Implantable Pulse Generator Voltage Domain Conversion Circuitry
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Solution Overview
Problem
Conventional implantable pulse generators for medical devices, such as pacemakers and neurostimulation systems, face challenges in safely switching high voltage signals without damaging the oxide layers of transistors, as they typically employ thick-oxide gates to prevent physical damage from excessive voltages.
Innovation Solution
The use of thin-oxide transistors in pulse generating circuitry, divided into different voltage domains with specific logic levels for gating, and conversion circuitry with cross-coupled transistors to generate rail-to-rail outputs, ensures that voltage differences between the gate and source are maintained within safe ranges to prevent oxide layer damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick-oxide gates are used to prevent physical damage from excessive voltages, then transistor reliability is improved, but device complexity and power consumption increase
Solution Approach 1:
The circuit is divided into multiple voltage domains (first voltage domain with first logic level, second voltage domain with second logic level) with different voltage levels. Each domain uses transistors optimized for its specific voltage range, allowing thin-oxide transistors to be used in the high-voltage pulse generation domain while thick-oxide transistors are used in the control domain, thus resolving the contradiction between reliability and complexity
Solution Approach 2:
Different regions of the circuit are assigned different oxide thickness characteristics based on their functional requirements. The pulse generating circuitry uses thin-oxide transistors for high-voltage switching where speed is critical, while control circuitry uses thick-oxide transistors for reliability. This local differentiation allows the system to achieve both high reliability and low complexity
2Reliability
If thick-oxide transistors are used to switch high voltage signals, then transistor reliability is improved, but pulse generation efficiency deteriorates
Solution Approach 1:
The system segments transistor usage by voltage domain and function. Thin-oxide transistors are deployed specifically in the pulse generating circuitry where high-speed switching is required, while thick-oxide transistors are used in control circuitry where reliability is paramount. This segmentation allows each transistor type to operate in its optimal performance regime
Solution Approach 2:
The circuit employs local quality differentiation by using thin-oxide transistors in the high-voltage pulse generation region where switching speed is critical for efficiency, and thick-oxide transistors in the control region where reliability is paramount. This spatial differentiation of transistor characteristics resolves the contradiction between reliability and productivity
3Productivity
If thin-oxide transistors are used in high voltage domains, then pulse generation efficiency is improved, but transistor damage from excessive voltage increases
Solution Approach 1:
The system segments the circuit into distinct voltage domains separated by conversion circuitry. Thin-oxide transistors are confined to the high-voltage pulse generation domain where they provide efficient switching, while the control domain operates at lower voltages suitable for thin-oxide transistors. The voltage domain segmentation prevents excessive voltage from reaching the thin-oxide transistors in the control circuitry
Solution Approach 2:
Voltage domain conversion circuitry acts as an intermediary between the control circuitry and the pulse generating circuitry. This conversion circuitry translates control signals from the low-voltage domain to the high-voltage domain, protecting the thin-oxide transistors in the control circuitry from exposure to damaging high voltages while enabling efficient pulse generation in the high-voltage domain
Data Source
AI summary
In one embodiment, an implantable pulse generator (IPG) for generating electrical pulses for stimulation of tissue of a patient, comprises: a controller for controlling operations of the IPG; pulse generating circuitry for generating electrical pulses; and conversion circuitry for converting a received logic signal generated by a first voltage domain for provision to a second voltage domain, the conversion circuitry comprising a first stage and a second stage, wherein (i) the first stage receives first signals at first and second logic levels; (ii) the second stage receives second signals at third and fourth logic levels, (iii) the second stage comprising two sets of cross-coupled transistors for generating a rail-to-rail output at the third and fourth logic levels according to whether the received logic signal is at the first or second logic level.