USB Host Data Switch Equalization for Parasitic Capacitance
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Solution Overview
Problem
The integration of additional components with USB-C ports in mobile devices leads to significant parasitic capacitance on differential transmission lines, causing increased insertion loss and limiting data transmission rates above 100MHz, necessitating a solution to reduce this capacitance.
Innovation Solution
Incorporation of an integrated equalizer that applies negative capacitance and conductance to the USB differential transmission lines to cancel out parasitic capacitance, thereby reducing insertion loss and enhancing data transmission rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional components (switching devices, audio circuitry, ESD devices, traces, flex connectors) are integrated with USB-C ports to provide audio and charging functionality, then device versatility and functionality are improved, but parasitic capacitance on differential transmission lines increases causing insertion loss and limiting data transmission rates
Solution Approach 1:
A common mode voltage generator is introduced as an intermediary component between the power source and the differential transmission lines. This generator produces a common mode voltage that is coupled to both DP and DN lines, serving as a mediator that counteracts the harmful effects of parasitic capacitance by maintaining stable voltage levels and enabling higher data transmission rates despite the presence of multiple integrated components
2Adaptability or versatility
If multiple components are coupled to USB differential transmission lines DP/DN, then audio and charging functionality are enabled, but insertion loss increases at frequencies above 100MHz
Solution Approach 1:
The common mode voltage generator operates with feedback mechanisms that continuously monitor and adjust the voltage levels on the differential transmission lines. By detecting voltage deviations caused by parasitic capacitance and insertion loss, the generator dynamically compensates to maintain stable signal transmission, thereby reducing energy loss at high frequencies while preserving audio and charging functionality
3Reliability
If switching devices and ESD devices are integrated into USB-C circuit, then device protection and audio capability are improved, but parasitic capacitance increases limiting data transmission rates
Solution Approach 1:
The common mode voltage generator applies preliminary counter-action by proactively establishing stable voltage levels on the differential transmission lines before data transmission occurs. This preemptive voltage stabilization counteracts the capacitive effects of integrated protection devices, preventing signal degradation and enabling high-speed data transmission while maintaining device protection functionality
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
The integrated equalizer significantly reduces insertion loss at higher frequencies, enabling higher data transmission rates and maintaining stable common mode voltage, thus improving data communication efficiency.
Implementation Method 1
the equalizer 316 is configured to apply negative capacitance to the USB differential transmission lines DP/DN to substantially cancel or reduce the parasitic capacitance Cpar associated with the components coupled to the transmission lines DP/DN
Implementation Method 2
the equalizer 316 is configured to apply negative conductance to the USB differential transmission lines DP/DN to substantially cancel or reduce the conductance Gterm due to the driver load resistors RDP/RDN
Data Source
Figure 1~2A
Figure 2B~3
Figure 4A~4B
AI summary
An aspect relates to an apparatus including a first pair of switching devices configured to selectively couple an application processor to a Universal Serial Bus (USB) differential data transmission lines; a USB host port connector coupled to the USB differential data transmission lines; a second pair of switching devices configured to selectively couple an audio circuit to the USB differential data transmission lines; and an equalizer including differential terminals coupled to the USB differential data transmission lines, respectively.