Bi-Directional ESD Protection Circuit Using Single PN Junction
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Solution Overview
Problem
The miniaturization of transistors and circuits in semiconductor substrates makes them increasingly susceptible to damage from electrostatic discharge (ESD) events, and existing ESD protection circuits, such as dual-diode structures, impose significant capacitive loads on pins, particularly in high-speed analog circuits, which can reduce performance and consume substantial area.
Innovation Solution
The implementation of a bi-directional ESD protection circuit using a silicon-controlled rectifier (SCR) and a diode sharing a single PN junction, along with a floating P-well contact, reduces capacitive load on pins and allows for efficient ESD protection without the need for connections to both VDD and VSS rails, thereby minimizing the impact on high-speed circuit performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual-diode ESD protection structures are used, then ESD protection capability is improved, but capacitive load on pins increases and performance of high-speed circuits deteriorates
Solution Approach 1:
The patent merges the ESD protection function with the existing circuit structure by using the body diode of the driver/receiver transistor itself as part of the protection mechanism, rather than adding separate protection diodes. This integration eliminates the need for additional external capacitive elements while maintaining ESD protection capability.
Solution Approach 2:
The driver/receiver transistor is designed to serve multiple functions: normal signal driving/receiving and ESD protection. The transistor's inherent body diode and controlled conduction paths provide protection functionality without requiring dedicated protection components, reducing overall capacitive load on the pin.
2Reliability
If dual-diode ESD protection structures are used, then ESD protection capability is improved, but area consumption increases
Solution Approach 1:
The protection circuit functionality is merged into the existing driver/receiver transistor structure, eliminating the need for separate protection diode components and their associated layout area. The same transistor that performs signal functions also provides ESD protection through its inherent characteristics.
Solution Approach 2:
The driver/receiver transistor performs dual roles as both a signal processing element and an ESD protection element, maximizing the utility of existing circuit components and avoiding additional area consumption for dedicated protection structures.
3Reliability
If ESD protection circuits are designed to withstand maximum ESD currents/voltages, then protection capability is improved, but device size and complexity increase
Solution Approach 1:
The driver/receiver transistor uses its own inherent body diode and conduction characteristics to provide ESD protection, eliminating the need for complex external protection circuitry. The transistor's natural electrical properties are leveraged to handle ESD events without additional control logic or components.
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 solution effectively mitigates the risk of ESD damage while maintaining high-speed circuit performance by reducing capacitive load and area consumption, making it suitable for sensitive pins like PCIe and USB interfaces.
Implementation Method 1
A sudden discharge of the static charge can cause high currents and voltages that can damage the integrated circuit
Implementation Method 2
an SCR and a diode sharing a PN junction and forming a bi-directional ESD circuit
Data Source
AI summary
In an embodiment, an ESD protection circuit may include a silicon-controlled rectifier (SCR) and a diode sharing a PN junction and forming a bi-directional ESD circuit. The single PN junction may reduce the capacitive load on the pin, which may allow the high speed circuit to meet its performance goals. In an embodiment, a floating P-well contact may be placed between two neighboring SCRs, to control triggering of the SCRs.