Comparator Level Shifting for Wide CMIR and Oxide Stress Protection
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Solution Overview
Problem
Process node scaling reduces gate oxide thickness in transistors, leading to lower oxide breakdown voltages, which limits the common mode input range (CMIR) of comparators and can cause gate oxide stress or damage from input signals exceeding the breakdown voltage, while existing solutions with external components increase costs and system size and compromise performance.
Innovation Solution
A comparator design incorporating a level shifter and body bias controller to mitigate gate oxide stress by applying voltage shifts and dynamically adjusting body bias, respectively, without adding external components, thereby supporting a wide input voltage range and CMIR while maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If gate oxide thickness is reduced for process node scaling, then circuit speed and power efficiency are improved, but oxide breakdown voltage decreases and common mode input range is limited
Solution Approach 1:
The patent introduces a level shifter circuit as an intermediary component between the comparator input and the transistor gate. This level shifter translates the input common mode voltage to a safe voltage range that does not exceed the reduced oxide breakdown voltage, while still allowing the comparator to function correctly. The level shifter acts as a mediator that protects the thin gate oxide from high voltage stress while maintaining the desired input voltage range functionality.
2Adaptability or versatility
If external components are added to expand input voltage range, then common mode input range is improved, but device complexity and system size increase
Solution Approach 1:
The patent merges the level shifter functionality directly into the comparator circuit structure. Rather than adding separate external components, the level shifter is integrated using transistors that are part of the comparator's internal architecture. This integration achieves the voltage range expansion while minimizing increases in device complexity and system size.
Solution Approach 2:
The level shifter circuit performs multiple functions: it translates the input common mode voltage to protect the gate oxide, it maintains the differential signaling integrity, and it enables the comparator to operate across a wide input voltage range. By combining these functions into a single integrated circuit block, the patent avoids the need for multiple separate external components.
3Adaptability or versatility
If external components are added to expand input voltage range, then common mode input range is improved, but manufacturing cost increases
Solution Approach 1:
The level shifter is integrated into the comparator circuit, allowing both functions to be manufactured together in a single semiconductor fabrication process. This integration eliminates the need for separate external components and reduces assembly steps, thereby lowering manufacturing costs while achieving the expanded common mode input range.
Data Source
AI summary
A circuit includes a transistor input pair, a differential input having a comparator input, and a level shifter. The transistor input pair is adapted to be coupled between a voltage supply and a comparator output. The transistor input pair includes a first transistor having a gate and a drain. The drain of the first transistor is coupled to the comparator output. The level shifter is coupled between the transistor input pair and the differential input. The level shifter includes a second transistor having a gate and a source. The gate of the second transistor is coupled to the comparator input. The source of the second transistor is coupled to the gate of the first transistor.