On-Chip Eye Viewer Architecture for Serial Signal Analysis
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Solution Overview
Problem
High-speed serial interface signals are attenuated and distorted due to frequency-dependent signal loss, leading to intersymbol interference, which complicates visualization and correction of signal quality within integrated circuits, especially after equalization, as traditional methods like oscilloscope probing are often impossible.
Innovation Solution
An integrated circuit with eye viewer circuitry that includes a phase interpolator, threshold variable comparator, and control logic to determine the eye diagram boundaries of an equalized serial input signal, enabling two-dimensional and three-dimensional visualizations and error rate analysis, allowing for internal signal quality assessment and adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional oscilloscope probing is used to obtain eye diagrams, then signal quality can be visualized at external interfaces, but internal equalized signals cannot be measured due to sensitivity and accessibility constraints
Solution Approach 1:
The patent introduces an intermediary measurement system consisting of a tap circuit coupled to the equalized serial input signal and a boundary determination circuit. This intermediary system allows eye diagram measurement of internal signals without direct oscilloscope probing, resolving the contradiction between measurement precision and signal accessibility by creating a bridge between the sensitive internal node and the measurement capability.
2Reliability
If equalization circuitry is added to improve signal quality, then intersymbol interference is reduced, but the signal becomes more sensitive and inaccessible to traditional probing methods
Solution Approach 1:
The patent segments the measurement function from the equalization function. The equalization circuitry processes the signal to improve quality, while a separate tap circuit and boundary determination circuit handle the measurement function. This segmentation allows the equalized signal to maintain its sensitivity while being measured by a dedicated measurement path that does not interfere with the signal integrity.
Solution Approach 2:
The tap circuit acts as an intermediary that couples to the equalized serial input signal without directly probing it with an oscilloscope. This intermediary structure enables measurement of the sensitive equalized signal while maintaining signal integrity and avoiding the accessibility problems that would arise from direct probing.
3Measurement precision
If internal serial signals are measured, then post-equalization signal quality can be assessed, but the signals are distorted by RX circuitry and on-die connections making measurement difficult
Solution Approach 1:
The patent extracts the measurement function from the main signal path by using a tap circuit that couples to the equalized serial input signal. This extraction allows eye diagram measurement to be performed on the post-equalization signal while separating the measurement process from the RX circuitry and on-die connections that would otherwise cause distortion, enabling accurate assessment of signal quality after equalization.
Data Source
AI summary
Systems, methods, and devices for determining an eye diagram of a serial input signal to an integrated circuit without an oscilloscope are provided. For example, one embodiment of an integrated circuit device may be capable of determining an eye diagram associated with an equalized serial input signal. The device may include an equalizer and eye viewer circuitry. The equalizer may receive and perform equalization on a serial input signal to produce the equalized serial input signal, and the eye viewer circuitry may determine horizontal and vertical boundaries of the eye diagram associated with the equalized serial input signal.