CDR Phase Control Using Coarse-Fine Clock Adjustment
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Solution Overview
Problem
High-speed communication systems face challenges in implementing clock and data recovery (CDR) circuits that require wider phase adjustment ranges and operate at higher speeds, making it difficult to maintain accurate data reading and prevent spikes in clock signals.
Innovation Solution
A CDR device comprising data analysis, loop filter, phase rotator, multiplexer, and phase interpolator circuitries that analyze input data, update adjustment signals, and adjust clock signals step-by-step to achieve precise phase control, allowing the phase rotator to operate at lower frequencies and generate higher-frequency clock signals, thereby reducing circuit complexity and preventing spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the CDR circuit operates at higher speeds to meet bandwidth requirements, then the operating speed is improved, but the implementation difficulty of internal circuits increases
Solution Approach 1:
The phase adjustment function is segmented into two independent stages: a coarse adjustment stage using a phase rotator and a fine adjustment stage using a phase interpolator. This segmentation allows each stage to operate at optimized frequencies, with the phase rotator working at lower frequencies to reduce implementation difficulty while the phase interpolator handles high-speed fine adjustments.
Solution Approach 2:
A low-frequency phase rotator is introduced as an intermediary component between the loop filter and the high-frequency phase interpolator. The phase rotator pre-adjusts the phase at low frequency, reducing the burden on the high-speed phase interpolator and simplifying the overall circuit implementation.
2Adaptability or versatility
If the phase adjustment range is widened to meet current requirements, then the phase control range is improved, but the circuit implementation becomes more difficult
Solution Approach 1:
The wide phase adjustment range is achieved by segmenting the adjustment into coarse and fine components. The phase rotator provides coarse adjustment over a wide range, while the phase interpolator provides fine adjustment within a smaller range. This segmentation allows the system to achieve wide overall coverage without requiring a single complex circuit to handle the entire range.
Solution Approach 2:
The system dynamically switches between coarse and fine adjustment modes based on the required phase correction magnitude. For large phase errors, the phase rotator is activated for coarse adjustment; for small phase errors, the phase interpolator provides fine adjustment. This dynamic operation optimizes the use of circuit resources.
Data Source
AI summary
A clock and data recovery device includes a data analysis circuitry, a loop filter circuitry, a phase rotator circuitry, a multiplexer circuitry, and a phase interpolator circuitry. The data analysis circuitry analyzes input data according to a first clock signal and a second clock signal to generate an error signal. The loop filter circuitry updates an adjustment signal according to the error signal. The phase rotator circuitry adjusts rotation signals according to the adjustment signal and limit values if the adjustment signal is updated. The multiplexer circuitry outputs one of the rotation signals as a phase control signal according to third clock signals. The phase interpolator circuitry adjusts the first and the second clock signals according to the phase control signal and fourth clock signals.