Sampler Circuit Calibration via Virtual AFE Input Shorting
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Solution Overview
Problem
Advanced single-ended links in high-performance computing are prone to noise and inter symbol interference due to cross talk, requiring accurate offset cancellation in receiver samplers, which existing calibration methods either introduce additional interference or require power-intensive retraining.
Innovation Solution
A method for calibrating sampler offsets by tuning the AFE output to a reference voltage, creating a virtual short between sampler inputs, allowing offset reduction without physical disconnection and eliminating the need for special training patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If physical switches are used to disconnect AFE from sampler inputs during calibration, then offset calibration can be performed, but additional inter symbol interference is introduced
Solution Approach 1:
The patent introduces a virtual short mechanism as an intermediary between the AFE output and sampler inputs. Instead of using physical switches that cause interference, the invention creates a virtual connection through controlled signal paths that allow offset calibration without introducing harmful interference. The virtual short is achieved by routing signals through specific circuit paths that simulate a direct connection without the physical discontinuities caused by switches.
2Measurement precision
If system level calibration with training patterns is used, then sampler offsets can be calibrated, but additional power consumption and reduced throughput occur
Solution Approach 1:
The patent implements a self-service calibration mechanism where the receiver circuit calibrates its own sampler offsets using its existing operational signals. Instead of requiring external training patterns and back-channel communication that consume additional power, the system uses its own AFE output and internal signal paths to perform calibration autonomously during normal operation, eliminating the need for separate power-intensive calibration sequences.
3Adaptability or versatility
If physical switches are used for calibration, then offset path can be disconnected, but kickback noise mismatch between calibration and operational modes increases
Solution Approach 1:
The patent employs dynamic signal path routing that continuously adapts between calibration and operational modes without abrupt transitions. Instead of using static physical switches that create discrete state changes and kickback noise, the invention dynamically reconfigures signal paths through controlled switches and resistive networks that maintain continuous, smooth transitions. This dynamic approach ensures that the electrical characteristics seen by the sampler remain consistent across mode changes, minimizing kickback noise mismatch.
Data Source
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AI summary
For receiver circuits, Sampler offset calibration techniques are provided. In some embodiments, an output of an analog front end circuit may be tuned to a reference level that is used for an input of the sampler, and the sampler may then be calibrated to reduce an offset between its inputs.