Cell Library Sizing for Timing Closure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current digital circuit design methods based on cell libraries face challenges in achieving efficient timing closure due to limitations in generating a continuous spectrum of cell variants with varying drive strengths, P/N ratios, and topologies, which are crucial for high-performance integrated circuit design.
Innovation Solution
The method involves automatically generating a cell library by creating a continuous distribution of cell sizes and P/N ratios, including drive strength variants, topology variants, and buffer variants, to support efficient timing closure, using seed transistor networks and alternative transistor networks to derive a range of cell sizes and ratios that can cover target output capacitances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a cell library is designed with limited cell variants, then the library size and complexity are reduced, but timing closure efficiency deteriorates
Solution Approach 1:
The patent applies parameter changes by systematically varying key cell parameters including drive strength (multiple levels), P/N ratios (different combinations), and topology types (series-parallel configurations). This creates a comprehensive set of cell variants that improve timing closure efficiency without requiring excessive library complexity, as each parameter variation serves a specific timing optimization purpose.
Solution Approach 2:
The patent segments the cell library design into distinct categories based on functionality and timing characteristics. Cells are divided into different drive strength levels, P/N ratio groups, and topology types, allowing the design tool to selectively choose appropriate cell variants for specific timing requirements, thereby improving timing closure efficiency while maintaining manageable library complexity.
2Productivity
If a continuous spectrum of cell variants is generated, then timing closure efficiency is improved, but the cell library size and complexity increase
Solution Approach 1:
The patent systematically varies parameters such as drive strength (with multiple levels), P/N ratios (different combinations), and topology types to generate a continuous spectrum of cell variants. This approach improves timing closure efficiency by providing fine-grained control over cell characteristics while maintaining manageable complexity through structured parameter variation rather than arbitrary proliferation of cell types.
Solution Approach 2:
The patent creates universal cell templates that can serve multiple functions through parameter variation. A single cell topology can provide multiple drive strengths and P/N ratios, reducing the need for completely separate cell designs for each timing requirement. This multi-functionality approach generates a continuous spectrum of variants while controlling overall library complexity.
3Measurement precision
If multiple drive strength variants are included, then timing precision is improved, but the number of cell variants increases
Solution Approach 1:
The patent implements multiple drive strength variants by systematically varying the drive strength parameter across different cell instances. This provides improved timing precision by allowing selection of cells with drive strengths that precisely match the required timing specifications, while the structured approach to parameter variation prevents uncontrolled proliferation of cell variants.
Solution Approach 2:
The patent applies local quality by providing different drive strength variants only where timing precision requirements demand them. The design tool can selectively choose from multiple drive strength options for specific cells based on local timing requirements, rather than uniformly increasing complexity across the entire library. This localized approach improves timing precision without unnecessarily increasing the total number of cell variants.
Data Source
AI summary
A cell library is automatically designed. An emphasis of a design methodology is on automatic determination of the desired or needed cell sizes and variants. This method exploits different variants on drive strengths, P/N ratios, topology variants, internal buffering, and so forth. The method allows generating libraries that are more suitable for efficient timing closure.