Multi-Phase Clock Skew Calibration Using Delay Line 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
1Productivity
If the clock rate of the data communication system is increased to achieve higher speeds, then productivity is improved, but clock signal skew increases causing errors in analog-to-digital conversion and reduced system reliability
Solution Approach 1:
The patent applies preliminary action by performing skew calibration on multi-phase clock signals before they are used for data communication. The calibration circuit pre-adjusts the phase alignment of clock signals from the clock generator, ensuring that when high-speed data transmission occurs, the clock signals are already properly synchronized, preventing conversion errors that would otherwise occur at high clock rates
2Device complexity
If a ring oscillator is used to generate multi-phase clock signals, then device complexity is reduced, but clock signal skew increases at higher frequencies
Solution Approach 1:
The patent introduces an intermediary calibration circuit between the ring oscillator and the data communication system. This calibration circuit acts as a mediator that receives the multi-phase clock signals from the simple ring oscillator and adjusts their phase alignment, thereby maintaining the simplicity of the clock generation structure while eliminating the timing accuracy problems that arise at high frequencies
3Adaptability or versatility
If multi-phase clock signals are used for phase interpolation in CDR circuits, then adaptability is improved for high-speed communication, but clock skew calibration becomes more difficult
Solution Approach 1:
The patent implements self-service by designing a calibration circuit that automatically detects and corrects skew in multi-phase clock signals without requiring complex external measurement equipment or manual adjustment. The calibration circuit uses the clock signals themselves to generate calibration information and autonomously adjusts the phase alignment, making the process simple despite the sophisticated CDR functionality being supported
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 of the clock skew calibration circuit comprises a frequency doubler configured to receive a plurality of multi-phase clock signals and generate a clock signal, a frequency divider configured to receive the clock signal and generate a reduced frequency signal indicative of a skew of a first multi-phase clock signal, and a delay line control circuit configured to adjust the skew of the first multi-phase clock signal by comparing the reduced frequency signal with a predetermined duty cycle, and generating a control signal to modify a delay applied to the first multi-phase clock signal.