High-Speed Transmitter Clock Calibration for Duty Cycle and Phase Skew
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Solution Overview
Problem
Conventional high-speed transmitters using 4T clocks face challenges with inaccurate phase correction, requiring both duty cycle and phase correction, which affects performance and power consumption.
Innovation Solution
A transmitter device with a clock calibrator circuit that performs iterative duty cycle and phase calibration of clock signals, using a reference clock signal and a fixed pattern of data signals to account for skew introduced by other components, ensuring accurate phase alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a 4T clock is used in a high speed transmitter, then power consumption is reduced compared to 2T clock, but both duty cycle correction and phase correction are required with inaccurate phase correction
Solution Approach 1:
The patent performs duty cycle calibration before phase calibration in a predetermined sequence. The duty cycle calibration adjusts the duty cycles of clock signals to be substantially equal before proceeding to phase calibration, which uses the calibrated clock signals as reference. This preliminary duty cycle adjustment ensures accurate phase measurement and correction without the confounding effect of duty cycle variations.
Solution Approach 2:
The patent employs an iterative calibration process where phase calibration is performed by comparing each clock signal to a reference clock signal, adjusting phase based on measured differences. The system continuously monitors and adjusts phase until the desired accuracy is achieved, using feedback from the comparison process to drive corrections.
2Device complexity
If clock signals are used directly for phase calibration, then calibration process is simplified, but skew introduced by other transmitter components is not accounted for
Solution Approach 1:
The patent introduces data signals as an intermediary medium for phase calibration. Instead of directly comparing clock signals, the system calibrates phase by comparing data signals that have traversed the same transmission path and components as the actual data. This intermediary approach allows the calibration process to account for skew introduced by transmitter components while maintaining reasonable complexity.
3Measurement precision
If iterative phase calibration is performed using clock signals as reference, then phase accuracy can be improved, but calibration time increases
Solution Approach 1:
The patent performs duty cycle calibration before phase calibration, preparing the clock signals in advance with equalized duty cycles. This preliminary action reduces the complexity and time required for subsequent phase calibration, as the iterative process starts from a better-initialised state where only phase differences need to be corrected, not duty cycle variations as well.
Solution Approach 2:
The patent changes the calibration parameters by using data signals instead of clock signals for phase measurement, and by calibrating in a predetermined sequence (duty cycle first, then phase). These parameter changes optimize the calibration process to achieve sufficient accuracy more quickly by focusing adjustments on the most critical parameters in the correct sequence.
Data Source
AI summary
A transmitter device having a calibrator circuit is disclosed. The calibrator circuit performs duty cycle calibration and phase calibration on a plurality of clock signals of the transmitter device. In one embodiment, the phase calibration is performed based on a comparison of the clock signals to a reference clock signal from the plurality of clock signals. In another embodiment, the calibrator circuit uses fixed patterns of data signals to perform phase calibration on the plurality of clock signals.