Duty Cycle Detector Offset Cancellation in Clock Calibration Circuits
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Solution Overview
Problem
Duty cycle distortion in clock signals used in electrical circuit devices leads to timing issues and unreliable performance, especially at high input/output speeds, and existing duty cycle detector calibration methods struggle with offset errors, making it difficult to correct distortions accurately.
Innovation Solution
The implementation of a duty cycle calibration circuit that includes a duty cycle detector and adjuster, capable of automatically canceling offset errors without recalibration, by performing initial and flipped searches to determine a code value that corrects duty cycle distortions, thereby ensuring accurate adjustment of clock signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If duty cycle detector calibration is performed to determine trim value, then duty cycle distortion correction is improved, but device complexity and recalibration requirements increase
Solution Approach 1:
The duty cycle detector circuit performs self-calibration by automatically detecting and correcting its own offset errors through the flipped search mode, eliminating the need for external calibration equipment and manual trim value determination. The circuit uses its own resources (clock signals, charge-discharge circuits, comparator) to perform the calibration function.
Solution Approach 2:
The calibration process is performed in advance during initialization or setup phase, determining the trim value before actual duty cycle correction operations begin. This preliminary calibration ensures accurate correction is available when needed without adding complexity to the operational path.
2Ease of operation
If DCD offset is not canceled, then device operation is simplified, but duty cycle distortion correction accuracy deteriorates
Solution Approach 1:
The circuit uses feedback through the comparator to detect the output state and automatically adjust the trim value accordingly. The comparator monitors whether the duty cycle detector output is high or low and feeds this information back to the calibration logic, which adjusts the trim value to achieve the desired 50% duty cycle point.
Solution Approach 2:
The trim value is made dynamic and adjustable rather than fixed, allowing the circuit to adapt to offset errors automatically. The calibration logic can modify the trim value in real-time based on the detected offset condition, making the system dynamically compensating for errors.
3Measurement precision
If conventional calibration method is used, then initial offset correction is achieved, but frequent recalibration is required due to offset drift
Solution Approach 1:
The circuit continuously monitors its own offset condition through the comparator and automatically performs recalibration when needed without external intervention. This self-service capability reduces the need for manual recalibration and maintains accuracy over time and temperature variations.
Solution Approach 2:
The continuous feedback mechanism through the comparator allows the circuit to detect offset drift in real-time and trigger recalibration automatically, maintaining measurement precision without requiring frequent external recalibration events.
Data Source
AI summary
Several embodiments of electrical circuit devices and systems with a duty cycle correction apparatus that includes a duty cycle adjustment circuit that is configured to adjust a duty cycle of the input clock signal based on an averaged code value. The duty cycle correction apparatus includes a duty cycle detector circuit that receives first and second clock signals from a clock distribution network. The duty cycle detector is configured to output a duty cycle status signal that indicates whether the first clock signal is above or below a 50% duty cycle based on a comparison of the first clock signal to the second clock signal. The duty cycle correction apparatus also includes a counter logic circuit configured to determine the average code value, and the counter logic circuit automatically cancels an offset of the duty cycle detector when determining the averaged code value.