4-Phase Clock Skew Calibration via Delay-Line Duty Cycle Control
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Solution Overview
Problem
In high-frequency data communication systems, clock signal skews in multi-phase clock signals lead to errors in analog-to-digital conversion and reduced system performance, necessitating a simple and reliable calibration method.
Innovation Solution
A clock signal skew calibration apparatus comprising a clock skew calibration circuit coupled to a multi-phase clock generator through delay lines, utilizing a frequency doubler, frequency divider, and delay line control circuit to adjust delays and calibrate the skew of 4-phase clock signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multi-phase clock signals are used in high-frequency data communication systems, then data transmission speed is improved, but clock signal skew increases causing errors in analog-to-digital conversion and reduced system performance
Solution Approach 1:
The patent implements a feedback mechanism where the duty cycle of the reduced frequency signal is continuously monitored and compared against a predetermined duty cycle. The delay line control circuit adjusts the delay applied to multi-phase clock signals based on this comparison, creating a closed-loop feedback system that automatically corrects clock skew to maintain reliable system performance at high transmission speeds.
Solution Approach 2:
The patent changes the delay parameter applied to multi-phase clock signals dynamically. By adjusting the delay through the delay line control circuit based on duty cycle measurements, the system optimizes clock signal timing parameters to eliminate skew while maintaining high-frequency operation, thus resolving the contradiction between speed and reliability.
2Measurement precision
If clock skew calibration is performed to reduce errors in analog-to-digital conversion, then measurement precision is improved, but device complexity increases due to additional calibration circuits
Solution Approach 1:
The frequency doubler and frequency divider circuits serve multiple functions: they not only generate the reduced frequency signal for duty cycle measurement but also provide clock signals for the delay lines and calibration processes. This multi-functionality reduces the need for separate dedicated calibration circuits, thereby limiting the increase in device complexity while achieving improved timing accuracy.
Solution Approach 2:
The reduced frequency signal acts as an intermediary that carries skew information in its duty cycle. By measuring the duty cycle of this intermediate signal rather than directly measuring clock skew, the system achieves precise timing measurement through a simplified indirect measurement approach, balancing measurement precision with circuit complexity.
3Manufacturing precision
If delay lines are used to adjust clock signal timing, then clock skew is reduced, but device complexity increases due to additional delay line control circuits
Solution Approach 1:
The patent merges the delay line control function with the existing frequency doubling and division circuits. The same control circuitry that generates frequencies for the delay lines also performs the duty cycle comparison and skew correction decisions. This merging of functions achieves precise clock signal timing adjustment while minimizing the addition of separate control circuits, thus limiting complexity increase.
Data Source
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.