Pass Transistor Input Interface for Wide Voltage Range Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional integrated circuits are unable to handle a wide range of input voltage levels, as they can be damaged by high voltage signals from both analog and digital controllers, necessitating a solution to safely receive and process signals across different voltage domains.
Innovation Solution
An integrated circuit design featuring a pass transistor with a high drain-to-source breakdown voltage, coupled with a reference voltage node and clamp circuitry, which linearly transfers or limits input signals to prevent damage, providing a capacitive load and minimizing DC current flow, thus protecting internal circuitry from high voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional integrated circuit is used to receive input signals, then the circuit can be simple in design, but it cannot handle high voltage signals from analog controllers and may be damaged
Solution Approach 1:
A pass transistor is introduced as an intermediary component between the input terminal and internal circuitry. The transistor's drain terminal connects to the input terminal while the source terminal connects to internal nodes, acting as a voltage-limited interface that protects internal circuits from high voltage signals while allowing controlled signal passage.
Solution Approach 2:
The pass transistor operates in different regions (linear region for low voltage signals, saturation region for high voltage signals) based on the input voltage level. This dynamic operation mode change allows the circuit to adaptively handle both low-voltage digital signals and high-voltage analog signals without damage.
2Reliability
If voltage limiting circuitry is added to protect internal circuitry, then damage resistance improves, but device complexity increases
Solution Approach 1:
The pass transistor serves multiple functions simultaneously: it acts as a voltage limiter to protect internal circuitry, a signal amplifier for low-voltage digital signals, and a high-impedance buffer that presents a capacitive load to the input terminal. This multi-functionality reduces the need for separate protection circuits.
Solution Approach 2:
The voltage protection function is merged with the signal transmission function in a single pass transistor component. Rather than adding separate protection circuitry, the transistor's inherent voltage-limiting characteristics are utilized to provide both protection and signal handling in one element.
3Loss of information
If the pass transistor presents a low impedance load to the input terminal, then signal transfer is improved, but DC current consumption increases
Solution Approach 1:
The pass transistor dynamically adjusts its output impedance based on the input signal voltage level. For low-voltage digital signals, the transistor operates in the linear region providing low impedance for excellent signal transfer. For high-voltage analog signals, it operates in saturation providing high impedance that minimizes DC current draw while still passing the signal.
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 solution effectively limits voltage levels to safe ranges, reducing the risk of damage to internal circuitry, minimizing power consumption, and reducing the bill of materials by eliminating the need for substantial external components, while maintaining low distortion and negligible DC current draw.
Implementation Method 1
The pass transistor is configured to linearly transfer the input signal to the first node in response to a voltage level of the input signal being below a first voltage level
Implementation Method 2
configured to transfer a voltage-limited version of the input signal to the first node in response to the voltage level being above the first voltage level
Implementation Method 3
The pass transistor may provide a capacitive load to the input terminal. In operation, at most, a negligible DC current flows through the input terminal into the second terminal
Data Source
AI summary
An integrated circuit includes an input terminal configured to receive an input signal, a reference voltage node configured to provide a control voltage, and a pass transistor comprising a first terminal coupled to a first node, a control terminal coupled to the reference voltage node, and a second terminal coupled to the input terminal. The control voltage has a control voltage level sufficient to allow a signal to pass from the second terminal to the first terminal. The pass transistor is configured to linearly transfer the input signal to the first node in response to a voltage level of the input signal being below a first voltage level and configured to transfer a voltage-limited version of the input signal to the first node in response to the voltage level being above the first voltage level. At most, a negligible DC current flows through the input terminal into the second terminal.