PLL Realignment Path With Skew Cancellation for Lock Stability
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Solution Overview
Problem
Phase locked loops (PLLs) in high-speed clock signals often exhibit anomalous behavior due to phase noise and spurious signals, leading to suboptimal output from voltage controlled oscillators (VCOs) over time, which can break the locked condition.
Innovation Solution
Implementing a realignment path with matching skew mitigation circuitry in the PLL, using identical logic gates to process signals and controlling pulse width to ensure accurate clock realignment signals are provided to the VCO, thereby maintaining the locked condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a realignment path is implemented in the PLL to correct phase drift, then the long-term stability of the VCO is improved, but the circuit complexity increases due to additional skew mitigation circuitry and matching logic gates
Solution Approach 1:
The PLL circuit is divided into distinct functional segments: the main PLL path and the separate realignment path. The realignment path is further segmented into skew mitigation circuitry and matching logic gates. This segmentation allows the realignment function to be added independently without redesigning the entire PLL, thus improving long-term stability while controlling overall circuit complexity through modular design.
Solution Approach 2:
Matching logic gates are introduced as intermediary elements between the skew mitigation circuitry and the VCO. These intermediary gates ensure precise timing alignment by compensating for skew effects, enabling the realignment path to effectively correct phase drift without directly modifying the main PLL structure, thereby maintaining a balance between stability improvement and circuit complexity.
2Measurement precision
If matching skew mitigation circuitry is used to compensate for timing skew, then the alignment precision of clock realignment signals is improved, but the device complexity increases due to additional circuit components
Solution Approach 1:
The skew mitigation circuitry is designed with local quality by using identical logic gates specifically configured for timing alignment in the realignment path. This localized optimization ensures that the critical path for clock realignment signal generation has matched skew characteristics, achieving high alignment precision without requiring complex global circuit modifications. The matching logic gates are strategically placed only where needed for skew compensation.
3Reliability
If identical logic gates are used in the realignment path to match skew, then the reliability of the locked condition is improved, but the manufacturing complexity increases due to stricter component matching requirements
Solution Approach 1:
Identical logic gates are used throughout the realignment path to ensure homogeneous timing characteristics. This homogeneity guarantees that skew effects are consistently compensated, maintaining the reliability of the locked condition. While this approach increases manufacturing complexity due to the requirement for matching components, it ensures predictable and reliable operation of the PLL realignment function.
Data Source
AI summary
Systems and methods are provided for a phase locked loop. A phase/frequency detector is configured to receive a reference signal and a feedback signal. A charge pump is configured to receive outputs from the phase/frequency detector and to generate pulses. An oscillator is configured to generate an output waveform based on the charge pump pulses. A realignment path is configured to generate a clock realignment signal that is provided to the oscillator based on the outputs from the phase/frequency detector.