Differential Clock Transmission Circuit for Duty Cycle Accuracy
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Solution Overview
Problem
The increasing frequency of clock signals in semiconductor devices leads to difficulties in accurately supplying the clock signal due to potential delays and duty cycle errors, as well as significant leakage current issues.
Innovation Solution
A clock transmission circuit is designed with additional drivers and inverters to align the transition angles of differential clock signals, minimizing duty cycle errors and leakage current by using cross-coupled transistors with a stack structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the frequency of clock signals is increased to improve operating speed, then productivity is improved, but manufacturing precision deteriorates due to duty cycle errors and timing delays
Solution Approach 1:
The clock transmission path is segmented into multiple inverters (first inverter, second inverter, third inverter) with dedicated additional drivers. Each inverter stage is independently controlled to precisely manage signal transitions and minimize duty cycle errors at high frequencies
Solution Approach 2:
The patent changes the driving parameters by introducing additional drivers that selectively control the switching timing of each inverter stage. This allows dynamic adjustment of signal transition characteristics to maintain duty cycle accuracy despite increased operating frequency
2Device complexity
If conventional inverters are used to transmit clock signals, then device complexity is minimized, but loss of energy increases due to significant leakage current
Solution Approach 1:
Additional driver circuits are introduced as intermediary elements between the clock signal source and the inverter stages. These drivers act as mediators that control the switching behavior to minimize leakage current while maintaining signal integrity
Solution Approach 2:
The patent modifies the operational parameters of the inverter stages by adding controlled driving signals. This changes the switching characteristics to reduce off-state leakage current without requiring a complete redesign of the inverter structure
3Manufacturing precision
If additional drivers and cross-coupled transistors are added to minimize duty cycle errors, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The clock transmission circuit is divided into discrete inverter stages (first, second, third inverters) with individual additional drivers for each stage. This segmentation allows precise control of duty cycle at each stage while maintaining modular architecture that limits overall complexity
Solution Approach 2:
The additional drivers serve multiple functions: they control the switching timing of inverters, minimize duty cycle errors, and reduce leakage current. This multi-functionality justifies the added complexity by achieving multiple performance improvements simultaneously
4Productivity
If clock signal frequency is increased, then productivity is improved, but reliability deteriorates due to timing delays and duty cycle errors
Solution Approach 1:
Additional drivers are positioned upstream in the signal path to preemptively control the switching behavior of each inverter stage. This preliminary action ensures that signal transitions are precisely timed before potential errors can accumulate, maintaining reliability at high frequencies
Solution Approach 2:
The cross-coupled transistor configuration creates a feedback mechanism that monitors and corrects signal transitions. This feedback ensures that duty cycle errors are minimized and timing accuracy is maintained throughout the transmission path
Data Source
AI summary
A clock transmission circuit including a first inverter configured to inversion-drive a first transmission node in response to a first clock signal, among differential clock signals that are loaded onto a first reception node, a second inverter configured to inversion-drive a second transmission node in response to a second clock signal, among the differential clock signals that are loaded onto a second reception node, a first additional driver configured to additionally drive the first transmission node in response to the second clock signal that is loaded onto the second reception node, and a second additional driver configured to additionally drive the second transmission node in response to the first clock signal that is loaded onto the first reception node.