Single-Ended Reference Voltage Calibration for Noise Tracking
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Solution Overview
Problem
Generating a high-quality reference voltage with accurate DC level and proper AC noise characteristic in single-ended signaling systems is challenging due to DC offsets and mismatched noise spectra between transmitter and receiver, which affects data rate and timing margin.
Innovation Solution
The solution involves isolating noise from the positive and ground nodes on both the transmitter and receiver sides, using coupling and decoupling circuits to ensure the reference voltage tracks ground node noise while being isolated from positive node noise, and calibrating the DC level using receiver-side circuits to compensate for offsets and adjust the reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reference voltage is generated using intrinsic AC noises in the reference voltage, then the reference voltage can offset corresponding AC noise spectrum in the received signal, but the noise spectrum in Vdd and Vss on transmitter may be different from noise spectrum in Vdd and Vss on receiver, making it extremely difficult to accurately track AC noises
Solution Approach 1:
The patent introduces a noise tracking signal as an intermediary that is explicitly coupled to the ground node noise on the transmitter side. This intermediary signal carries the ground node noise characteristics through the transmission channel to the receiver, where it is used to generate the reference voltage. This mediator enables accurate noise tracking despite differences in Vdd and Vss noise spectra between transmitter and receiver.
Solution Approach 2:
The patent extracts the ground node noise component from the power supply system by explicitly coupling the noise tracking signal to the ground node. This extracted noise signal is then separated from the main signal path and used specifically for generating the reference voltage, allowing the system to utilize only the relevant ground node noise characteristics while ignoring mismatches in Vdd noise spectra.
2Object-affected harmful factors
If the reference voltage includes AC noise spectrum to offset noise in received signal, then noise cancellation can occur, but it is extremely difficult to accurately track AC noises due to different noise spectra in Vdd and Vss between transmitter and receiver
Solution Approach 1:
The patent applies local quality by making the reference voltage generation process specific to ground node noise tracking. Instead of attempting to track all noise sources (Vdd and Vss) equally, the system focuses locally on extracting and tracking only the ground node noise characteristics. This localized approach to noise tracking enables accurate noise cancellation for the relevant ground-referenced signal while avoiding the complexity of matching all power supply noise spectra.
3Measurement precision
If DC offsets arise from circuit mismatches between transmitter and receiver, then accurate DC level of reference voltage is compromised, but adding calibration circuits increases system complexity
Solution Approach 1:
The patent implements self-service through automatic calibration circuits that perform DC level adjustment without external intervention. The calibration system uses the transmitted calibration pattern and receiver's own resources (amplifier, sampler, control logic) to automatically detect and correct DC offsets. This self-calibrating mechanism eliminates the need for manual adjustment while maintaining accurate DC level, and the calibration function is integrated into the existing receiver architecture rather than adding completely separate complex subsystems.
4Measurement precision
If intrinsic DC offsets within amplifier and sampling circuits on receiver are present, then accurate DC level of reference voltage is affected, but calibration processes increase device complexity
Solution Approach 1:
The patent merges the DC calibration function with the existing signal processing path by using the same amplifier and sampler that process data signals. The calibration pattern is processed through these existing circuits, and the same control logic that manages data reception is used to manage calibration. This merging approach allows DC offset correction without adding completely separate calibration hardware, thereby reducing overall system complexity while maintaining accurate DC level.
Data Source
AI summary
A signal on a transmitter tracks noise on a ground node in a manner decoupled from a positive node of a power supply. The signal is transmitted from the transmitter to the receiver. A reference voltage is generated on the receiver to track noise on a ground node in the receiver. Consequently, the received signal and the reference voltage have substantially the same noise characteristics, which become common mode noise that can be cancelled out when these two signals are compared against each other. In a further embodiment, the reference voltage is compared against a predetermined calibration pattern. An error signal is generated based on a difference between the sampler output and the predetermined calibration pattern. The error signal is then used to adjust the reference voltage so that the DC level of the reference voltage is positioned substantially in the middle of the received signal.