a single unified integrated circuit device. This merging eliminates the need for separate components and their interconnections, simplifying the overall architecture while enabling more precise current steering control through integrated DAC circuits and reduced signal path complexity.
Solution Approach 2:
The integrated circuit device performs multiple functions including microcontroller operations, DAC conversion, current steering control, and compliance voltage management within a single component. This multi-functionality reduces the total number of components needed while improving control precision through coordinated operation of all functions in one device.
2Measurement precision
If multiple dedicated DAC pairs are used for each electrode, then current control precision improves, but device complexity and power consumption increase
Solution Approach 1:
Instead of using separate dedicated DAC pairs for each electrode, the patent merges multiple DAC functions into a single integrated DAC circuit within the unified IC device. This consolidation maintains precise current control for multiple electrodes while reducing the total number of DAC components, thereby lowering power consumption and device complexity.
Solution Approach 2:
The integrated DAC circuit performs multiple DAC conversion functions for different electrodes through a single multi-functional component. This universal DAC can be dynamically configured to serve different electrode pairs, providing precise current control without the power penalty of having separate dedicated DACs for each electrode.
3Reliability
If complex current steering management is implemented, then therapeutic efficacy improves, but risk of tissue damage increases due to improper current distribution
Solution Approach 1:
The integrated circuit device incorporates feedback mechanisms that monitor current distribution across electrodes and adjust DAC output accordingly. This real-time feedback ensures optimal current steering for therapeutic efficacy while preventing excessive current density that could cause tissue damage, thereby improving safety alongside effectiveness.
Solution Approach 2:
The system dynamically adjusts current distribution across electrodes based on real-time conditions through the integrated control architecture. This dynamic current steering capability allows the system to optimize therapeutic delivery while automatically preventing harmful current concentrations, adapting to changing tissue conditions without manual intervention.
Data Source
AI summary
An implantable pulse generator (IPG) is disclosed having an improved ability to steer anodic and cathodic currents between the IPG's electrodes. Each electrode node has at least one PDAC/NDAC pair to source/sink or sink/source a stimulation current to an associated electrode node. Each PDAC and NDAC receives a current with a magnitude indicative of a total anodic and cathodic current, and data indicative of a percentage of that total that each PDAC and NDAC will produce in the patient's tissue at any given time, which activates a number of branches in each PDAC or NDAC. Each PDAC and NDAC may also receive one or more resolution control signals specifying an increment by which the stimulation current may be adjusted at each electrode. The current received by each PDAC and NDAC is generated by a master DAC, and is preferably distributed to the PDACs and NDACs by distribution circuitry.