USB-C I/O Protection Circuit Using 3.3 V Transistors at 5 V
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Solution Overview
Problem
Conventional USB-C port I/O circuits face challenges in operating and tolerating maximum voltages greater than their rated voltage, particularly 5 V, due to the unavailability of transistors with maximum absolute ratings exceeding 5 V, which limits their functionality and reliability.
Innovation Solution
A circuit design that uses transistors with maximum absolute ratings lower than 5 V, employing a protection circuit with a cascode configuration to generate voltages that allow the circuit to operate and withstand 5 V, by dividing the terminal voltage in an activated state and capping the voltage in a deactivated state, thus avoiding the need for high-voltage transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage divider circuits are used with transistors rated for maximum voltage, then the circuit can withstand high voltage, but transistors with maximum absolute rating of 5 V or more are not available in certain technological sectors
Solution Approach 1:
The circuit segments the voltage handling function across multiple transistors (first transistor and second transistor in series) with lower individual voltage ratings. Each transistor handles a portion of the total voltage, allowing the circuit to withstand 5 V while using only transistors with 3.3 V ratings. This is achieved by dividing the voltage divider bridge into sections controlled by separate transistors whose combined voltage tolerance exceeds the maximum operating voltage.
Solution Approach 2:
A protection circuit acts as an intermediary between the high-voltage terminal and the low-voltage transistors. This protection circuit includes voltage division means that step-down the terminal voltage before it reaches the transistors, and control means that regulate the transistors' operation based on the divided voltage. This intermediary mechanism allows transistors with lower voltage ratings to safely operate in a high-voltage environment.
2Ease of manufacture
If transistors with maximum absolute rating lower than maximum voltage are used, then manufacturing is easier with available components, but the circuit must use complex protection and voltage division mechanisms
Solution Approach 1:
The protection circuit and voltage division mechanism are merged into a unified structure where the voltage divider bridge and transistor control are integrated. The first and second transistors are coupled in series with resistive elements to form an integrated voltage division and protection system, reducing the need for separate protection components and simplifying the overall circuit architecture despite the sophisticated voltage management requirements.
Solution Approach 2:
The transistors perform multiple functions: they act as switches for the voltage divider, provide voltage protection, and enable the circuit to operate at both rated and maximum voltages. The same transistor structure that divides voltage also protects the circuit, eliminating the need for dedicated protection transistors and reducing overall circuit complexity despite the sophisticated voltage management requirements.
3Adaptability or versatility
If the circuit is designed to be functional at 5 V with activated state current passing capability, then USB-C port I/O requirements are met, but the transistors must handle higher voltage stress
Solution Approach 1:
The protection circuit performs preliminary voltage division before the voltage reaches the transistors. The voltage divider bridge pre-reduces the terminal voltage to safe levels that the 3.3 V-rated transistors can handle, even when the terminal is at 5 V. This preliminary action ensures that transistors never experience voltage stress exceeding their ratings, while still allowing the circuit to comply with USB-C requirements for 5 V operation.
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
Enables the construction of a voltage divider circuit functional at and capable of withstanding 5 V using only transistors with a maximum absolute rating of 3.3 V, ensuring the circuit's functionality and safety without high-voltage transistors, while meeting USB-C port I/O requirements.
Implementation Method 1
the second voltage is obtained by the level of a control voltage minus a threshold voltage of a protection transistor
Data Source
AI summary
Provided is an integrated circuit that includes: a terminal designed to receive a signal at a rated voltage level which can rise to a maximum voltage level; an output circuit including a first transistor and a second transistor coupled in series between the terminal and an output stage; and a protection circuit designed to generate a first voltage controlling the first transistor, and a second voltage controlling the second transistor. In an activated state, the first voltage and the second voltage are obtained by dividing the voltage level of said terminal. In a deactivated state, the first voltage is obtained by the voltage level of said terminal, and the second voltage is obtained by the level of a control voltage minus a threshold voltage of a protection transistor.