Digital Clock Spectrum Spreading With Variable Divider Dithering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional circuits for spreading the clock spectrum in digital circuits consume high current and occupy large die area due to the inclusion of both digital and analog components, making them costly and inefficient for low-power applications.
Innovation Solution
A digital circuit method that generates a spread-spectrum clock train by using a temporally-varying divider value to modulate the clock train, creating a dithered clock train, which is then accumulated to produce a frequency modulation waveform, and subsequently a phase modulation signal, allowing for the calculation of a temporally-varying divider value to generate a spread-spectrum clock train with reduced power consumption and smaller die area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional digital modulators and analog phase interpolators are used to spread clock spectrum, then clock spectrum spreading functionality is achieved, but current consumption increases and die area increases
Solution Approach 1:
The patent extracts and removes the analog phase interpolator component from the traditional clock spectrum spreading circuit, retaining only the digital modulator functionality. This extraction eliminates the high current consumption and large die area associated with analog components while preserving the essential clock spectrum spreading function through digital techniques alone.
Solution Approach 2:
The patent substitutes the analog phase interpolator (analog system) with a purely digital implementation using digital modulators and digital signal processing techniques. This replacement transitions from analog to digital domain, achieving the same spectral spreading function with significantly reduced power consumption and smaller footprint suitable for integrated circuits.
2Reliability
If traditional digital modulators operating at free running clock frequency are used, then clock train modulation is achieved, but current consumption increases
Solution Approach 1:
The patent implements a dynamically adjustable digital modulator that can operate at variable frequencies rather than being fixed at the free running clock frequency. This dynamic operation allows the modulator to adapt its operating frequency to match the actual clock train frequency, reducing unnecessary switching activity and current consumption while maintaining effective modulation functionality.
Solution Approach 2:
The patent changes the operating parameters of the digital modulator, specifically allowing the modulation frequency to vary and be optimized for different operating conditions. By adjusting the modulation frequency parameter to match the actual clock frequency rather than operating at a fixed high frequency, the modulator achieves effective clock train modulation with reduced current consumption.
3Manufacturing precision
If analog phase interpolators with high linearity are used, then spread-spectrum clock pulse quality is improved, but die area increases and manufacturing cost increases
Solution Approach 1:
The patent removes the analog phase interpolator component entirely from the circuit architecture, eliminating the need for high linearity analog devices. The clock pulse quality function is instead achieved through digital signal processing techniques that do not require large-area high-precision analog components, thereby reducing die area while maintaining functionality.
Solution Approach 2:
The patent uses digital copying and processing of clock signals to achieve the spectral spreading function. Instead of relying on precise analog phase interpolation, the system uses digital modulation and signal generation to create the spread-spectrum clock train, replacing the need for expensive, large-area high-linearity analog components with smaller digital equivalents.
4Reliability
If both digital and analog circuits are included in clock spectrum spreading circuit, then clock spectrum spreading functionality is achieved, but die area increases
Solution Approach 1:
The patent segments the clock spectrum spreading function into purely digital sub-functions, separating the modulation, frequency multiplication, and spectral spreading operations into distinct digital circuit blocks. This segmentation allows each function to be implemented efficiently in digital logic without requiring analog components, reducing overall die area while maintaining complete functionality.
Solution Approach 2:
The patent substitutes the analog portion of the traditional hybrid circuit with a fully digital implementation. The analog phase interpolator and associated analog signal paths are replaced with digital modulators, digital frequency synthesizers, and digital signal processing circuits, achieving the same clock spectrum spreading function with significantly reduced die area suitable for modern integrated circuits.
Data Source
AI summary
A digital circuit configured to spread a clock train spectrum includes a clock configured to generate the clock train, and a variable divider configured to divide the frequency of the clock train by a temporally-varying-divider value to modulate the clock train and generate a dithered clock train. The circuit further includes a first accumulator configured to accumulate the dithered clock train to generate a frequency modulation waveform, and a second accumulator configured accumulate the frequency modulated waveform to generate a phase modulation signal. The circuit further includes a phase-value calculator configured to calculate the temporally-varying divider value based on the phase modulation signal; and a closed-loop control circuit configured to track and filter the modulation of the dithered clock train to generate a second clock train that is the spread spectrum of the first mentioned clock train.