Level Shifting Circuit With Limited Output Swing for Oxide Protection
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Solution Overview
Problem
Level shifting circuits face challenges in minimizing gate oxide breakdown and unnecessary stress on semiconductor components due to voltage swings between different operating voltage ranges, which can lead to reduced switching speed and increased manufacturing complexity.
Innovation Solution
Incorporating an output voltage controlling circuit that limits the output voltage swing to an intermediate range between the high and low supply voltages, allowing semiconductor components to operate within a narrower voltage range similar to the core circuit, thus avoiding excessive stress and enabling same-manufacturing-process compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If level shifting circuits transfer signals between different operating voltage ranges, then voltage level compatibility is improved, but gate oxide breakdown and stress on semiconductor components increase
Solution Approach 1:
The patent introduces an intermediate voltage range (between the low core voltage and high I/O voltage) as a mediator for the output signal. The level shifting circuit includes an output control circuit that limits the output voltage to this intermediate range, preventing direct exposure to the full high voltage swing. This intermediary voltage zone acts as a buffer that protects the core circuit's gate oxide while still enabling voltage level translation functionality.
2Adaptability or versatility
If level shifting circuits transfer signals between different operating voltage ranges, then voltage level compatibility is improved, but manufacturing complexity increases
Solution Approach 1:
The patent employs homogeneity by using the same gate oxide thickness for both the core circuit transistors and the level shifting circuit transistors. The output control circuit ensures that even though the level shifter operates with higher voltage swings, the actual voltage stress on the gate oxide remains within the same safe range as the core circuit. This allows both circuits to be manufactured using identical process parameters, simplifying manufacturing while maintaining voltage level translation capability.
3Reliability
If level shifting circuits use thicker gate oxide to prevent breakdown, then reliability is improved, but switching speed decreases
Solution Approach 1:
The patent changes the voltage range parameter for the output signal from the full high-voltage swing to a limited intermediate voltage swing. By controlling the output voltage to stay within this narrower intermediate range, the patent maintains the same gate oxide thickness as the core circuit while still providing protection against breakdown. This parameter change in voltage range allows fast switching speeds to be maintained without requiring thicker gate oxide.
Data Source
AI summary
A level shifting circuit includes a first circuit, a second circuit and an output voltage controlling circuit. The first circuit is coupled to an input node, an output node and a first supply voltage node and configured to pull an output voltage at the output node toward the first supply voltage in accordance with an input voltage applied to the input node. The second circuit is coupled to the first circuit, the output node and the second supply voltage node and configured to pull the output voltage toward the second supply voltage in accordance with the input voltage from the first circuit. The output voltage controlling circuit is coupled to the output node and configured to control the output voltage within a range narrower than a range from the first voltage to the second voltage.