Isolated USB Repeater With Periodic Suspend Signaling
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Solution Overview
Problem
USB repeaters with galvanic isolation struggle to meet the USB 2.0 standard's suspend mode power requirement of 2.5 milliamps due to continuous current consumption by isolation channels using on-off keying, leading to potential device shutdown during suspend mode.
Innovation Solution
The isolation channels on both the host and peripheral sides of the USB repeater are periodically enabled to transmit signals, utilizing independent timers and clocks to ensure synchronized entry and exit from suspend mode without additional handshake operations, thereby reducing current consumption below 2.5 milliamps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation channels are continuously enabled to maintain communication, then communication reliability is improved, but current consumption exceeds the USB suspend mode requirement of 2.5 milliamps
Solution Approach 1:
The isolation channels are enabled periodically rather than continuously during suspend mode. The host side enables the isolation transceiver at periodic intervals (e.g., every few milliseconds) to send keep-alive signals, allowing the system to maintain communication capability while keeping average current consumption below the 2.5mA USB suspend mode threshold.
Solution Approach 2:
The system dynamically adjusts the state of isolation channels based on operational requirements. During suspend mode, the isolation transceiver transitions between enabled and disabled states according to a periodic schedule, rather than maintaining a fixed continuous state, thereby adapting power consumption to actual communication needs.
2Use of energy by moving object
If isolation channels are disabled to reduce current consumption, then power savings are achieved, but communication synchronization between host and peripheral is lost
Solution Approach 1:
The periodic enabling of isolation channels ensures that synchronization information is transmitted at regular intervals even during suspend mode. This periodic communication maintains the synchronization state between host and peripheral devices while keeping power consumption within USB suspend mode limits.
Solution Approach 2:
The system performs preliminary actions by enabling the isolation transceiver periodically before complete disconnection occurs. These periodic keep-alive signals prevent the loss of synchronization information that would occur if the isolation channels were completely disabled, thereby maintaining communication readiness.
3Reliability
If different timer values are used on host and peripheral sides to account for clock variations, then synchronized suspend mode entry is achieved, but device complexity increases
Solution Approach 1:
The system adjusts timer parameters (specifically the suspend timeout values) on the host and peripheral sides to account for clock frequency variations. By calibrating these timer parameters during manufacturing or initialization, the system achieves reliable synchronized suspend mode entry despite differences in clock speeds, without requiring complex real-time synchronization protocols.
Data Source
AI summary
In an example, a method of operating a repeater having an isolation barrier to isolate a host side of the repeater from a peripheral side of the repeater, the repeater operable to be coupled to a universal serial bus (USB), includes causing the host side to enter into a suspend mode. The method also includes, responsive to entering the suspend mode, disabling a host isolation transceiver at the host side. The method includes periodically enabling the host isolation transceiver to transmit a data signal from the host side to the peripheral side. The method includes exiting the suspend mode. The method also includes enabling the host isolation transceiver.