Auto-Routing Signal and Return Paths for PCB Impedance Control
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Solution Overview
Problem
Current circuit design software struggles to effectively route signal and return paths, often requiring multiple reference planes, which increases costs and complexity, and auto-routers fail to optimize the placement of signal return paths, leading to improper referencing and impedance mismatches in high-frequency digital circuits.
Innovation Solution
A computer program and methodology that auto-routes critical signal paths simultaneously with corresponding return paths, ensuring proper reference returns, and merges adjacent return paths to optimize the layout, reducing the need for multiple reference planes by placing return vias strategically and routing signal paths in adjacent channels or layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple reference planes are used to route signal paths, then signal integrity is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges adjacent return paths that share the same reference net to create contiguous reference plane areas. This consolidation reduces the total number of separate reference planes needed while maintaining proper signal referencing, thereby reducing device complexity and cost without compromising signal integrity.
Solution Approach 2:
The patent enables return paths to serve multiple functions: they provide reference planes for signal integrity while also being consolidatable into larger contiguous areas that reduce the overall number of reference planes required. This multi-functionality allows the same structural elements to address both signal integrity and complexity reduction.
2Adaptability or versatility
If return paths are routed separately from signal paths, then routing flexibility is improved, but manufacturing precision deteriorates
Solution Approach 1:
The patent performs preliminary action by determining the placement of return paths simultaneously with signal paths during the auto-routing process, rather than routing them separately afterward. This simultaneous placement ensures proper alignment and spacing from the beginning, maintaining manufacturing precision while preserving routing flexibility through the automated algorithm.
Solution Approach 2:
The auto-routing algorithm incorporates feedback mechanisms that monitor placement tolerance and adjust the routing of both signal and return paths accordingly. This feedback ensures that return paths are placed with appropriate precision relative to their corresponding signal paths while maintaining the flexibility needed for complex routing scenarios.
3Ease of operation
If auto-router routes only signal paths over pre-designated power planes, then ease of operation is improved, but manufacturing precision deteriorates
Solution Approach 1:
The patent extends the preliminary action principle by having the auto-router determine return path placement simultaneously with signal path routing, rather than relying on pre-designated power planes. This simultaneous determination maintains ease of automated operation while achieving precise reference return placement that adapts to the actual signal path routing decisions.
Solution Approach 2:
The patent introduces dynamics by making the return path routing adaptive and flexible rather than fixed to pre-designated power planes. The auto-routing algorithm dynamically determines optimal return path locations based on signal path placement and reference net requirements, maintaining ease of operation through automation while achieving superior manufacturing precision.
4Adaptability or versatility
If reference planes are split to route signals, then routing flexibility is improved, but signal integrity deteriorates
Solution Approach 1:
The patent merges adjacent return paths with the same reference net to create contiguous reference plane areas, preventing the splitting of reference planes that would compromise signal referencing. This merging maintains signal integrity by ensuring continuous reference planes while the auto-routing algorithm preserves routing flexibility by finding alternative paths when necessary.
Data Source
AI summary
An auto routing method and system provides optimized circuit routing while maintaining proper reference return paths for critical signals. Critical signal paths are auto-routed simultaneously with corresponding reference return paths, and the reference return paths can be merged into reference planes if they are adjacent to regions connected to the same reference net. The reference return paths may be in a plane adjacent to the signal path plane in the same channel, or the reference returns may be routed in adjacent channels in the same plane as the signal path. A check may be performed on endpoints of each critical signal path to determine whether a reference return via is present within a proximity tolerance of the signal path endpoints, and a reference return via placed if not.