Cross-Coupled Level Shifter for Threshold-Independent Signal Transfer
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Solution Overview
Problem
In semiconductor manufacturing, as technology scales down to 5 nm, 4 nm, or below, the need for a reliable level shifter arises to handle different voltage levels on the same printed circuit board, particularly to transfer 1.2V maximum applied voltage across 7 nm, 5 nm, 4 nm, or 3 nm chips, where existing solutions are inadequate due to varying transistor threshold voltages affecting output reliability.
Innovation Solution
A level shifter design incorporating a cross-coupled pair and a pull-down pair with p-channel metal-oxide-semiconductor field-effect transistors, along with control circuits and inverters, that decouples the output from transistor threshold voltage by using overdrive voltage and ground-level control signals, ensuring reliable signal transfer between different voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional level shifters are used with scaled-down transistors, then device scaling is achieved, but output reliability deteriorates due to varying transistor threshold voltages
Solution Approach 1:
The patent introduces a specialized pull-down pair consisting of first and second transistors that act as intermediaries between the input signal and the output nodes. These transistors are specifically configured to pull down the output nodes to the second voltage level, compensating for threshold voltage variations in scaled-down devices and ensuring reliable signal transfer.
Solution Approach 2:
The patent changes the operating parameters by applying overdrive voltage to the gates of the pull-down transistors. This overdrive voltage ensures that the transistors operate in a regime where their effective threshold voltage is overcome, providing consistent pull-down capability regardless of manufacturing variations in threshold voltage for scaled-down transistors.
2Reliability
If overdrive voltage is applied to ensure reliable signal transfer, then signal transfer reliability is improved, but power consumption increases
Solution Approach 1:
The level shifter uses periodic switching action through the cross-coupled pair and pull-down pair, where transistors are activated only when needed to transition between voltage levels. This reduces continuous power consumption while maintaining reliable signal transfer during transitions.
Solution Approach 2:
The circuit employs dynamic control where the cross-coupled pair and pull-down pair are activated based on the input signal state. The dynamic switching ensures that overdrive voltage is applied only when necessary for level transitions, optimizing the balance between reliability and power consumption.
Data Source
AI summary
A level shifter with high reliability is shown, which has a cross-coupled pair and a pull-down pair. The cross-coupled pair couples a first power terminal to a first output terminal of the level shifter or a second output terminal of the level shifter. The pull-down pair has a first transistor and a second transistor, which are controlled according to an input signal of the level shifter. The first transistor is coupled between the second output terminal and a second power terminal, and the second transistor is coupled between the first output terminal and the second power terminal. A first voltage level coupled to the first power terminal is greater than a second voltage level coupled to the second power terminal, and the second voltage level is greater than the ground level.