Clock Data Recovery Circuit With Shift Register Ring Phase Tracking
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Solution Overview
Problem
Existing clock data recovery circuits are unable to adjust the phases of clock signals to match significant changes in data rate, such as those occurring in spread-spectrum techniques, particularly between 2.97 Gbps and 3.0 Gbps, which limits their effectiveness in synchronizing data transmission systems.
Innovation Solution
A clock data recovery circuit incorporating a phase detector, shift register ring, and phase shift circuit that generates and adjusts clock signals to track changes in data rate by shifting phases up to 5000 parts per million, using multiple feedback loops and phase interpolator circuits to accurately synchronize with data signal transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spread-spectrum techniques are used to reduce electromagnetic interference, then electromagnetic interference is reduced, but the bandwidth of the clock signal is spread which makes it difficult for traditional clock data recovery circuits to track the phase changes
Solution Approach 1:
The phase detector circuit is designed to dynamically adjust to phase changes in the clock signal caused by spread-spectrum techniques. The circuit continuously monitors phase differences and adapts its operation to track the varying phase, enabling it to handle the dynamic nature of spread-spectrum clocking while maintaining synchronization.
Solution Approach 2:
The invention changes the operational parameters of the phase detector to accommodate the spread-spectrum modulation. By adjusting the detection thresholds and response characteristics, the circuit can accurately measure phase differences even when the clock signal bandwidth is spread, thus resolving the contradiction between EMI reduction and phase tracking capability.
2Loss of energy
If the bandwidth of the clock signal is spread to reduce peak energy radiation, then peak energy radiation is reduced, but the frequency spectrum becomes wider which exceeds desirable limits for electromagnetic interference at certain frequencies
Solution Approach 1:
The phase detector circuit parameters are specifically designed to operate within the spread spectrum bandwidth while maintaining frequency selectivity. By adjusting the detection bandwidth and filtering characteristics, the circuit can track the spread clock signal without amplifying out-of-band electromagnetic interference, thus resolving the energy distribution contradiction.
3Device complexity
If traditional clock data recovery circuits are used, then circuit simplicity is maintained, but they are unable to adjust phases to match significant changes in data rate up to 5000 parts per million
Solution Approach 1:
The phase detector incorporates dynamic phase adjustment mechanisms that enable the circuit to adapt to large phase changes (up to 5000 PPM) while maintaining a relatively simple overall structure. The dynamic elements allow the circuit to respond to significant data rate variations without requiring a completely complex redesign.
Solution Approach 2:
The invention introduces intermediary phase detection and adjustment stages that bridge the gap between the simple traditional circuit architecture and the requirement for large phase tracking capability. These intermediary elements enable gradual phase adjustment while preserving the fundamental simplicity of the overall circuit design.
Data Source
AI summary
A circuit includes a phase detector circuit, a shift register ring circuit, and a phase shift circuit. The phase detector circuit generates an indication of a phase error between a periodic signal and an input signal. The shift register ring circuit shifts stored signals through a variable number of storage circuits coupled in the shift register ring circuit. The variable number of storage circuits coupled in the shift register ring circuit is determined based on the indication of the phase error. The phase shift circuit adjusts a phase of the periodic signal based on the stored signals.