USB Bus Switch Circuit for Signal Quality and Disconnection Detection
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Solution Overview
Problem
USB signal transfer in high-speed mode is hindered by parasitic capacitance and resistance, leading to signal degradation, and existing technologies struggle to accurately detect device disconnection, especially in long cable configurations where reflected waves interfere with disconnection detection.
Innovation Solution
A circuit device with a bus switch circuit and disconnection detection circuit that temporarily disconnects the bus during signal transfer, allowing a wait period for disconnection detection, thereby reducing interference from reflected waves and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bus connection is maintained continuously for signal transfer, then data transmission efficiency is improved, but disconnection detection accuracy deteriorates due to reflected wave interference
Solution Approach 1:
The bus switch circuit periodically switches the bus connection between connected and disconnected states. During the disconnected state, disconnection detection is performed by monitoring for reflected waves. This periodic switching allows the system to maintain high data transmission efficiency during connected periods while achieving accurate disconnection detection during disconnected periods, thereby resolving the contradiction between transmission efficiency and detection accuracy.
2Adaptability or versatility
If cable length is increased to extend device connectivity range, then adaptability is improved, but signal quality deteriorates due to parasitic capacitance and resistance
Solution Approach 1:
The bus switch circuit acts as an intermediary that periodically disconnects the bus line. During the disconnected state, it prevents reflected waves from interfering with signal monitoring, thereby maintaining signal quality even in long cable configurations. This allows the system to extend device connectivity range while preserving reliable signal transmission and accurate disconnection detection.
Data Source
AI summary
A circuit device includes first and second physical layer circuits, a bus switch circuit that switches connection between a first bus and a second bus, which are compliant with the USB standard, ON in a first period and OFF in a second period, and a processing circuit that performs processing for transferring a packet in a transfer route constituted by the first bus, the first and second physical layer circuits, and the second bus, in the second period. The second physical layer circuit includes a disconnection detection circuit that detects device disconnection of a device connected to the second bus side. If device disconnection is detected in the second period, the connection between the first bus and the second bus is switched from off to on after a wait period has elapsed from the timing at which the device disconnection was detected.