Mixed Threshold Voltage Standard Cell Library Design
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Solution Overview
Problem
Standard cell libraries face decreased usefulness due to increased leakage current ratios between low and regular threshold voltage devices, particularly evident in 90 nm technology, which affects circuit design performance.
Innovation Solution
A standard cell library is developed with a mix of threshold voltage cells, including non-mixed and mixed threshold voltage cells, where mixed cells have different threshold voltages but the same footprint as regular cells, optimizing performance and reducing leakage by strategically combining low and regular threshold voltage devices within cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If low threshold voltage devices are used to improve performance, then speed and timing are improved, but leakage current increases significantly
Solution Approach 1:
The patent applies local quality by assigning different threshold voltages to different transistors within the same standard cell based on their specific functional requirements. Critical transistors that require fast switching are given low threshold voltage, while non-critical transistors use regular threshold voltage to minimize leakage. This selective approach allows performance optimization in critical paths without incurring the full leakage penalty of using low threshold voltage devices throughout the entire cell.
Solution Approach 2:
The patent segments the standard cell library into multiple types: regular threshold voltage cells, low threshold voltage cells, and hybrid cells with mixed threshold voltage devices. This segmentation allows designers to choose the appropriate cell type based on specific design requirements, balancing performance and leakage considerations for different portions of the circuit.
2Loss of energy
If regular threshold voltage cells are used, then leakage current is reduced, but performance and speed are degraded
Solution Approach 1:
The patent applies local quality by assigning different threshold voltages to different transistors within the same standard cell based on their specific functional requirements. Critical transistors that require fast switching are given low threshold voltage, while non-critical transistors use regular threshold voltage to minimize leakage. This selective approach allows performance optimization in critical paths without incurring the full leakage penalty of using low threshold voltage devices throughout the entire cell.
3Loss of energy
If mixed threshold voltage cells are created, then both performance and leakage are optimized, but device complexity increases
Solution Approach 1:
The patent creates universal standard cell templates that can accommodate multiple threshold voltage configurations. The same basic cell layout and interconnection structure can be instantiated with different combinations of low and regular threshold voltage devices depending on the specific design needs. This multi-functionality reduces the overall complexity by reusing proven cell designs rather than creating entirely new complex structures for each configuration.
Data Source
AI summary
The present invention provides a system and method for providing a standard cell library for reduced leakage and improved performance. The standard cell library comprises at least two sets of threshold voltage cells. At least one of the sets includes non-mixed threshold voltage cells. At least one of the sets includes mixed threshold voltage cells. The mixed threshold voltage cells have at least one threshold voltage cell having a first threshold voltage and a second threshold voltage cell having a second threshold voltage. The first and second threshold voltages are different. The mixed threshold voltage cells have substantially the same footprint as the non-mixed threshold voltage cell.