Clock and Data Recovery Circuit With Instant Phase Error Correction
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Solution Overview
Problem
High-speed integrated circuits face challenges in implementing clock and data recovery (CDR) circuits due to increased noise and frequency offsets, making it difficult to operate at higher frequencies within hardware limitations, and existing solutions struggle to instantly adjust high-speed data signals.
Innovation Solution
A clock and data recovery circuit is designed with a sampling module, phase detect module, parallel-to-serial converter, and phase adjust module, which generates and adjusts clock signals to correct phase errors instantly, utilizing phase locked loops and interpolators to maintain high phase updating rates while reducing hardware limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the operating frequency of the CDR circuit is increased to tolerate more frequency offsets, then the ability to handle frequency offsets improves, but hardware implementation becomes difficult due to hardware limitations
Solution Approach 1:
The CDR circuit is divided into multiple functional modules: a phase detector that operates at a lower frequency to detect phase errors, and a phase interpolator that generates multiple phase-shifted clock signals. This segmentation allows the phase detection function to operate at a manageable frequency while still supporting high-frequency data recovery through the interpolated clock signals.
Solution Approach 2:
A phase interpolator is introduced as an intermediary component between the phase detector and the data sampling stage. The interpolator takes the phase error signal from the detector and generates multiple phase-shifted versions of the clock signal, enabling the system to handle frequency offsets without requiring the entire CDR circuit to operate at extremely high frequencies.
2Speed
If the phase step adjusted by the CDR circuit in a unit of time is enlarged to increase operating frequency, then the operating frequency improves, but the CDR circuit cannot instantly adjust the high-speed data signal
Solution Approach 1:
The phase interpolator pre-generates multiple phase-shifted clock signals (e.g., 0°, 90°, 180°, 270°) in advance. When a phase error is detected, the system can immediately switch to the appropriate pre-generated phase without waiting for gradual adjustment, enabling instant phase correction and reducing the time loss associated with frequency adjustments.
3Productivity
If the CDR circuit operates at higher frequency to maintain phase updating rate, then phase correction speed improves, but hardware limitations are exceeded
Solution Approach 1:
The circuit separates the phase detection function (operating at lower frequency with the phase detector) from the clock signal generation function (operating at higher frequency with the phase interpolator). This allows the phase updating rate to be maintained at high speeds through the interpolator while the detector operates at a frequency that does not exceed hardware capabilities.
Data Source
AI summary
A clock and data recovery circuit includes a sampling module, a phase detect module, a parallel-to-serial converter and a phase adjust module. The sampling module generates a data signal and an edge signal according to input data, a first clock signal and a second clock signal. The phase detect module detects a phase of the data signal and a phase of the edge signal to generate first output recovered data and a first phase adjust signal. The parallel-to-serial converter performs a parallel-to-serial conversion on the first recovered data and the first phase adjust signal, so as to generate second output recovered data and a second phase adjust signal. The phase adjust module generates the first clock signal and the second clock signal, and adjusts the first clock signal and the second clock signal according to the second output recovered data and the second phase adjust signal.