Logic Inverter Over-Current Protection Circuit
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Solution Overview
Problem
Logic inverters are vulnerable to damage from over-voltage and over-current conditions during installation, particularly due to operator mishandling or electrostatic discharge, which can lead to serious damage to the input/output interface circuitry.
Innovation Solution
The implementation of transistor-based logic output circuitry with over-current protection mechanisms, including a transistor with an input signal line, an output signal line, a power supply line, a pull-up resistor, and a feedback resistor between the source terminal and ground, to prevent excessive current from causing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If logic inverter is used as driver/buffer circuitry to provide additional current driving capability, then the current driving capability is improved, but the vulnerability to over-current and over-voltage damage increases
Solution Approach 1:
The feedback resistor is pre-configured between the source terminal and ground to establish a current limit before excessive current can occur. This preliminary protective measure ensures that when over-current conditions arise during installation or operation, the current is automatically clamped to safe levels, preventing damage to the transistor while maintaining the inverter's current driving capability.
Solution Approach 2:
The feedback resistor acts as an intermediary protective element between the power supply and the transistor. It mediates the current flow by providing a parallel path for excessive current, thereby limiting the current through the transistor without completely blocking the inverter's ability to drive loads. This intermediary component safeguards the transistor while preserving functionality.
2Reliability
If protection mechanisms are added to prevent over-current and over-voltage damage, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The feedback resistor is merged with the existing inverter circuit architecture, sharing the same substrate and integrating seamlessly with the transistor. This combination approach provides over-current protection without requiring separate protection circuits or additional discrete components, thereby minimizing the increase in device complexity while maximizing reliability.
Solution Approach 2:
The feedback resistor serves multiple functions simultaneously: it provides over-current protection by clamping excessive current, establishes a defined output impedance, and works with the pull-up resistor to set the operating point of the transistor. This multi-functionality reduces the need for additional dedicated protection components, keeping the circuit relatively simple while achieving comprehensive protection.
Data Source
AI summary
A logic inverter with over-current protection, according to one embodiment, includes: a transistor, an input signal line coupled to a gate terminal of the transistor or a base region of the transistor, an output signal line coupled to a drain terminal of the transistor or a collector region of the transistor, a power supply line coupled to the drain terminal of the transistor or a collector region of the transistor, a pull up resistor between a power supply and one of: the drain terminal of the transistor and the collector region of the transistor, and a feedback resistor between ground and one of: a source terminal of the transistor and an emitter region of the transistor. Other systems, methods, and computer program products are described in additional embodiments.