Multiphase Receiver Clock Buffering for Duty Cycle and Skew Control
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Solution Overview
Problem
Existing receiver clock systems in chip-to-chip communication suffer from undesirable duty cycle variations and skew due to variations among ring oscillator elements, leading to degraded signal detection quality.
Innovation Solution
A configurable clock buffer chain is used to adjust clock duty cycle and delay by modifying the rise and fall times of signals, combined with a measurement subsystem to directly measure clock duty cycle and inter-phase skew, providing clean, accurately timed multiphase clock signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ring oscillator elements are used to generate multiphase clock signals, then clock signal generation is achieved, but duty cycle variations and skew occur due to element variations
Solution Approach 1:
The patent implements feedback mechanisms through phase detectors that continuously monitor the phase relationships between multiphase clock signals and adjust the ring oscillator elements accordingly. This closed-loop control compensates for duty cycle variations and skew caused by manufacturing variations in the ring oscillator elements, thereby maintaining reliable signal detection quality.
Solution Approach 2:
The patent dynamically adjusts parameters of the ring oscillator elements, specifically the delay values of individual delay elements, to compensate for manufacturing variations. By changing these parameters through calibration and adjustment mechanisms, the system corrects duty cycle inaccuracies and phase skew while maintaining the desired multiphase clock signal generation.
2Productivity
If multiple local clocks with particular phase relationships are generated, then parallel processing capability is improved, but clock skew and phase accuracy deteriorate
Solution Approach 1:
The patent divides the clock generation system into multiple independently controllable ring oscillator elements and delay elements. Each element can be individually calibrated and adjusted to achieve precise phase relationships. This segmentation allows parallel processing capability while maintaining accurate phase control through independent optimization of each segment.
Solution Approach 2:
The patent implements dynamic adjustment mechanisms that allow the phase relationships between multiple local clocks to be continuously optimized. The system can adaptively adjust delay values and phase offsets in real-time to maintain accurate phase relationships even as operating conditions change, thereby preserving both parallel processing capability and phase accuracy.
3Manufacturing precision
If duty cycle and delay adjustment is implemented by modifying rise and fall times, then clock signal accuracy is improved, but circuit complexity increases
Solution Approach 1:
The patent designs the delay elements and buffer stages to serve multiple functions: they provide signal buffering, delay adjustment, and duty cycle correction simultaneously. By making these components multi-functional, the patent achieves accurate clock signal generation without proportionally increasing circuit complexity, as the same structural elements perform multiple corrective functions.
Data Source
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AI summary
Methods and systems are described for generating, at a plurality of delay stages of a local oscillator, a plurality of phases of a local oscillator signal, generating a loop error signal based on a comparison of one or more phases of the local oscillator signal to one or more phases of a received reference clock, generating a plurality of phase-specific quadrature error signals, each phase-specific quadrature error signal associated with a respective phase of the plurality of phases of the local oscillator signal, each phase-specific quadrature error signal based on a comparison of the respective phase to two or more other phases of the local oscillator signal, and adjusting each delay stage according to a corresponding phase-specific quadrature error signal of the plurality of phase-specific quadrature error signals and the loop error signal.