Dynamic Strobe Timing for High-Speed Serial Interface Testing
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Solution Overview
Problem
Conventional testing apparatuses are unable to accurately test devices with high-speed serial interfaces due to their inability to follow variations in timing, specifically jitter, of the output data, as the strobe timing is predetermined within the apparatus.
Innovation Solution
A testing apparatus that includes a reference clock source, a clock generating circuit to reproduce a clock with the same frequency and phase as the device under test, a delay circuit to generate a strobe, a timing comparator to obtain output values based on the strobe, and a logic comparing unit to determine pass/fail results, with phase and frequency comparison units to synchronize the reproduced clock with the device's output data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a predetermined strobe timing is used in the conventional testing apparatus, then the apparatus structure is simple, but the testing accuracy for high-speed serial interfaces deteriorates due to inability to follow timing variations
Solution Approach 1:
The strobe timing is changed from a fixed predetermined value to a dynamically adjustable parameter. The testing apparatus now includes a strobe timing adjustment mechanism that allows the strobe timing to be varied and optimized based on the actual timing characteristics of the device under test, enabling accurate measurement of timing variations while maintaining operational simplicity through automated adjustment.
Solution Approach 2:
A feedback mechanism is introduced where the actual output timing of the device under test is measured and used to adjust the strobe timing automatically. The system continuously monitors timing variations and adjusts the strobe timing accordingly, ensuring that the strobe always samples at the optimal moment regardless of timing drift or jitter, thus maintaining high measurement precision without requiring complex manual calibration.
2Adaptability or versatility
If a fixed strobe timing is used, then the operation is simple, but the adaptability to different output data rates and timing variations deteriorates
Solution Approach 1:
The strobe timing is made dynamic and adjustable rather than fixed. The system includes automated timing calibration functionality that adapts the strobe timing to match the specific characteristics of each device under test and each data rate, enabling the apparatus to handle various output data rates and timing variations effectively while keeping the operation simple through automation.
Solution Approach 2:
The strobe timing parameter is changed from a fixed value to a variable parameter that can be automatically adjusted. The system measures the actual timing characteristics of the device under test and automatically modifies the strobe timing parameter to optimize sampling accuracy for different data rates and timing conditions, thereby improving adaptability without complicating the user operation.
3Reliability
If predetermined strobe timing is used, then the device complexity is low, but the reliability of testing results deteriorates due to inability to track timing variations
Solution Approach 1:
A feedback-based timing adjustment system is implemented where the actual output timing of the device under test is continuously monitored and used to automatically adjust the strobe timing. This feedback mechanism ensures that the strobe timing always corresponds to the actual timing characteristics of the device, maintaining high reliability of testing results while avoiding the need for complex manual calibration procedures through automated operation.
Solution Approach 2:
The strobe timing is transformed from a static predetermined value to a dynamic parameter that automatically adapts to timing variations. The system includes real-time timing measurement and adjustment capabilities that track timing drift and jitter, ensuring reliable testing results across different operating conditions while maintaining operational simplicity through automated adjustment mechanisms.
Data Source
AI summary
A testing apparatus includes a logic comparing unit for comparing the output value with a predetermined expectation value; a pass/fail determining module for determining pass/fail of the device under test based on the comparison result of the logic comparing unit; and a clock generating circuit including a first phase comparing unit for comparing phase of the output data of the device under test with that of the reproduced clock and outputting a first comparison result signal; a second phase comparing unit for comparing phase of the reference clock with that of the reproduced clock and outputting a second comparison result signal; and a reproduced clock generating module for generating the reproduced clock based on the first and second comparison result signals.