PLL Jitter Detection Circuit for Automatic Loop Bandwidth Control
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Solution Overview
Problem
Conventional jitter detection implementations are unsuitable for ultra-low jitter phase-locked loops (PLLs), particularly in 5G applications, due to limited resolution and high power consumption, which prevents accurate jitter detection and requires costly and time-consuming tuning processes.
Innovation Solution
The implementation of a jitter detection circuit using voltage-based or time-based techniques, incorporating a comparator, digital accumulator, and narrow-range digital-to-analog converter (DAC) or digital-to-time converters (DTCs), which provides higher resolution and lower power consumption, allowing for automatic loop bandwidth adjustment to minimize PLL output jitter and integrated phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional jitter detection implementations are used, then the system can detect jitter, but the resolution is limited and power consumption is high
Solution Approach 1:
The jitter detection function is segmented into two distinct circuits: a voltage-based jitter detection circuit for fine-grained jitter measurement and a time-based jitter detection circuit for coarse-grained jitter measurement. This segmentation allows the system to use the more power-efficient time-based circuit for general monitoring while reserving the higher-resolution voltage-based circuit for critical measurements, thus resolving the contradiction between resolution and power consumption.
Solution Approach 2:
The system dynamically switches between voltage-based and time-based jitter detection modes based on operating conditions and jitter levels. The controller selectively activates the appropriate detection circuit, enabling the system to adapt its power consumption and resolution characteristics to match current operational requirements, thereby resolving the static contradiction between power efficiency and measurement precision.
2Measurement precision
If conventional jitter detection implementations are used, then the system can detect jitter, but the testing process is costly and time-consuming
Solution Approach 1:
The controller receives jitter detection signals from both voltage-based and time-based circuits and uses this feedback to automatically adjust PLL parameters. The system continuously monitors jitter levels and dynamically tunes the loop bandwidth and other parameters to minimize jitter, eliminating the need for manual tuning processes. This closed-loop feedback mechanism resolves the contradiction by achieving high measurement precision while dramatically reducing tuning time through automation.
Solution Approach 2:
The jitter detection and control system is self-regulating, automatically detecting jitter conditions and adjusting PLL parameters without external intervention. The controller autonomously processes signals from both detection circuits and modifies system parameters to optimize performance, enabling the system to serve itself and eliminate time-consuming manual tuning operations while maintaining accurate jitter detection.
3Reliability
If automatic loop bandwidth adjustment is implemented, then the PLL output jitter is minimized, but the device complexity increases
Solution Approach 1:
The controller serves multiple functions: it processes signals from both voltage-based and time-based jitter detection circuits, determines overall jitter levels, selects appropriate detection modes, and adjusts PLL parameters. This multi-functional design consolidates what could be separate complex subsystems into a single control unit, resolving the contradiction by achieving improved PLL performance through automation while managing device complexity through functional integration.
Data Source
AI summary
Certain aspects of the present disclosure generally relate to techniques and apparatus for jitter detection using time-based and/or voltage-based techniques. An example jitter detection circuit generally includes: a comparator having a first input coupled to an input of the jitter detection circuit; a first combiner having an input coupled to an output of the comparator; an accumulator having an input coupled to an output of the first combiner, an output of the accumulator being coupled to an output of the jitter detection circuit; and a digital-to-analog converter (DAC) having an input coupled to the output of the accumulator, an output of the DAC being coupled to a second input of the comparator.