Bang-Bang CDR Circuit for Fast Locking and Low Jitter
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Solution Overview
Problem
Conventional CDR circuits face challenges in achieving fast phase locking, preventing jitter, and reducing power consumption, especially in high-speed data communication systems and low latency interfaces, due to delays introduced by integral control circuits and complex designs.
Innovation Solution
A CDR circuit comprising a phase detector, a voltage-controlled oscillator (VCO), a frequency control circuit, and a counter, which generates an early-late signal to adjust the phase and frequency of the VCO clock signal, eliminating the need for an integral control circuit and reducing power consumption by using a digital comparator and up-down counter for precise frequency matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an integral control circuit is used in the CDR circuit, then the frequency and phase synchronization is achieved, but the locking time is prolonged and power consumption increases
Solution Approach 1:
The patent removes the integral control circuit from the traditional CDR circuit architecture. By extracting this component, the circuit eliminates the delays and power consumption associated with integral control while maintaining frequency and phase synchronization through an alternative mechanism using a phase detector, XOR gate, and D-flip flop that directly adjusts the clock signal based on phase error detection.
Solution Approach 2:
The patent changes the control mechanism from integral control to a direct phase-error-based adjustment mechanism. The phase detector generates an early-late signal that directly controls the D-flip flop, which in turn adjusts the clock signal phase without the intermediate integration step, fundamentally changing how frequency and phase synchronization is achieved.
2Reliability
If an integral control circuit is used in the CDR circuit, then the frequency and phase synchronization is achieved, but the power consumption increases
Solution Approach 1:
The patent removes the integral control circuit from the traditional CDR circuit architecture. By extracting this component, the circuit eliminates the delays and power consumption associated with integral control while maintaining frequency and phase synchronization through an alternative mechanism using a phase detector, XOR gate, and D-flip flop that directly adjusts the clock signal based on phase error detection.
3Adaptability or versatility
If the clock signal frequency does not match the data rate, then the CDR circuit can operate with flexible frequency, but the periodicity varies causing jitter and data loss
Solution Approach 1:
The patent implements a feedback mechanism where the phase detector continuously monitors the phase difference between the clock signal and data transitions, generates an early-late signal, and feeds this back to the D-flip flop for real-time clock phase adjustment. This feedback loop ensures the clock remains synchronized with the data rate while maintaining frequency flexibility.
Solution Approach 2:
The D-flip flop is configured to advance or delay the clock signal phase in advance based on the early-late signal, preventing jitter and periodicity variations before they cause data sampling errors. This preliminary adjustment ensures data integrity is maintained even when operating with flexible frequencies.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables fast phase locking, reduces jitter, and lowers power consumption, allowing for high-speed data sampling without staggering the clock signal, thus improving data integrity and efficiency in both PON and LLI systems.
Implementation Method 1
A voltage controlled oscillator (VCO) receives an early-late signal and a frequency control code, and generates a VCO clock signal. The VCO controls a phase of the VCO clock signal based on the early-late signal. The VCO controls a frequency of the VCO clock signal based on the frequency control code.
Data Source
AI summary
A clock and data recovery circuit includes a bang-bang phase detector (BBPD), a voltage controlled oscillator (VCO), a frequency control circuit, and an up-down counter. The BBPD generates an early-late signal by determining whether serialized data received by the BBPD is early or late with respect to a VCO clock signal generated by the VCO. A phase of the VCO clock signal is controlled based on the early-late signal. The frequency control circuit compares a frequency of the VCO clock signal and a target frequency and generates an up/down signal. Based on the up/down signal, the up-down counter increments or decrements the frequency of the VCO clock signal to match the target frequency.