Multi-Phase Clock Skew Calibration Using Duty Cycle Feedback
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Solution Overview
Problem
In high-speed data communication systems, clock signal skew between multi-phase clock signals leads to errors and reduced system performance, necessitating a simple and reliable calibration method to reduce these skews.
Innovation Solution
A clock signal skew calibration apparatus comprising a clock skew calibration circuit with multiple delay lines and control circuits to adjust delays in multi-phase clock signals, using frequency doublers, dividers, and logic gates to achieve calibrated clock signals through closed-loop control systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multi-phase clock signals are used for high-speed data communication, then data transmission speed is improved, but clock signal skew increases causing errors and reduced system performance
Solution Approach 1:
The patent implements a feedback mechanism where the skew calibration circuit continuously monitors clock signal skew through duty cycle detection and adjusts delay lines accordingly. The frequency divider generates a signal whose duty cycle reflects the skew condition, which is then fed back to control the delay line adjustment, creating a closed-loop system that automatically corrects skew while maintaining high-speed operation
Solution Approach 2:
The patent changes the delay parameter of clock signals dynamically by adjusting the delay line settings based on detected skew conditions. The skew calibration circuit modifies the propagation delay of individual clock phases to equalize their arrival times, thereby correcting skew without reducing the overall clock frequency and maintaining high data transmission speed
2Reliability
If skew calibration circuits are added to reduce clock signal skew, then system performance is improved, but device complexity increases
Solution Approach 1:
The skew calibration circuit is designed to be universally applicable to multi-phase clock systems. The same circuit topology can calibrate any number of clock phases by simply adding corresponding delay lines and control paths. The frequency divider and duty cycle detection mechanism serve multiple calibration functions simultaneously, reducing the need for separate calibration circuits for each clock phase
Solution Approach 2:
The patent introduces an intermediary frequency divider that converts the complex skew measurement problem into a simpler duty cycle detection task. Instead of directly measuring and comparing multiple clock phases, the frequency divider generates a single signal whose duty cycle encodes the skew information, which can then be easily detected and used to control delay line adjustments
Data Source
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AI summary
An apparatus includes a clock skew calibration circuit configured to be coupled to a multi-phase clock generator through a plurality of delay lines, wherein a first clock skew calibration unit comprises a frequency doubler configured to receive a plurality of multi-phase clock signals and generate a clock signal based on the plurality of multi-phase clock signals, a frequency divider configured to receive the clock signal and generate a reduced frequency signal based on the clock signal, and a delay line control circuit configured to compare the duty cycle of the reduced frequency signal with a predetermined duty cycle, and generate a first control signal to adjust the skew of the first multi-phase clock signal through adjusting a first delay applied to the first multi-phase clock signal until a calibrated signal of the first multi-phase clock signal is achieved.