Digital Spread Spectrum Clock Circuit for EMI and Adjustability

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Solution Overview

Problem

Conventional spread spectrum clock generating circuits face challenges in reducing electromagnetic interference (EMI) while increasing clock speed, and they have high costs and limited adjustability due to the use of analog components.

Innovation Solution

A digital spread spectrum clock generating system is introduced, comprising a digital frequency detecting unit, a digital loop filtering unit, a digital spread spectrum controlling unit, a digital-analog converting unit, and an analog controlled oscillating unit, which allows for improved cost-effectiveness and adjustability by converting digital signals to analog signals to generate a spread spectrum clock signal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a conventional spread spectrum clock generating circuit using analog components is employed, then the EMI can be reduced, but the cost increases and adjustability is limited

Engineering Contradiction:

ImproveEMIVSAvoidadjustability

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent replaces the conventional analog loop filter with a digital loop filter implemented through digital frequency detecting unit, digital loop filtering unit, and digital-analog converting unit. This substitution of analog components with digital components enables programmable adjustability while maintaining the EMI reduction functionality of the spread spectrum clock generation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent enables adjustable parameters such as spread spectrum percentage, modulation index, and frequency deviation through digital control. The digital loop filter allows dynamic adjustment of filter coefficients and characteristics, providing versatility without compromising the EMI mitigation performance.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If a conventional spread spectrum clock generating circuit using analog components is employed, then the EMI can be reduced, but the cost increases

Engineering Contradiction:

ImproveEMIVSAvoidcost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent replaces expensive analog components (analog loop filter, analog voltage controlled oscillator) with digital equivalents (digital loop filter, digital-analog converting unit). This reduces component count and manufacturing complexity while maintaining the EMI reduction capability through digital implementation of the same control functions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If clock speed is increased to improve digital electronic device performance, then the data processing speed increases, but the electromagnetic interference becomes serious

Engineering Contradiction:

Improvedata processing speedVSAvoidEMI

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful EMI generated by high-speed clock signals into a beneficial spread spectrum signal. By intentionally modulating the clock signal with a triangle wave to create frequency deviation, the energy is spread across a wider bandwidth, reducing peak EMI while maintaining the high data processing speed capability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent employs periodic triangle wave modulation to the clock signal frequency, creating a spread spectrum effect. The periodic modulation causes the clock energy to distribute across multiple frequencies rather than concentrating at a single frequency, thereby reducing EMI while preserving the overall clock speed for high-performance operation.

Inventive Principle:

Principle #19Periodic action

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

The system effectively reduces EMI and enhances the adjustability and cost-effectiveness of the clock generating circuit, improving the performance of digital electronic devices by optimizing the configuration of the spread spectrum clock generating circuit.

Implementation Method 1

the digital-analog converting unit is configured for converting the clock controlling signal to a first controlling signal and for converting the spread spectrum signal to a second controlling signal

Methodology Applied

Scientific EffectDigital-to-Analog Conversion:

Data Source

PatentUS11061430B1Spread spectrum clock generating system

Publication Date: 2021.07.13 LUMISSIL MICROSYSTEMS LTD

AI summary

A spread spectrum clock generating system is provided. The digital frequency detecting unit is configured for receiving a reference signal and a feedback signal and for comparing the reference signal and the feedback signal to generate a frequency difference signal. The digital loop filtering unit is signally connected to the digital frequency detecting unit and outputs a clock controlling signal based on the frequency difference signal. The digital spread spectrum controlling unit is configured for receiving the reference signal to output a spread spectrum signal. The digital-analog converting unit is configured for converting the clock controlling signal to a first controlling signal and for converting the spread spectrum signal to a second controlling signal. The analog controlled oscillating unit is configured for receiving the first controlling signal and the second controlling signal to output a spread spectrum clock signal.