Logic Cell Placement for Uniform Voltage Drop
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Solution Overview
Problem
Existing integrated circuit design methods face challenges in accurately managing voltage drops across logic cells, leading to signal timing degradation and potential device failure, particularly due to inadequate initial voltage drop analysis and inefficient logic cell placement, which increases design cycle time and requires costly iterations.
Innovation Solution
A method for determining the initial placement of logic cells in integrated circuits that involves filling a defined area with a maximum number of uniformly spaced cells, checking voltage drop limits, and adjusting cell density to meet requirements, while considering the switching factor and cross-talk, ensuring uniform voltage drop characteristics across the area and power distribution rails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If logic cells are clustered together to meet timing requirements and reduce signal attenuation, then signal integrity is improved, but voltage drop increases causing timing degradation and potential failure
Solution Approach 1:
The patent applies local quality by creating distinct placement regions with different logic cell densities. High-density regions are placed where voltage drop is less critical, while low-density regions are positioned near signal ports where maintaining voltage integrity is essential. This spatial differentiation of cell density optimizes both signal integrity and voltage drop characteristics locally across the circuit.
Solution Approach 2:
The patent performs preliminary voltage drop analysis during the placement phase to predict and prevent voltage drop issues before routing is completed. By analyzing voltage drops early and using this information to guide logic cell placement, the design avoids timing degradation and functional failure that would require costly iterations later in the design cycle.
2Reliability
If traditional iterative placement methods are used to fix voltage drop issues, then voltage drop requirements are met, but design cycle time increases significantly
Solution Approach 1:
The patent performs voltage drop analysis and logic cell placement simultaneously in a single pass, rather than iteratively. By integrating the placement algorithm with voltage drop prediction, the system determines optimal placements that satisfy voltage requirements from the outset, eliminating multiple design cycles and significantly reducing time to tape-out.
Solution Approach 2:
The patent incorporates voltage drop information as feedback during the placement process. The system calculates voltage drops for candidate placements and uses this feedback to guide the placement algorithm, selecting configurations that meet voltage requirements without requiring subsequent iterative corrections.
3Productivity
If maximum number of logic cells are placed in an area to maximize functionality, then area utilization is improved, but voltage drop exceeds acceptable limits
Solution Approach 1:
The patent divides the circuit area into multiple placement regions with different logic cell density characteristics. Each region is optimized independently, allowing maximum cell density in regions where voltage drop is not critical while maintaining lower density near signal ports where voltage integrity is essential, thus balancing area utilization with voltage drop constraints.
Solution Approach 2:
The patent segments the logic cell placement into distinct regions based on their electrical characteristics and proximity to signal ports. This segmentation allows the system to place maximum cells in appropriate regions while preventing excessive cell density in regions that would cause unacceptable voltage drops, optimizing the trade-off between functionality and electrical integrity.
Data Source
AI summary
A method that determines the maximum number of logic cells that can be placed in a predetermined area on the base of an integrated circuit, and meet a voltage drop requirement. The method iteratively changes the logic cell spacing until the voltage drop requirement is made. This is done prior to the placement and extraction design phases as was done in previous methods. The predetermined area may be extrapolated across the base of the integrated circuit and meet the voltage drop requirements without the need to change the power grid, or to redo the placement and extraction phases. An integrated circuit designed according to the method, and an integrated circuit design system for using the method is also disclosed.