ESD Protection Circuit With Isolated Transistor and Diode Structures
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Solution Overview
Problem
Conventional ESD protection schemes for electronic devices often compromise performance by allowing parasitic silicon-controlled rectifier (SCR) action, which can damage devices during electrostatic discharge events, especially in high-frequency applications like radar and satellite communications.
Innovation Solution
The implementation of an ESD protection circuit using isolated transistor and diode structures, specifically a five-electrode isolated N-channel MOS transistor and isolated P-N junction diodes, which eliminate parasitic SCR action by utilizing deep trench isolation to isolate components and prevent unintended thyristor triggering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ESD protection schemes are used, then ESD protection is provided, but parasitic SCR action occurs which damages devices during ESD events
Solution Approach 1:
The ESD protection circuit is divided into separate functional blocks: an ESD protection transistor (first circuit block) and ESD protection diodes (second circuit block), which are physically isolated from each other using deep trench isolation. This segmentation prevents the parasitic SCR action that would occur if these components were connected, as the isolation structure breaks the feedback path required for SCR triggering while maintaining effective ESD protection through each component's individual operation.
2Reliability
If ESD protection schemes are implemented, then device protection is achieved, but performance of nonstandard inputs and outputs is impacted
Solution Approach 1:
By segmenting the ESD protection into isolated transistor and diode circuits, each component can be independently optimized for its specific function without interfering with signal paths. The isolated structure prevents unwanted interactions and parasitic effects that would otherwise degrade the performance of nonstandard I/O operations, while still providing comprehensive protection.
Solution Approach 2:
The deep trench isolation structure acts as an intermediary that physically separates the ESD protection transistor from the ESD protection diodes. This isolation structure serves as a mediator that prevents harmful electrical interactions between the two circuit blocks while allowing both to function effectively in protecting the device without impacting normal and nonstandard I/O performance.
3Object-affected harmful factors
If isolated transistor and diode structures are used, then parasitic SCR action is eliminated, but device complexity increases
Solution Approach 1:
While segmentation into isolated components does increase structural complexity, it eliminates the parasitic SCR action that would otherwise require complex protection mechanisms. The deep trench isolation provides a clean, well-defined separation that simplifies the overall design by preventing unpredictable parasitic effects, making the circuit behavior more predictable and easier to analyze despite the additional isolation structures.
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
This approach provides robust ESD protection by preventing parasitic SCR action, ensuring device integrity during ESD events while maintaining performance for negative voltage signals up to 30 GHz, thus enhancing the reliability of electronic devices in harsh environments.
Implementation Method 1
utilizing isolated transistor and diode structures which eliminate parasitic silicon-controlled rectifier (SCR) action associated with other ESD protection techniques
Data Source
AI summary
An electrostatic-discharge (ESD) protection circuit is provided. The circuit includes an I/O terminal coupled for receiving a signal having a negative voltage relative to a voltage supply terminal. An ESD transistor is formed in an isolated well. The transistor includes a control electrode and a first current electrode coupled to the I/O terminal. The isolated well is configured as a body electrode of the transistor. An ESD diode includes an anode electrode coupled to the voltage supply terminal and a cathode electrode coupled to a second current electrode of the transistor.