Spread Spectrum Clock Generator With Adaptive Modulation Limits
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Solution Overview
Problem
Conventional semiconductor integrated circuits face challenges in achieving effective electromagnetic interference (EMI) reduction due to manufacturing variations, supply voltage, and temperature fluctuations, which affect the modulation degree of clock signals, leading to reduced EMI mitigation and potential circuit malfunctions.
Innovation Solution
A spread spectrum clock generation circuit utilizing a delay control type oscillator and a maximum modulation value determination circuit to maintain a constant modulation degree, ensuring a frequency-modulated clock signal is generated regardless of manufacturing variations or environmental conditions, by adjusting the oscillation period based on a control signal and using a modulation signal generation circuit to produce a modulation control signal within a predetermined maximum value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the degree of modulation is increased to reduce EMI, then the EMI reduction effect is improved, but the maximum frequency of the clock increases causing circuit malfunction
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the modulation degree based on the operating frequency. The modulation degree is set to be inversely proportional to the operating frequency, ensuring that as frequency increases, modulation degree decreases, thereby preventing circuit malfunction while maintaining EMI reduction effectiveness across different operating conditions
2Ease of manufacture
If conventional VCO and filter circuits are used, then the circuit can operate, but manufacturing variations and environmental conditions cause modulation degree to vary reducing EMI mitigation
Solution Approach 1:
The patent employs feedback mechanisms where the operating frequency is detected and used to determine the appropriate modulation degree. This closed-loop approach compensates for manufacturing variations and environmental conditions by automatically adjusting the modulation parameters based on actual operating conditions, ensuring consistent modulation degree and effective EMI mitigation
Solution Approach 2:
The patent transitions from static modulation parameters to dynamic parameter adjustment. The modulation degree is made variable and adaptive, changing in real-time based on the operating frequency. This dynamic approach allows the system to maintain optimal performance across different manufacturing variations and environmental conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures a consistent modulation degree, preventing EMI reduction effectiveness and circuit malfunctions, while allowing for compliance with EMI standards and reducing the need for additional EMI countermeasure components.
Implementation Method 1
a delay control type oscillator for variably controlling an oscillation period thereof at an equal interval, based on a control signal
Data Source
AI summary
Disclosed is a spread spectrum clock generator which includes: a first delay control type oscillator that variably controls an oscillation period at a control period interval according to a control signal; a control circuit; a maximum modulation value determination circuit that determines a maximum modulation value from a predetermined value, a frequency control signal, and a given modulation degree setting signal; a modulation signal generation circuit that receives the maximum modulation value from the maximum modulation value determination circuit and generates a modulation control signal within the maximum modulation value; and a second delay control type oscillator that receives a value obtained by adding the modulation control signal from the modulation signal generation circuit to the frequency control signal as a control signal and variably controls the oscillation period of an output clock signal at the control period interval according to the control signal. The control circuit outputs the frequency control signal for variably controlling the oscillation period based on the result of phase comparison between a clock signal obtained by frequency dividing the output of the first delay control type oscillator and a frequency divided clock signal of a reference clock signal, performed by a phase comparator.