Bang-Bang Clock Recovery Circuit for Low-Latency High-Bandwidth Links
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Solution Overview
Problem
The challenge lies in accurately restoring a clock signal with reduced latency in electronic devices, particularly in high-bandwidth communication systems where increased communication rates and complex circuit designs complicate clock signal handling, leading to stability issues and limited bandwidth.
Innovation Solution
An electronic device employing a first sample circuit, a comparator, an analog bang-bang phase detector, and a digitally controlled oscillator to generate a sampling signal, logic decision signal, detection signal, and adjust the clock signal frequency based on the detection signal, thereby reducing latency and improving bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If communication rate is increased and circuit design is made more complex to handle large amounts of data, then communication efficiency is improved, but clock signal restoration accuracy deteriorates
Solution Approach 1:
The CDR circuit is divided into multiple functional blocks: sampling circuit, logic decision circuit, phase detector, and frequency control circuit. Each block performs a specific function in the clock recovery process, allowing the system to handle high-rate communications while maintaining restoration accuracy through specialized processing at each stage.
Solution Approach 2:
The phase detector generates a detection signal based on the phase difference between the recovered clock and the sampled data, which is then fed back to the frequency control circuit. This feedback mechanism allows continuous adjustment of the clock frequency to maintain accurate synchronization even at high communication rates.
2Reliability
If components such as equalizer are used during clock signal restoration, then signal quality is improved, but latency increases
Solution Approach 1:
The patent removes the equalizer component from the clock recovery path, relying instead on the sampling circuit to directly capture signal transitions. This extraction of the equalizer eliminates its associated latency while maintaining sufficient signal quality for clock recovery through the simplified sampling and phase detection approach.
Solution Approach 2:
The sampling circuit directly captures signal transitions without passing through multiple processing stages like equalization. This skipping of intermediate processing steps reduces the time required for clock signal restoration while still achieving adequate signal quality for accurate phase detection.
3Area of stationary object
If CDR circuit size is decreased, then device integration is improved, but clock signal restoration capability deteriorates
Solution Approach 1:
Multiple functions are merged into compact circuit blocks: the sampling circuit performs both signal sampling and edge detection, the logic decision circuit combines threshold comparison and digital signal generation, and the phase detector integrates phase difference detection with detection signal generation. This merging reduces overall circuit area while maintaining restoration capability.
Solution Approach 2:
The patent replaces complex analog equalization mechanisms with digital logic-based sampling and phase detection. This substitution reduces the physical size of the CDR circuit while maintaining or improving clock restoration accuracy through digital signal processing techniques.
Data Source
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AI summary
An electronic device includes a first sample circuit configured to generate a first sampling signal by sampling an input signal in response to edges of a clock signal, a first comparator configured to generate a first logic decision signal by comparing a voltage level of the first sampling signal with a reference voltage level, an analog bang-bang phase detector configured to generate a first detection signal by executing an exclusive OR (XOR) operation on successive samples of the first logic decision signal, and a digitally controlled oscillator configured to vary a frequency of the clock signal according to the first detection signal.