Inter-Line MOSFET Switching for Differential Signal Ringing Suppression
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Solution Overview
Problem
Existing ringing suppression circuits for differential signals in transmission lines either fail to sufficiently decrease terminal impedance, leading to incomplete suppression of waveform distortions, or consume distortion energy in a way that reflects it back to other nodes, causing adverse effects.
Innovation Solution
A ringing suppression circuit with a voltage-driven inter-line switching device connected between high and low potential signal lines, which is turned on for a fixed period when a differential signal level change is detected, utilizing a series connection of inter-line switching elements to absorb distortion energy and reduce impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple MOSFETs are connected in series between power source and ground to create auxiliary switching circuit, then the terminal impedance can be temporarily decreased during signal transitions, but the on-resistance of the MOSFETs remains too high to sufficiently decrease the impedance, requiring larger FET sizes which increases circuit complexity
Solution Approach 1:
The patent introduces a dedicated inter-line switching device as an intermediary component specifically for reducing impedance between signal lines during signal transitions. This switching device acts as a mediator that directly addresses the waveform distortion problem without requiring complex auxiliary circuits with multiple MOSFETs, thereby simplifying the overall terminal circuit design while effectively suppressing ringing.
2Object-affected harmful factors
If a switch is connected between high voltage and low voltage signal lines to short-circuit them when waveform distortion is detected, then the impedance between lines becomes zero and distortion at the receiving node is reduced, but the distortion energy is reflected back to the transmitting node causing adverse effects on other nodes
Solution Approach 1:
The patent converts the harmful distortion energy into a beneficial effect by using the inter-line switching device to provide a controlled impedance reduction path. Instead of completely short-circuiting the lines which causes reflection, the switching device dissipates the distortion energy locally at the receiving node through controlled impedance matching, preventing energy reflection back to other nodes while still suppressing ringing effectively.
3Object-affected harmful factors
If terminal impedance is temporarily decreased during delay time to suppress ringing, then waveform distortion can be reduced, but the impedance reduction is not sufficient due to high on-resistance of switching devices
Solution Approach 1:
The patent changes the key parameter of inter-line impedance dynamically by introducing a dedicated inter-line switching device that specifically targets the impedance between signal lines. This parameter change approach allows for more effective impedance reduction compared to traditional methods that modify terminal impedance to ground or power source, thereby achieving superior ringing suppression with lower on-resistance requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively suppresses ringing by consuming distortion energy and reducing impedance between signal lines during signal level transitions, thereby preventing waveform distortions from propagating.
Implementation Method 1
utilizing a series connection of inter-line switching elements to absorb distortion energy and reduce impedance
Data Source
AI summary
An inter-line switching element formed of a MOSFET is provided between a pair of signal lines. When the level of a differential signal changes from high to low, a control circuit turns on the FET for a fixed period thereby to suppress ringing by decreasing the impedance between the signal lines when the level of the differential signal transitions, and causing the energy of the distortion of the differential signal waveform to be absorbed by the on-resistance of the FET.