Spread Spectrum Oscillator Regulated Loop Frequency Stability
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Solution Overview
Problem
High frequency oscillators face challenges in maintaining frequency stability across temperature and supply voltage variations, leading to poor performance in spread spectrum clock generation, which can result in increased electromagnetic interference (EMI) and reduced timing margin.
Innovation Solution
A regulated loop circuit is used to generate a clock signal, incorporating a digital delta-sigma modulator and triangular waveform generator to modulate an N divider, reducing temperature dependence and achieving accurate frequency spreading with ±2% accuracy, thereby minimizing EMI and maintaining stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional high frequency oscillators are used for spread spectrum clock generation, then frequency stability is poor due to temperature and supply voltage variations, but adding regulated loops and PLLs improves stability while increasing device complexity
Solution Approach 1:
The patent combines the regulated loop and spread spectrum modulation functions into a single integrated oscillator circuit. The regulated loop controls the oscillation frequency while the same circuit simultaneously performs spread spectrum modulation by varying the feedback divider ratio, eliminating the need for separate PLL circuits and reducing overall device complexity while maintaining frequency stability
Solution Approach 2:
The oscillator circuit performs multiple functions: it generates the clock signal, regulates its frequency through the regulated loop, and implements spread spectrum modulation all within a single circuit block. This multi-functionality reduces the number of separate components needed and simplifies the overall system architecture
2Measurement precision
If additional PLLs are added to improve frequency control accuracy, then frequency accuracy improves, but chip size and current consumption increase
Solution Approach 1:
The regulated loop is integrated directly into the oscillator circuit, allowing frequency control and accuracy improvement without requiring external or additional PLL circuits. This integration maintains high frequency accuracy while minimizing the additional area required
3Object-generated harmful factors
If traditional spread spectrum techniques are used, then EMI reduction is achieved, but frequency control accuracy deteriorates due to temperature dependence
Solution Approach 1:
The regulated loop continuously monitors the oscillation frequency and adjusts the feedback divider ratio to maintain accurate frequency control. This feedback mechanism compensates for temperature variations and supply voltage changes, ensuring both EMI reduction through spread spectrum modulation and high frequency control accuracy are achieved simultaneously
Data Source
AI summary
Devices, systems, and methods for spread spectrum clock generation are disclosed. The devices, systems, and methods generate a clock signal at a frequency and generate a voltage output based on the frequency of the clock signal, wherein the generated voltage output is indicative of the frequency of the generated clock signal. The devices, systems, and methods also compare the frequency of the clock signal generated to a desired frequency output by comparing the generated voltage output to a voltage reference and adjust the frequency of the clock signal generated based on the results of the comparison.