Voltage-Mode Transmitter Circuit With Overvoltage Protection
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Solution Overview
Problem
Existing USB transmitter circuits face challenges in implementing data transmission using transistors with lower withstand voltages, especially when dealing with high data signal levels up to 3.3 V.
Innovation Solution
A voltage mode transmitter circuit is designed with an overvoltage protection mechanism, incorporating a low-dropout (LDO) regulator, data processing circuit, pre-emphasis circuit, and voltage protection circuit, all implemented using transistors with lower withstand voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If transistors with lower withstand voltages are used in USB transmitter circuits, then manufacturing cost and device integration are improved, but the circuit cannot handle high data signal levels up to 3.3 V
Solution Approach 1:
The patent introduces a voltage protection circuit as an intermediary component between the high-voltage USB data lines and the low-voltage transistor-based transmitter circuit. This protection circuit includes voltage clamping elements (such as diodes or transistors configured as voltage clamps) that limit the voltage seen by the internal transistors to below their withstand voltage threshold, while still allowing the external interface to handle 3.3V signals. This mediator isolates the vulnerable transistors from harmful overvoltage conditions.
Solution Approach 2:
The patent implements protective structures in advance before the high-voltage signals can damage the transistors. The voltage protection circuit is designed with pre-configured clamping elements that automatically activate when voltage exceeds safe levels, providing cushioning protection before damage occurs. This includes bias voltage generation circuits that prepare protection mechanisms ahead of time.
2Reliability
If voltage protection circuits are added to protect transistors from overvoltage, then transistor reliability is improved, but circuit complexity increases
Solution Approach 1:
The patent merges the voltage protection function with the existing transmitter circuit structures. The protection circuits are integrated into the data processing and pre-emphasis circuits, sharing common transistors and signal paths where possible. For example, certain transistors in the data processing circuit are configured to serve both signal processing and voltage clamping functions, reducing the need for separate dedicated protection components.
Solution Approach 2:
The patent designs circuit elements to perform multiple functions. The same transistor network is used for both data signal processing and overvoltage protection. The bias voltage generation circuit serves both to enable normal circuit operation and to activate protection mechanisms. This multi-functionality reduces the overall component count and circuit complexity despite adding protection capabilities.
Data Source
AI summary
A voltage mode transmitter circuit includes a low-dropout (LDO) regulator and an output circuit. The LDO regulator generates a driving voltage. The output circuit generates an output signal, and includes: a termination resistor, transmitting the output signal; a data processing circuit, driven by the driving voltage and adjusting a level of a node according to first and second data signals; a pre-emphasis circuit, transmitting a supply voltage to the node according to a control signal to adjust a transition edge of the output signal; a voltage protection circuit, providing an overvoltage protection according to a bias voltage, and coupling the node to the termination resistor. The data processing circuit, the pre-emphasis circuit, and the voltage protection circuit include at least one transistor, and a highest level of the output signal is higher than a withstand voltage of the at least one transistor.