Single-Oxide Level Shifter for Fast Switching Without Gate Breakdown
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Solution Overview
Problem
Conventional level shifters using both thin and thick gate oxide MOS devices suffer from slow switching speed and complex manufacturing processes, leading to performance degradation and increased costs.
Innovation Solution
A level shifter design utilizing single gate oxide MOS devices with cross-coupled inverters and switch modules, eliminating the need for thick gate oxide devices by maintaining voltage differences across gate oxides below breakdown levels, allowing all MOS transistors to have the same thin gate oxide thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick gate oxide MOS devices are used in the level shifter, then gate oxide breakdown is prevented, but switching speed becomes slow
Solution Approach 1:
The patent applies different gate oxide thicknesses to different MOS devices based on their specific functional requirements. Thin gate oxide devices are used where high-speed switching is needed, while thick gate oxide devices are used only where high voltage withstand capability is critical. This localized differentiation resolves the contradiction by optimizing each component's properties for its specific role rather than using a uniform design.
Solution Approach 2:
The level shifter is segmented into multiple functional blocks (first inverter, second inverter, first switch module, second switch module) with different MOS device types. Each segment is designed with appropriate gate oxide thickness for its function, allowing the system to achieve both high speed and reliability through differentiated component design.
2Adaptability or versatility
If both thin gate oxide MOS devices and thick gate oxide MOS devices are used, then voltage level shifting is achieved, but manufacturing process becomes complex
Solution Approach 1:
The patent uses thin gate oxide MOS devices for all standard logic functions (inverters, switches) and reserves thick gate oxide devices only for specific high-voltage withstand locations. This localized approach maintains voltage level shifting capability while minimizing manufacturing complexity by reducing the variety of device types needed.
Solution Approach 2:
The patent combines multiple functional units (inverters and switch modules) into a single integrated level shifter structure. By merging these functions and using a predominantly thin gate oxide design with selective thick gate oxide elements, the patent simplifies the overall manufacturing process while maintaining the required voltage level shifting functionality.
3Speed
If thin gate oxide MOS devices are used throughout, then switching speed is improved, but gate oxide breakdown risk increases
Solution Approach 1:
The patent strategically places thick gate oxide devices only at specific locations where high voltage stress occurs (such as in the high-voltage side switches and inverters), while using thin gate oxide devices for all other functions. This localized protection approach maintains high switching speed overall while providing targeted reliability enhancement where breakdown risk exists.
Solution Approach 2:
The patent uses thick gate oxide devices as intermediary protective elements in high-voltage paths, allowing thin gate oxide devices to operate at high speeds in lower-stress regions. The thick gate oxide devices act as mediators that protect the system from breakdown while enabling the thin gate oxide devices to maintain their speed advantage.
Data Source
AI summary
A level shifter includes a first inverter coupled between the second voltage and the first voltage, and a second inverter coupled between the second voltage and the first voltage, the second inverter being cross-coupled with the first inverter for latching a value therein. A first switch module is coupled between a first data storage node of the first and second inverters and an input signal swinging between the first voltage and a ground voltage. A second switch module is coupled between a second data storage node of the first and second inverters and an inverted input signal swinging between the ground voltage and the first voltage. The first and second inverters and the first and second switch modules include one or more MOS transistors with gate oxide layers of the same thickness.