Hybrid Clock Network Reducing Skew via Ring-Tree Placement
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Solution Overview
Problem
Clock skew issues in integrated circuit chips arise due to unequal propagation delays caused by process variations, voltage drops, and temperature gradients, which existing H-tree clock distribution networks struggle to fully address, leading to both systematic and random skew.
Innovation Solution
A hybrid clock distribution network with a ring-shaped semi-grid structure, featuring concentric inner and outer bands and a clock distribution tree with signal drivers positioned to minimize IR drops and temperature gradients, ensuring all drivers experience similar conditions, thus reducing skew.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an H-tree clock distribution network is used to equalize propagation distances, then systematic clock skew is reduced, but random clock skew due to IR drop and temperature gradients remains significant
Solution Approach 1:
The patent positions signal drivers in specific locations within a ring-shaped semi-grid clock network to create locally optimized zones. Drivers are strategically placed at intersections of clock tree branches and ring bands, ensuring each local region experiences balanced IR drop and temperature gradients, thereby reducing random clock skew while maintaining systematic skew control
Solution Approach 2:
The ring-shaped semi-grid structure with concentric inner and outer bands creates equipotential regions that equalize voltage distribution across the chip. By positioning drivers within these balanced potential zones and using the ring structure to distribute power evenly, the network minimizes IR drop variations and temperature gradients, reducing random clock skew to match the precision of systematic skew control
2Measurement precision
If more signal drivers and stages are added to the clock distribution network, then clock skew is better controlled, but power consumption increases and tuning complexity increases
Solution Approach 1:
The ring-shaped semi-grid structure serves multiple functions simultaneously: it distributes clock signals, provides power delivery paths, and creates balanced potential zones. This multi-functional design reduces the need for separate power distribution networks and additional buffering stages, lowering overall device complexity while maintaining precise clock skew control
Solution Approach 2:
The patent merges the clock distribution function with the power distribution function by integrating the ring-shaped clock network with power delivery paths. This combination allows the same structural elements to serve dual purposes, reducing the total number of components and stages needed compared to separate clock and power distribution networks
3Reliability
If signal drivers are positioned to minimize IR drops and temperature gradients, then random clock skew is reduced, but the network complexity increases
Solution Approach 1:
The patent employs asymmetric positioning of signal drivers within the symmetric ring structure, placing drivers at specific intersections where clock tree branches meet ring bands. This asymmetric placement optimizes local IR drop and temperature gradient conditions without requiring complex asymmetric network architecture, maintaining structural simplicity while achieving reliable clock signal distribution
Data Source
AI summary
Some of the embodiments of the present invention provide an integrated circuit device including a clock distribution network, the clock distribution network comprising an inner band, an outer band, and a clock distribution tree including a plurality of stages, each stage including a plurality of signal drivers, wherein all signal drivers of at least one stage of the clock distribution tree are placed in an area between the inner band and the outer band. Other embodiments are also described and claimed.