Duty Cycle Calibration Circuit With PLL Feedback Stability
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Solution Overview
Problem
The stability of the duty cycle in duty cycle calibration circuits is compromised by external interference, affecting the accuracy of the calibration clock signal and the quality of wireless communication signals.
Innovation Solution
A duty cycle calibration circuit comprising a duty cycle calibration cell, delay matching cell, phase-locked loop cell, and calibration control cell, which perform duty cycle calibration, delay matching, phase-locked processing, and sampling to align and adjust the duty cycle of the calibration clock signal to a target value, overcoming variations due to process, voltage, and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If duty cycle calibration is performed using conventional methods, then the duty cycle can be adjusted, but the stability is compromised by external interference affecting accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the calibrated clock signal is fed back through a phase-locked loop to continuously monitor and adjust the duty cycle. The PFD compares the phase of the feedback signal with the reference signal, and the D-type flip-flop samples the calibration clock signal to generate calibration control signals that adjust the duty cycle, forming a closed-loop feedback system that maintains stability despite external interference
Solution Approach 2:
The patent performs preliminary delay matching before the main calibration process. The delay matching cell pre-adjusts the timing relationships between signals to ensure that when calibration begins, the signals are already in optimal alignment. This preliminary action reduces the calibration burden and improves overall stability by establishing correct timing relationships in advance
2Measurement precision
If clock multiplier technology is used to increase reference clock frequency, then phase noise performance improves, but duty cycle stability becomes more critical
Solution Approach 1:
The feedback mechanism continuously monitors the duty cycle of the multiplied clock signal and makes real-time adjustments. The phase-locked loop detects any duty cycle deviations in the high-frequency clock signal and generates appropriate calibration control signals to correct them, ensuring that the improved phase noise performance is maintained with stable duty cycle
Solution Approach 2:
The patent employs dynamic adjustment mechanisms where the duty cycle calibration cell can adaptively modify the duty cycle based on real-time conditions. The system transitions from static duty cycle settings to dynamic adjustment, allowing the duty cycle to be optimized continuously according to the operating conditions of the clock multiplier circuit
3Adaptability or versatility
If multiple calibration control signals are generated for different duty cycle values, then calibration flexibility increases, but system complexity increases
Solution Approach 1:
The patent replaces multiple static calibration control signals with a single dynamic control mechanism. Instead of having separate control signals for different duty cycle values, the system uses a D-type flip-flop and phase-locked loop to dynamically generate the appropriate calibration control signal based on real-time phase and duty cycle measurements, reducing complexity while maintaining flexibility
Solution Approach 2:
The calibration system is designed to self-adjust and self-calibrate without requiring external intervention for each duty cycle value. The phase-locked loop and sampling circuitry automatically detect duty cycle deviations and generate the necessary calibration control signals autonomously, eliminating the need for complex external control signal management
Data Source
AI summary
Provided a duty cycle calibration circuit, method and clock multiplier circuit, wherein the duty cycle calibration circuit generates a delay-matched clock signal that is aligned with the first edge of the calibration clock signal and has the same duty cycle as the calibration clock signal through a delay matching cell, and generates a feedback clock signal that is aligned with the first edge of the calibration clock signal and has the target duty cycle through a phase-locked loop cell when the phase-locked loop cell is in the locked state, thereby performing sampling processing on the delay-matched clock signal using the feedback clock signal through the calibration control cell when the phase-locked loop cell is in the locked state, can acquire a sampled signal is used to instruct the relationship between the duty cycle of the calibration clock signal and the target duty cycle.