On-chip Spread Spectrum Characterization Using Skitter Circuit
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Solution Overview
Problem
Evaluating on-chip spread spectrum clocks is challenging due to difficulties in determining whether the addition of a spread spectrum by a phase-locked loop (PLL) was successful and whether the resulting clock signal is consistent with the intended effect.
Innovation Solution
The method involves obtaining skitter data from a skitter circuit, setting an offset pointer to the center of the spread width, retrieving edge data for each reference clock cycle, incrementing an offset counter when the edge crosses the pointer, and calculating the frequency of the spread spectrum using the offset counter and the number of reference clock cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spread spectrum is added to clock signals using a phase-locked loop, then electromagnetic interference is reduced, but it becomes difficult to verify whether the spread spectrum was successfully added and whether the signal is consistent with intended effects
Solution Approach 1:
A skitter circuit is introduced as an intermediary device to measure and characterize the clock signal. The skitter circuit captures edge data and spread spectrum data, allowing verification of the spread spectrum addition without directly interfering with the clock signal itself. This mediator enables accurate measurement while preserving the signal's integrity.
Solution Approach 2:
The patent replaces traditional mechanical or direct observation methods with electronic measurement techniques. The skitter circuit uses electronic counters, pointers, and data capture mechanisms to measure the clock signal's characteristics, substituting physical verification methods with electronic characterization that can accurately detect spread spectrum effects.
2Ease of operation
If traditional measurement methods are used to evaluate clock signals, then the measurement process is simple, but it is impossible to accurately characterize the spread spectrum clock signal
Solution Approach 1:
The measurement process is segmented into distinct functional components within the skitter circuit: edge detection, spread spectrum data capture, offset pointer management, and frequency calculation. Each component handles a specific aspect of the measurement, making the complex characterization process manageable and systematic while maintaining accuracy.
Solution Approach 2:
The skitter circuit serves as an intermediary measurement device that bridges the gap between simple observation and accurate characterization. It provides a structured approach to measuring spread spectrum clock signals through systematic data capture and analysis without requiring complex external equipment.
Data Source
AI summary
On-chip spread spectrum characterization including obtaining, from a skitter circuit, skitter data comprising a spread width corresponding to an amplitude of a spread of a spread spectrum clock signal; setting an offset pointer to a center of the spread width corresponding to the amplitude of the spread; retrieving, for each of a number of reference clock cycles, edge data indicating a location, within the spread width, of an edge of the spread spectrum during the reference clock cycle; incrementing, using the edge data, an offset counter for each reference clock cycle during which the edge of the spread spectrum crosses the offset pointer; and calculating a frequency of the spread spectrum using the offset counter and the number of reference clock cycles.