Master DAC Amplitude Bus for Implantable Stimulator Electrodes
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Solution Overview
Problem
Current implantable pulse generators (IPGs) for spinal cord stimulation systems face challenges in efficiently managing and distributing stimulation currents across multiple electrodes, leading to potential inefficiencies and limitations in treating chronic pain and other neurological disorders.
Innovation Solution
The improved IPG architecture incorporates a centralized master digital-to-analog converter (DAC) that sets the amplitude of stimulation via an amplitude bus, distributing a reference current scaled by the amplitude to dedicated PDAC/NDAC pairs for each electrode, allowing for precise control and distribution of anodic and cathodic stimulation currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional IPG architecture with separate control circuits for each electrode is used, then each electrode can be independently controlled, but the device complexity and power consumption increase
Solution Approach 1:
The patent merges the control functions for multiple electrodes into a single master DAC that generates a common reference current. This master DAC is shared across all electrodes, eliminating the need for separate control circuits for each electrode while maintaining independent control capability through individual current mirror circuits.
Solution Approach 2:
The master DAC serves multiple functions by providing a shared reference current to all electrode channels. This single component performs the role of what would traditionally require multiple separate DACs, reducing overall device complexity while enabling universal control across all electrodes.
2Productivity
If traditional current distribution methods are used in IPGs, then all electrodes can be stimulated, but power wastage increases due to inefficient current management
Solution Approach 1:
The current mirror circuits automatically distribute the reference current from the master DAC to individual electrodes based on their specific stimulation requirements. Each electrode channel self-regulates its current draw from the shared reference, eliminating the need for additional power management circuitry and reducing overall power wastage.
Solution Approach 2:
The system dynamically adjusts the reference current magnitude from the master DAC based on the total stimulation demand across all electrodes. By changing the reference current parameter in response to operational conditions, the system optimizes power efficiency while maintaining adequate stimulation coverage across all electrodes.
3Measurement precision
If multiple independent DACs are used for each electrode, then precise current control is achieved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent segments the current control function into two distinct parts: a shared master DAC that generates the reference current, and individual current mirror circuits at each electrode that precisely distribute this reference current. This segmentation maintains precision while reducing overall complexity compared to using independent DACs for each electrode.
Solution Approach 2:
The master DAC acts as an intermediary component that provides a common reference current to all electrode channels. This intermediary approach allows precise current control at each electrode through the current mirror circuits while avoiding the complexity of multiple independent DACs, as the master DAC serves as a central control point for all channels.
Data Source
Figure 1A~1C
Figure 2A
Figure 2B
AI summary
A pulse generator, comprising: a plurality of electrode nodes, each electrode node configured to be coupled to an electrode configured to contact a patient's tissue; a plurality of first digital-to-analog converters (DACs) each configured to receive a first current with a magnitude indicative of a first total anodic current amplitude to be produced at the electrode nodes in a first timing channel, wherein each of the first DACs is configured when selected to provide a first anodic stimulation current to only a corresponding different one of the electrode nodes; and a plurality of second DACs each configured to receive a second current with a magnitude indicative of a second total anodic current amplitude to be produced at the electrode nodes in a second timing channel, wherein each of the second DACs is configured when selected to provide a second anodic stimulation current to only a corresponding different one of the electrode nodes.