USB 2.0 Boost Circuit for Signal Edge Enhancement
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Solution Overview
Problem
Universal Serial Bus (USB) 2.0 protocols face challenges in maintaining signal integrity over long distances due to lossy channels, particularly in environments like the BladeCenter chassis, where existing solutions such as USB hubs, pre-emphasis, equalization, and transmission line matching networks are not effective in preventing channel losses that cause the received signal to fail the USB receive eye mask.
Innovation Solution
A boost circuit is connected to the USB channel to enhance signal edges without impacting the bi-directional nature of the bus, using an op-amp configuration with input and high-pass filters to minimize path delays and hub hops, ensuring compatibility with all USB signaling protocols and not adding additional DC load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If USB 2.0 is implemented over long distances through FR4 with multiple passive FET switches and connectors, then the topology flexibility is improved, but the channel loss increases causing signal to fail the USB receive eye mask
Solution Approach 1:
A boost circuit is introduced as an intermediary device on the USB bus channel to compensate for signal degradation. The boost circuit includes a booster that couples to the differential pair and actively boosts signal edges without requiring changes to USB endpoints or controllers, thereby maintaining topology flexibility while reducing channel loss effects
Solution Approach 2:
The boost circuit dynamically adjusts signal parameters by boosting edges of USB signals. The circuit uses a high-pass filter to selectively boost high-frequency edge transitions while blocking DC components, changing the signal waveform parameters to overcome channel loss without altering the fundamental USB protocol
2Reliability
If a USB hub is added to the middle of the channel, then the signal integrity is improved, but the device complexity and path delays increase
Solution Approach 1:
The boosting function is extracted from the complex USB hub architecture and implemented as a simple passive boost circuit that couples directly to the differential pair. This extraction eliminates the need for complex ASIC logic, path delay management, and hub hop protocols while maintaining signal integrity through simple edge boosting
3Reliability
If pre-emphasis and equalization are implemented, then the signal quality is improved, but the operability is limited as both endpoints must support these features
Solution Approach 1:
The boost circuit serves as an intermediary that provides signal quality improvement without requiring endpoint cooperation. Unlike pre-emphasis and equalization that require both endpoints to support the features, the passive boost circuit simply couples to the differential pair and boosts edges unilaterally, maintaining full operability with any USB 2.0 endpoint
Solution Approach 2:
The boost circuit performs self-service by automatically boosting signal edges without requiring configuration or coordination with USB endpoints. The circuit uses a high-pass filter and booster that naturally respond to edge transitions, providing signal quality improvement autonomously without impacting endpoint operation or requiring endpoint awareness of the boosting function
4Reliability
If transmission line matching network is used, then the signal reflections are reduced, but the transmit voltage must be boosted which is not specified in USB 2.0
Solution Approach 1:
The boost circuit acts as an intermediary that addresses signal degradation without requiring transmit voltage boosting. The circuit couples to the differential pair and provides edge boosting through a high-pass filter and amplifier stage, reducing reflections and improving signal quality while maintaining USB 2.0 voltage specifications at endpoints
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
This solution allows USB 2.0 implementation in unanticipated topologies without channel losses, maintaining signal integrity and compliance with USB receive eye mask requirements, as demonstrated by simulations showing improved signal quality and reduced reflections.
Implementation Method 1
a boost circuit connected at a predetermined location on the bus channel; wherein edges of the plurality of USB signals are boosted
Implementation Method 2
The boost circuit includes a high-pass filter that passes edges of the USB signals and blocks other signals
Data Source
AI summary
A system for allowing a designer to implement Universal Serial Bus (USB) 2.0 in topologies not anticipated by a USB 2.0 specification and with reduced channel losses, the system comprising: a bus channel having a plurality of electrical elements; and a boost circuit connected at a predetermined location on the bus channel; a plurality of USB signals transmitted through the system; wherein edges of the plurality of USB signals are boosted without impacting the bi-directional nature of the bus channel.