SCR ESD Protection Shunt Path and Trigger Circuit
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Solution Overview
Problem
Conventional high voltage ESD protection circuits require substantial silicon area and are inefficient due to the need for multiple stacked NPN transistor clamps, which are prone to false triggering and dynamic turn-on caused by parasitic capacitance, making them unsuitable for effective electrostatic discharge protection in high voltage applications.
Innovation Solution
A silicon-controlled rectifier (SCR) based ESD protection device with a shunt path and threshold trigger circuit, where the shunt path is enabled by a power signal to allow displacement current to bypass parasitic capacitance, and the threshold trigger circuit controls the SCR to clamp voltages below its breakdown voltage, reducing false triggering and enhancing sensitivity to real ESD events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple stacked NPN transistor clamps are used for high voltage ESD protection, then the protection capability is improved, but the silicon area consumption increases substantially
Solution Approach 1:
The patent combines multiple ESD protection functions into a single SCR-based clamp circuit. The SCR structure integrates the voltage clamping, current handling, and protection functions that previously required multiple separate NPN transistor clamps, thereby reducing silicon area while maintaining protection capability.
Solution Approach 2:
The patent changes the fundamental operating parameters by transitioning from NPN transistor-based clamping to SCR-based clamping. This parameter change enables higher voltage handling capability and lower area consumption due to the SCR's inherent high-voltage breakdown characteristics and more efficient current conduction path.
2Device complexity
If conventional NPN transistor clamps are used, then the circuit structure is simple, but false triggering occurs due to parasitic capacitance
Solution Approach 1:
The patent introduces a specialized trigger circuit as an intermediary between the parasitic capacitance effects and the main clamp operation. This trigger circuit selectively activates the SCR only when genuine ESD events occur, filtering out false triggering caused by normal circuit operations while maintaining responsiveness to actual ESD threats.
3Speed
If the SCR is designed to be highly sensitive to ESD events, then the protection responsiveness is improved, but false triggering increases
Solution Approach 1:
The patent implements a feedback mechanism through the SCR's regenerative latching action. Once the SCR is triggered by a genuine ESD event, the feedback loop maintains the low-impedance clamping state, ensuring sustained protection. The feedback also helps distinguish between transient noise and actual ESD events, reducing false triggering while maintaining high responsiveness.
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 SCR-based ESD protection device significantly reduces silicon area requirements while maintaining or exceeding the performance of conventional ESD clamps, being less prone to false triggering and more responsive to actual ESD events, thus providing effective protection with improved electrical clamping characteristics.
Implementation Method 1
a breakdown voltage applied between the anode and the cathode
Implementation Method 2
a parasitic capacitance between the gate and an internal node of the silicon-controlled rectifier
Data Source
AI summary
A SCR-based based electrostatic discharge protection device with a shunt path is provided. The shunt path operates at a low resistance when an enabling signal of the shunt path is asserted and a high resistance when the enabling signal is negated. The shunt path connects the cathode and the gate of the silicon-controlled rectifier, and provides a conductive path for displacement current from a parasitic capacitance when the shunt path is enabled, such as when power is provided to the device, and further allows the SCR to enter a low-resistance state when the shunt path is not enabled, such as when power is not provided to the device. A threshold trigger circuit is operably coupled between the anode and the cathode of the silicon-controlled rectifier and is configured to provide a current path when the anode voltage reaches a predetermined value lower than a breakdown voltage of the silicon-controlled rectifier.