Voltage-Controlled Delay Line Duty Cycle Correction for Clock Jitter
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Solution Overview
Problem
Existing systems face challenges in accurately correcting duty cycle errors in clock signals, which can lead to increased jitter and distortion, particularly in high-speed digital computing and communication systems.
Innovation Solution
A duty cycle correction circuit that combines analog and digital control signals to adjust the duty cycle of an output clock signal, utilizing a voltage-controlled delay line (VCDL) with a low-pass filter, amplifier, and reset logic to generate a final reset signal, ensuring a desired duty cycle, such as 50%, is achieved by selecting a delay range and adjusting the delay amount based on digital and analog command signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage controlled delay line is used to correct duty cycle error, then the duty cycle precision is improved, but the device complexity increases due to the combination of analog and digital control circuits
Solution Approach 1:
The patent merges analog control (via the low-pass filter and amplifier generating analog voltage) with digital control (via the digital command signal selecting delay ranges) within a unified voltage-controlled delay line structure. This combination allows the system to achieve high duty cycle precision by leveraging both analog fine-tuning capability and digital coarse-adjustment capability, while the merged architecture avoids the need for completely separate analog and digital correction systems.
Solution Approach 2:
The delay line is segmented into multiple controllable stages, where the digital command signal selects specific delay ranges by activating particular segments, and the analog voltage provides fine-tuning within each segment. This segmentation allows the complex correction task to be divided into manageable discrete steps (digital selection) plus continuous adjustment (analog tuning), improving precision without requiring a monolithic complex circuit.
2Measurement precision
If analog and digital control signals are combined to adjust duty cycle, then the duty cycle correction accuracy is improved, but the ease of operation deteriorates due to dual control inputs
Solution Approach 1:
The system employs a feedback mechanism where the low-pass filter continuously monitors the output clock signal and automatically generates the appropriate analog control voltage based on detected duty cycle deviations. This self-service approach eliminates the need for manual analog adjustment, as the system automatically generates the fine-tuning voltage in response to measured errors, maintaining high accuracy while simplifying operation.
Solution Approach 2:
The low-pass filter provides continuous feedback about the duty cycle error to the analog control path, creating a closed-loop system that automatically adjusts the analog voltage to correct deviations. This feedback mechanism allows the system to maintain high correction accuracy automatically, reducing the operational burden on the user while preserving precision through continuous error monitoring and correction.
Data Source
AI summary
Electrical circuits and associated methods relate to duty cycle correction having a voltage controlled delay line VCDL controlled by an analog voltage and a digital command signal to generate a VCDLout signal. In an illustrative example, the analog voltage may be generated by an analog circuit, the analog circuit may include a reference voltage, a low-pass filter, an amplifier and a loop filter. In an illustrative example, the analog circuit may be controlled by an analog command signal. The analog command signal may be programmable applied on the analog circuit to produce the analog voltage. The digital command signal may be programmable to select desired delay band in the VCDL. The analog voltage and the digital command signal may be applied to the VCDL together to obtain a desired duty cycle.