Ground-Referenced Single-Ended Signaling for Low-Noise Return Paths
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Solution Overview
Problem
Single-ended signaling systems face challenges in establishing a consistent reference voltage, managing signal return impedance, and reducing power consumption and noise susceptibility, particularly due to shared power supply impedance and crosstalk issues.
Innovation Solution
A ground-referenced single-ended signaling technique is employed, utilizing a DC to DC converter with a flying capacitor and a 2:1 clocked multiplexer to drive a single-ended signaling line, with signaling currents returned directly to the ground plane, minimizing noise and impedance-related issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If single-ended signaling is used to reduce the number of conductors, then packaging constraints are relaxed, but reference voltage agreement between transmitter and receiver becomes difficult to ensure
Solution Approach 1:
The patent establishes a common ground reference plane that provides an equipotential reference for both transmitter and receiver. By returning signal currents directly to this ground plane rather than through shared power supply terminals, the system ensures both devices operate from the same voltage reference, eliminating reference voltage agreement issues while maintaining single-ended signaling's conductor efficiency.
2Device complexity
If single-ended signaling uses shared power supply terminals for current return, then circuit simplicity is maintained, but signal return path impedance increases causing noise and crosstalk
Solution Approach 1:
The patent segments the return current path by providing dedicated ground return paths for each signal conductor rather than using shared power supply terminals. This segmentation reduces the impedance of each return path and prevents return currents from one signal from coupling into other signals, thereby reducing crosstalk and noise while maintaining circuit simplicity.
Solution Approach 2:
The patent introduces a ground reference plane as an intermediary return path between the signal conductor and the power supply system. This ground plane serves as a low-impedance mediator that carries return currents directly back to the transmitter without passing through other signal paths, thereby eliminating the crosstalk and noise problems associated with shared power supply terminals.
3Device complexity
If single-ended signaling drives current through power supply terminals, then power delivery is simplified, but power consumption increases compared to differential signaling
Solution Approach 1:
The patent uses a ground reference plane as an intermediary that allows single-ended signaling to achieve power efficiency comparable to differential signaling. By returning currents through this dedicated ground path rather than through shared power supply terminals, the system reduces the current that must be driven through high-impedance power delivery networks, thereby reducing power consumption while maintaining simplified power delivery architecture.
4Area of stationary object
If single-ended signaling uses shared return paths, then conductor count is reduced, but the return current flow creates voltage drops in shared impedance causing noise
Solution Approach 1:
The patent segments the return current paths by providing dedicated ground return paths for each signal rather than using shared power supply terminals. This segmentation ensures that return currents from different signals do not share common impedance, eliminating the voltage drops and noise that result from current summation in shared paths, while maintaining the reduced conductor count advantage of single-ended signaling.
Data Source
AI summary
One embodiment of the present invention sets forth a mechanism for transmitting and receiving ground-referenced single-ended signals. A transmitter combines a direct current (DC) to DC converter including a flying capacitor with a 2:1 clocked multiplexer to drive a single-ended signaling line. The transmitter drives a pair of voltages that are symmetric about the ground power supply level. Signaling currents are returned to the ground plane to minimize the generation of noise that is a source of crosstalk between different signaling lines. Noise introduced through the power supply is correlated with the switching rate of the data and may be reduced using an equalizer circuit.