PLL Disturbance Response Control for Fast Clock Settling
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Solution Overview
Problem
Phase-locked loops (PLLs) face challenges in settling quickly and maintaining stability due to disturbances such as phase acquisition and sudden changes in inputs or outputs, leading to overshoot, undershoot, and instability in the output clock.
Innovation Solution
A circuit with a phase-locked loop that includes a phase frequency detector, a loop filter, and a controller. The controller detects behaviors in the phase error and responds by adjusting the phase frequency detector and loop filter to reduce settling time and minimize overshoot and undershoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional phase-locked loop is used without disturbance response mechanisms, then the circuit structure remains simple, but the settling time increases and stability deteriorates when disturbances occur
Solution Approach 1:
The patent implements feedback mechanisms where the controller continuously monitors phase error behavior and adjusts the loop filter coefficients accordingly. This closed-loop control enables the PLL to detect disturbances and automatically correct them, improving stability without requiring a fundamentally more complex circuit architecture.
Solution Approach 2:
The system pre-configures multiple loop filter coefficient sets corresponding to different operating conditions and disturbance types. When a disturbance is detected, the controller quickly switches to the appropriate pre-configured coefficients, enabling rapid response without complex real-time calculations.
2Loss of time
If the loop bandwidth is increased to reduce settling time, then the settling time decreases, but overshoot and undershoot increase
Solution Approach 1:
The patent dynamically adjusts the loop filter coefficients based on the detected phase error behavior and operating conditions. This allows the system to optimize the balance between settling time and overshoot/undershoot for each specific situation, rather than using a fixed bandwidth setting.
Solution Approach 2:
The system changes the parameters of the loop filter (coefficients) in response to detected disturbances and phase error behaviors. By adjusting these parameters dynamically, the system can achieve fast settling without excessive overshoot or undershoot.
3Reliability
If disturbance response mechanisms are added to the phase-locked loop, then stability and settling time improve, but the device complexity increases
Solution Approach 1:
The controller performs multiple functions: it monitors phase error, detects various disturbance types, determines phase error behaviors, and adjusts loop filter coefficients. This multi-functional approach consolidates what could be separate complex circuits into a single controller unit.
Solution Approach 2:
The system monitors its own phase error behavior and automatically adjusts its parameters without external intervention. This self-service capability eliminates the need for external control circuits or manual adjustment mechanisms.
4Adaptability or versatility
If the phase-locked loop operates without behavioral detection of phase error, then the control logic remains simple, but the ability to respond to disturbances deteriorates
Solution Approach 1:
The patent replaces complex mechanical or hardware-based disturbance detection mechanisms with a software/firmware-based behavioral analysis approach. The controller analyzes phase error patterns to infer disturbance types and appropriate responses, reducing hardware complexity while maintaining adaptability.
Data Source
AI summary
A circuit for a phase-locked loop is described herein. The circuit includes a phase frequency detector configured to determine a phase error, a loop filter coupled to the phase frequency detector and configured to provide a clock control signal based on the phase error, and a controller coupled to the phase frequency detector and to the loop filter. The controller is configured to receive the phase error, detect a behavior of the phase error, and, responsive to the behavior of the phase error, perform a response that includes causing the phase frequency detector to adjust the phase error and causing the loop filter to adjust the clock control signal. Thus, the circuit may reduce settling time, overshoot, and/or undershoot in an output clock generated based on the clock control signal.