Stimulator Sensing Circuitry for DC Offset Compensation
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Solution Overview
Problem
Implantable neurostimulator devices face challenges in accurately sensing tissue signals due to DC offset voltages that can cause saturation or clipping of digitized waveforms, affecting the effectiveness of stimulation and signal detection.
Innovation Solution
The implementation of sense amplifier circuitry with control circuitry to sense and measure DC offset voltages, followed by the application of offset removal currents or adjustments to stimulation parameters to reduce or eliminate these offsets, using algorithms to iteratively manage and compensate for DC offset voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC offset compensation is not implemented, then the device complexity remains low, but the measurement precision of tissue signals deteriorates due to saturation or clipping of digitized waveforms
Solution Approach 1:
The system performs preliminary DC offset measurement and compensation before tissue signal sensing. The control circuitry measures the DC offset voltage at the sense amplifier inputs and applies compensation currents to remove the offset before actual tissue signal acquisition, preventing saturation and clipping of digitized waveforms
Solution Approach 2:
The system implements a feedback mechanism where the control circuitry continuously monitors the DC offset voltage at the sense amplifier inputs and dynamically adjusts compensation currents. The algorithm iteratively manages and compensates for DC offset voltages based on real-time measurements, ensuring accurate tissue signal sensing
2Measurement precision
If DC offset compensation circuitry is added, then the measurement precision improves, but the device complexity increases due to additional circuitry and algorithms
Solution Approach 1:
The control circuitry performs multiple functions: it measures DC offset voltages, generates compensation currents, and manages the overall sensing operation. The sense amplifier circuitry serves both for DC offset measurement and tissue signal sensing, reducing the need for separate dedicated circuits
Solution Approach 2:
The system uses its own sense amplifier circuitry to measure and compensate for DC offset voltages without requiring external calibration equipment. The control circuitry automatically manages the compensation process through integrated algorithms that operate within the implantable device itself
Data Source
AI summary
DC offset compensation is provided to equate the DC values of the inputs to sense amp circuitry used to sense tissue signals in a stimulator device. When a DC offset is present at the inputs to the sense amp circuitry, the stimulation circuitry is controlled to remove this DC offset, which can occur in different ways. In one example, charge imbalanced pulses are provided to the inputs of the sense amp circuitry, the stimulation electrodes, or to other electrodes. Control of the stimulation circuitry can occur using a DC offset compensation algorithm programmed into control circuitry of the stimulator device. Using the algorithm, measurements indicative of the DC offset are used to determine charge imbalanced pulses, with the measurements being made by shorting the inputs together, and then releasing the input to reestablish the DC offset.