Hierarchical Clock Tree Layout for Balanced Signal Latency
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Solution Overview
Problem
In synchronous circuits, clock signals often reach input/output ports at different latencies due to unequal distances from clock generators, leading to latency imbalances, especially in core circuits without internal clock trees.
Innovation Solution
A global hierarchical clock tree architecture is implemented, featuring clock generator modules at strategic locations and multiplexers to distribute clock signals evenly, ensuring equal latencies across all ports through a balanced, low skew clock network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If clock signals are distributed from a single clock generator to all input/output ports, then the circuit structure is simplified, but latency imbalances occur due to unequal distances from the clock generator to different ports
Solution Approach 1:
The patent divides the clock distribution network into hierarchical segments: global clock generators at chip corners feed regional clock buffers, which then distribute to local clock buffers, and finally to individual input/output ports. This segmentation allows each segment to be optimized independently, achieving both structural simplicity and timing precision through modular organization.
Solution Approach 2:
The patent implements local quality by placing clock buffers at strategic locations throughout the chip rather than using a uniform distribution. Each regional and local clock buffer is positioned to optimize timing for its specific region, allowing different parts of the chip to have customized clock distribution paths that compensate for varying distances and routing complexities.
2Manufacturing precision
If clock generators are placed at all four corners of the core circuit, then latency balance is improved, but the device complexity increases
Solution Approach 1:
The patent segments the clock generation function across four corner locations, with each clock generator responsible for serving its adjacent regions. This segmentation distributes the complexity of achieving timing balance across multiple simple, identical modules rather than requiring one complex centralized system, making the overall design more manageable and scalable.
Solution Approach 2:
The patent achieves equipotentiality by strategically positioning clock generators at all four corners of the core circuit, ensuring that maximum distance from any input/output port to its nearest clock generator is minimized and balanced. This creates equivalent timing potential across all regions of the chip, allowing uniform performance regardless of location.
3Manufacturing precision
If a hierarchical clock tree with multiple buffer stages is implemented, then latency balance across ports is achieved, but the number of components and circuit complexity increases
Solution Approach 1:
The hierarchical clock tree segments the distribution function into global and local clock buffers, where global buffers handle long-distance distribution from corner generators and local buffers handle short-distance distribution to individual ports. This segmentation reduces the total number of components needed compared to a flat architecture, as each buffer stage operates over optimized distance ranges.
Solution Approach 2:
The patent introduces a hierarchical dimension to the clock distribution architecture, organizing buffers into multiple levels (global and local) rather than a single flat level. This dimensional organization allows efficient fan-out patterns where each buffer serves a specific hierarchical level, reducing overall component count while maintaining timing balance.
Data Source
AI summary
Methods, systems, and circuits for forming and operating a global hierarchical clock tree are described. The global hierarchical clock tree may comprise a clock circuit that operates to provide clock signals to a core circuit surrounded by the clock circuit. The clock circuit may include two or more first and second clock generator modules to generate a first and a second set of clock signals, respectively. The first and second clock modules may be located so that the first set of clock signals experience approximately equal first latencies and the second set of clock signals experience approximately equal second latencies. Additional methods, systems, and circuits are disclosed.