Optical Clock Path for Integrated Circuit Skew Control
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Solution Overview
Problem
High-performance circuits face challenges in achieving equal clocking due to clock skew and jitter, which are difficult to reduce and result in significant power consumption during clock signal distribution.
Innovation Solution
An integrated circuit with an optical clock path that dynamically adjusts skew values and gates clock signals based on activity, using techniques such as modifying the index of refraction and evanescent coupling with a ring resonator, to optimize clock signal distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electrical clock distribution is used, then circuit elements can be clocked, but clock skew and jitter occur making equal clocking difficult to achieve
Solution Approach 1:
The patent replaces the electrical clock distribution system with an optical system. Electrical clock signals are converted to optical signals using electro-optic modulators, transmitted through optical waveguides, and converted back to electrical signals using photodetectors. This substitution eliminates the electrical interference and signal degradation that cause clock skew and jitter in conventional systems, achieving superior clocking precision and reliability.
Solution Approach 2:
The patent introduces optical signals as an intermediary between the clock source and circuit elements. Instead of directly distributing electrical signals through wires that suffer from impedance mismatches and crosstalk, the system uses optical waveguides as an intermediary medium to transmit clock information, thereby eliminating the harmful electrical interactions that cause timing variations.
2Productivity
If clock signals are distributed to all circuit elements, then all elements can be synchronized, but significant power consumption occurs
Solution Approach 1:
The patent implements periodic action by using optical clocks that can be selectively activated. Instead of continuously distributing clock signals to all circuit elements, the system can periodically enable clock distribution only when needed, reducing power consumption while maintaining synchronization capability when active.
Solution Approach 2:
The patent applies local quality by enabling selective clock distribution to specific circuit elements or regions. Through optical switching and gating mechanisms, the system can direct clock signals only to active or required portions of the circuit, rather than uniformly distributing power to all elements, thereby reducing overall power consumption while maintaining productivity where needed.
3Adaptability or versatility
If clock paths are made longer to reach all elements, then more elements can be clocked, but clock skew increases
Solution Approach 1:
The patent transitions from two-dimensional electrical signal propagation to three-dimensional optical signal transmission through waveguides. This dimensional change allows for more flexible routing and shorter effective path lengths while reaching distant circuit elements, as optical signals can be directed through controlled paths that minimize skew while maximizing coverage.
Solution Approach 2:
The patent utilizes parameter changes in the optical domain to control signal propagation. By adjusting optical parameters such as wavelength, phase, and amplitude through modulators and switches, the system can dynamically optimize clock distribution to accommodate varying circuit topologies and path lengths, maintaining timing precision across extended circuits without being constrained by fixed electrical propagation characteristics.
4Ease of manufacture
If existing clock distribution geometries (H-trees, grids, spines) are used, then clock signals can be distributed, but clock skew and jitter cannot be eliminated
Solution Approach 1:
The patent replaces conventional electrical clock distribution geometries with an optical transmission system. By using optical waveguides instead of electrical interconnects, the system eliminates the manufacturing and layout constraints that cause clock skew in traditional approaches, achieving superior timing precision while maintaining ease of implementation through standardized optical components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces clock skew and jitter, lowers power consumption, and enables precise control over clock phases, facilitating efficient distribution of clock signals while accommodating varying logical path delays.
Implementation Method 1
the optical clock path is configured to set the skew value by modifying an index of refraction in the optical clock path
Implementation Method 2
the optical clock path is configured to selectively gate distribution of the optical signal to the latch based on activity of the latch, where the selective gating is performed optically
Data Source
AI summary
Embodiments of an integrated circuit are described. This integrated circuit includes: a clock-generator circuit configured to provide a clock signal; an optical clock path coupled to the clock-generator circuit; and a latch coupled to the optical clock path. This optical clock path is configured to distribute an optical signal corresponding to the clock signal. Furthermore, the optical clock path is configured to optically set a skew value for the optical signal, and is configured to selectively gate distribution of the optical signal to the latch based on activity of the latch. Note that the selective gating is performed optically.