PLL Frequency Calibration for DCO and TDC PVT Drift
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Solution Overview
Problem
Phase locked loops (PLLs) face performance degradation due to shifts in the characteristics of digitally controlled oscillators (DCOs) and time to digital converters (TDCs) caused by process, voltage, and temperature variations, leading to noise and frequency distortions.
Innovation Solution
A system utilizing a finite state machine (FSM) and frequency measurement circuit (FMC) for frequency domain calibration and characterization, which measures and compensates for these variations, ensuring stable clock generation by adjusting digital codes and capacitance values to maintain constant gain and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If DCO and TDC components are used in PLLs, then high frequency clock generation is achieved, but performance shifts occur due to PVT variations
Solution Approach 1:
The patent performs frequency measurements and characterizations of the DCO and TDC components before the PLL operates in normal mode. By预先 measuring the actual frequency outputs and calculating correction factors during a calibration phase, the system prepares compensation data in advance that will be used to correct performance shifts during operation, thus preventing accuracy degradation before it occurs
Solution Approach 2:
The patent implements a feedback mechanism where the measured frequency values from the DCO and TDC are fed back into the system to calculate correction factors. These correction factors are then applied to adjust subsequent operations, creating a closed-loop system that continuously compensates for PVT variations and maintains reliable performance
2Measurement precision
If frequency measurements are performed to characterize components, then accuracy is improved, but measurement time increases
Solution Approach 1:
The patent performs frequency measurements at specific discrete frequency points rather than continuously across the entire operating range. By selecting key characterization points that capture the essential PVT variation behavior, the system achieves sufficient accuracy for correction while minimizing the time required for calibration compared to exhaustive measurement approaches
Data Source
AI summary
A system for assigning a characterization and calibrating a parameter is disclosed. The system includes a frequency measurement circuit and a finite state machine. The frequency measurement circuit is configured to measure frequencies of an oscillatory signal and to generate a measurement signal including measured frequencies. The finite state machine is configured to control measurements by the frequency measurement circuit, to assign a characterization to a parameter based on the measurement signal, and to generate a calibration signal based on the characterized parameter.