Re-Driver Termination Impedance Control for Common-Mode Transients
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Solution Overview
Problem
Communication systems face signal loss due to transmission paths, necessitating re-timers and re-drivers, but sharing a termination network between transmitter and receiver in USB 3 and USB 4 protocols can lead to common mode voltage variations outside specified limits, affecting compliance.
Innovation Solution
A re-driver with a shared termination network and control circuitry adjusts impedance to compensate for transients in common mode voltage, ensuring compliance by minimizing voltage variations within USB 3 and USB 4 limits during transmitter and receiver enablement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a shared termination network is used between transmitter and receiver, then device complexity is reduced, but common mode voltage variations occur outside specified limits
Solution Approach 1:
The patent applies dynamics by making the termination impedance adjustable rather than fixed. The control circuitry dynamically changes the termination impedance value based on the operational state (transmitter enablement, receiver enablement, or steady-state) to compensate for common mode voltage transients. This dynamic adjustment resolves the contradiction by maintaining voltage compliance while using a shared termination network structure.
Solution Approach 2:
The patent changes the termination impedance parameter from a constant value to a variable value that adapts to different operational conditions. By modifying the impedance parameter in response to common mode voltage transients during transmitter or receiver enablement, the system maintains compliance with voltage specifications while benefiting from the simplified shared termination network architecture.
2Reliability
If termination impedance is adjusted to compensate for transients, then common mode voltage compliance is improved, but device complexity increases
Solution Approach 1:
The control circuitry is designed to perform multiple functions: detecting common mode voltage transients, determining the appropriate termination impedance value, and adjusting the termination network. This multi-functional approach consolidates what could be separate complex circuits into a single integrated control mechanism, resolving the contradiction between compliance and complexity.
Solution Approach 2:
The system employs feedback by monitoring the common mode voltage and using this information to adjust the termination impedance. The control circuitry receives feedback about voltage transients during transmitter or receiver enablement and automatically compensates by changing the termination impedance, thereby maintaining compliance without requiring overly complex external control mechanisms.
3Productivity
If transmitter or receiver is enabled, then signal transmission capability is improved, but common mode voltage transients occur
Solution Approach 1:
The system applies preliminary anti-action by pre-adjusting the termination impedance before or during the enablement of the transmitter or receiver. The control circuitry detects the impending transient condition and proactively changes the termination impedance to counteract the voltage variation, thereby allowing signal transmission capability to improve while preventing harmful voltage transients.
Solution Approach 2:
The control circuitry performs preliminary action by preparing the termination network in advance of the transient condition. When transmitter or receiver enablement is detected, the termination impedance is adjusted beforehand or concurrently to minimize the impact of the resulting common mode voltage transient, enabling productive signal transmission without harmful side effects.
Data Source
AI summary
An example apparatus includes a termination network having a first input terminal coupled to a first input/output terminal and a second input terminal coupled to a second input/output terminal. The apparatus includes transmitter circuitry having a first output terminal coupled to the first input/output terminal and a second output terminal coupled to the second input/output terminal. The apparatus includes receiver circuitry having a first input terminal coupled to a first output terminal of the termination network and a second input terminal coupled to a second output terminal of the termination network. The apparatus includes control circuitry coupled to a third input terminal of the termination network, the control circuitry to: change an impedance of the termination network to compensate for a transient in a common mode voltage; and based on the common mode voltage reaching a steady state value, change the impedance of the termination network for steady state operation.