Shared Power Rail Architecture for Standard Cell Height Reduction
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Solution Overview
Problem
Conventional standard cell designs require a dedicated retention rail that increases cell height or occupies routing tracks, which is inefficient due to the rail carrying only a fraction of the current of primary power rails, and results in wastefulness as it is dedicated to just one row of cells.
Innovation Solution
Implementing a cell-based architecture where a first power rail is shared between rows, a second power rail is wider to carry more current, and a third power rail extends across the interior, allowing for reduced cell height and efficient current distribution by aligning power rails with routing tracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated retention rail is added to each cell row, then retention voltage can be supplied to all cells, but cell height increases or routing tracks are occupied
Solution Approach 1:
The patent merges the retention rail function with existing primary power rails by routing retention voltage through the same physical infrastructure used for VDD/VSS. Instead of adding separate dedicated retention rails, the system combines multiple voltage functions into shared rail structures, eliminating the need for additional height or routing resources.
Solution Approach 2:
The power rails are designed to serve multiple functions simultaneously - carrying both primary power (VDD/VSS) and retention voltage (VDDR/VSSR) through the same physical pathways. This multi-functionality allows retention voltage distribution without requiring dedicated retention-only rails, thus avoiding increased cell height.
2Reliability
If a dedicated retention rail is added to each cell row, then retention voltage can be supplied to all cells, but routing tracks are occupied
Solution Approach 1:
The patent combines retention voltage routing with existing primary power rail routing paths. By merging the retention voltage distribution function into the already-established VDD/VSS routing infrastructure, the design avoids occupying additional routing tracks while still providing retention power to all necessary cells.
Solution Approach 2:
The routing tracks are designed to carry multiple voltage types simultaneously or sequentially. The same physical routing infrastructure that carries primary power voltages is also used to distribute retention voltages, making the routing system universal and eliminating the need for dedicated retention voltage routes.
3Reliability
If a retention rail is dedicated to just one row of cells, then retention voltage is available, but it is wasteful because it carries only a fraction of the current of primary power rails
Solution Approach 1:
The patent merges retention voltage distribution with primary power distribution by using shared rail structures. This combination allows the same physical infrastructure to serve both high-current primary power needs and lower-current retention needs, optimizing resource utilization and avoiding the waste of dedicated underutilized retention rails.
Solution Approach 2:
The power rails are designed as universal structures that can handle varying current loads by serving multiple functions. The same rails that carry full-current primary power also carry retention voltage when needed, allowing the system to optimize for primary power capacity while still accommodating retention requirements without waste.
Data Source
AI summary
A cell-based architecture for an integrated circuit. A row of cell instances borders a first adjacent row of cell instances along a first boundary and a second adjacent row of cell instances along a second boundary. A first power rail (e.g., carrying an auxiliary voltage) extends along the first boundary. A second power rail (e.g., VSS) extends along the second boundary. The second power rail is wider than the first power rail. Additionally, a third power rail (e.g., VDD) extends across the interior of the second row of cells.