Clock Data Recovery Lock Detection Using Periodic Phase Accumulation
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Solution Overview
Problem
Conventional clock data recovery modules are susceptible to phase drift between transmit and receive clock signals, leading to inaccurate phase difference measurements due to wraparound conditions and lack of precise lock detection.
Innovation Solution
A clock data recovery module with a phase detector and a lock detector that accumulates phase information, determines if a code change is within a set range over a time period, and resets the accumulated total at the end of the period, ensuring accurate phase locking and mitigating phase drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional lock detection is used to determine phase locking, then the system can detect lock condition, but phase drift between TX and RX clock signals causes inaccurate phase difference measurements
Solution Approach 1:
The patent implements periodic resetting of the phase detector accumulator at predetermined intervals (e.g., every 1000 clock cycles). This periodic action prevents phase drift accumulation and wraparound errors by regularly zeroing the accumulator, allowing accurate phase difference measurements to be taken at each reset interval without the distortion of long-term drift.
Solution Approach 2:
The patent introduces an intermediary mechanism (the reset signal and counter) that mediates between the continuous phase detection process and the accumulator. This intermediary periodically interrupts the accumulation process to reset it, thereby preventing the harmful effects of phase drift while maintaining continuous phase locking capability.
2Measurement precision
If phase accumulation is performed over long time periods, then more phase samples are collected, but wraparound conditions cause significant errors in phase difference magnitude
Solution Approach 1:
The patent applies periodic resetting of the phase detector accumulator at predetermined time intervals or after a predetermined number of clock cycles. This prevents wraparound conditions by limiting the accumulation period, ensuring that the phase difference never exceeds the representable range of the accumulator while still collecting sufficient samples for accurate measurement within each period.
Solution Approach 2:
The patent uses a counter to preliminarily track the number of clock cycles elapsed since the last reset. This preliminary action allows the system to predict when the accumulator will reach its limit and reset it proactively before wraparound errors occur, maintaining measurement accuracy throughout the accumulation process.
Data Source
AI summary
A clock data recovery module and a method of operation thereof are described. In an embodiment, a data stream is received. Transitions in the data stream are detected to provide phase signaling for indicating phase relationships to the transitions detected. A lock detector receives the phase signaling. The lock detector accumulates phase information from the phase signaling and temporarily stores an accumulated total of the phase information representative of a code change, and the lock detector determines whether the code change is within a set range over a time period and resets the accumulated total at a conclusion of the time period.