CDR Lock Detection Using Frequency Path Correction Signals
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Solution Overview
Problem
Clock and data recovery (CDR) circuits in high-speed serial communications are susceptible to phase errors due to differences in transmitter and receiver reference clock frequencies, affecting data recovery performance.
Innovation Solution
A CDR circuit comprising a phase detector, digital loop filter, and lock detector circuit that generates phase and frequency correction signals to control the phase interpolator and determine a lock condition, using internal signals to process frequency path correction signals and extract waveform features for lock detection without separate hardware for bang-bang phase detectors and leaky filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate hardware for bang-bang phase detectors and leaky filters is used, then lock detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent combines the functions of bang-bang phase detectors and leaky filters into a single integrated lock detector circuit. The lock detector uses the frequency path correction signal from the digital loop filter to determine lock condition, eliminating the need for separate hardware components while maintaining detection accuracy through unified signal processing
Solution Approach 2:
The lock detector circuit is designed to perform multiple functions: it processes frequency path correction signals, extracts waveform features, determines lock conditions, and provides timing information for integrate-and-dump operations. This multi-functional design replaces what would traditionally require separate dedicated hardware blocks
2Adaptability or versatility
If traditional lock detection methods are used, then design simplicity is maintained, but adaptability to frequency offsets decreases
Solution Approach 1:
The lock detector implements dynamic adaptability by using the frequency path correction signal to adjust its detection parameters. The circuit dynamically extracts waveform features and adapts its integrate-and-dump timing based on the actual frequency offset conditions, allowing it to function effectively across varying frequency conditions rather than being fixed to a single operating point
3Productivity
If frequency path correction signals are directly mapped to frequency offsets, then data recovery performance is improved, but measurement precision requirements increase
Solution Approach 1:
The system uses feedback through the frequency path correction signal to continuously monitor and adjust for frequency offsets. The lock detector extracts waveform features from this feedback signal and uses integrate-and-dump processing to determine lock condition, creating a closed-loop system that improves data recovery performance while managing measurement precision requirements through iterative correction
Data Source
AI summary
A clock and data recovery (CDR) circuit includes a phase detector, a digital loop filter, and a lock detector. The phase detector generates a phase detect result signal in response to phase detection of a plurality of samples. The plurality of samples are generated by sampling a received signal based on a sampling clock a sampling clock provided by a phase interpolator. The digital loop filter includes a phase path and a frequency path for providing a phase path correction signal and a frequency path correction signal based on the phase detect result signal respectively. A phase interpolator code generator generates a phase interpolator code for controlling the phase interpolator based on the phase path correction signal and frequency path correction signal. The lock detector generates a lock condition signal based on the frequency path correction signal, the lock condition signal indicating a lock condition of the CDR circuit.