Closed-Loop PLL VCO Range Calibration for Jitter Control
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Solution Overview
Problem
Phase lock loop (PLL) circuits face challenges in maintaining optimal operation ranges and reducing jitter sensitivity due to varying process corners, which require adjusting the voltage-controlled oscillator (VCO) gain and input voltage, leading to potential frequency disturbances and charge-pump current mismatches.
Innovation Solution
The PLL circuitry is configured with closed-loop continuous auto-calibration, using calibration circuitry to monitor and adjust the VCO's operating frequency range, ensuring the control voltage remains near the middle of the supply voltage, thereby maintaining a small VCO gain and minimizing jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If VCO gain is increased to cover higher and/or lower operating frequencies, then the frequency range is expanded, but the jitter sensitivity increases due to larger frequency disturbances from small voltage changes
Solution Approach 1:
The patent implements dynamic adjustment of VCO gain through multiple operating frequency range settings. The system can switch between different gain values (Kvco) depending on the required output frequency range. This allows the PLL to use lower gain settings for frequency ranges where high precision is needed, and higher gain settings when expansive frequency coverage is prioritized, thereby dynamically balancing adaptability with jitter sensitivity.
Solution Approach 2:
The patent changes the VCO gain parameter (Kvco) by selecting different operating frequency range settings. Each setting corresponds to a different gain value, allowing the system to optimize the V-F curve slope according to the application requirements. This parameter adjustment enables the system to maintain control voltage within optimal ranges while covering the necessary frequency spectrum.
2Speed
If control voltage Vcnt is pushed to extreme values to achieve required frequency at slow process corner, then the frequency requirement is met, but charge-pump current mismatch increases and headroom is reduced
Solution Approach 1:
The patent dynamically adjusts the VCO operating frequency range setting based on process corner detection. For slow process corners, the system selects a lower gain setting that keeps the control voltage within the optimal range, avoiding the need to push Vcnt to extreme values. This dynamic adaptation ensures that charge-pump current matching is maintained while still achieving the required frequency output.
Solution Approach 2:
The patent employs a feedback mechanism that monitors the control voltage Vcnt and adjusts the operating frequency range setting accordingly. When Vcnt approaches extreme values that would cause charge-pump current mismatch, the feedback system switches to a different gain setting that brings Vcnt back into the optimal range, thereby maintaining current matching while meeting frequency requirements.
3Reliability
If Vcnt is kept near middle range of power supply voltage to avoid charge-pump current mismatch, then current matching is improved, but the ability to reach extreme frequencies is reduced
Solution Approach 1:
The patent makes the VCO gain dynamic rather than fixed. The system can switch between multiple operating frequency range settings, each with different gain values. This allows the charge pump to operate with optimal current matching at moderate frequencies, while still being able to reach extreme frequencies when needed by switching to appropriate gain settings, thus dynamically balancing reliability with adaptability.
Solution Approach 2:
The patent implements a multi-functional VCO that can operate in multiple frequency ranges with different gain characteristics. By providing multiple operating frequency range settings, the system achieves universality - it can maintain optimal charge-pump current matching for routine operation while also having the capability to extend to extreme frequencies when required, serving both reliability and adaptability needs.
Data Source
AI summary
Systems and methods involving phase-locked-loop (PLL) circuitry are disclosed. In one illustrative implementation, a PLL circuit device may comprise voltage controlled oscillator (VCO) circuitry having a bias signal that sets a frequency range, circuitry that shifts the VCO circuitry to operate in one of the frequency ranges, and other circuitry to compare/calibrate signals and/or set the bias current. According to further implementations, as a function of operation of the circuitry, an operating frequency range of the VCO circuitry may be shifted to a different operating frequency range, and closed-loop, continuous frequency range, auto-calibration or other features may be provided.