ESD Protection Circuit with Sequential NMOS Triggering
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Solution Overview
Problem
Low-voltage integrated circuits (ICs) are unable to protect pins operating at higher voltages due to inadequate electrostatic discharge (ESD) protection, leading to malfunctions when higher voltages are applied to low-voltage devices.
Innovation Solution
An ESD protection circuit comprising NMOS transistors and a detection unit that forms a discharge path from a power line to ground in response to an ESD event, utilizing a trigger unit to sequence the activation of NMOS transistors and providing an effective discharge path to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low-voltage ESD protection circuits are used in low-voltage ICs, then the ICs can operate at lower voltages (1.8V), but the circuits cannot protect pins operating at higher voltages (3V, 3.3V) leading to malfunctions
Solution Approach 1:
The ESD protection circuit dynamically adjusts its operating characteristics based on the applied voltage. The circuit remains in a high-impedance state during normal low-voltage operation but transitions to a low-impedance discharge path when ESD events occur at higher voltages, enabling adaptive protection without sacrificing low-voltage operation
Solution Approach 2:
The circuit changes its electrical parameters (impedance, conductivity) in response to voltage levels and ESD events. By modifying the conduction state of transistors based on detected voltage conditions, the circuit transforms from a non-conductive state during normal operation to a conductive discharge path during ESD events, resolving the contradiction between low-voltage operation and high-voltage protection
2Adaptability or versatility
If higher voltage is applied to low-voltage devices, then pins can operate at higher voltages (3V, 3.3V), but malfunctions occur because the low-voltage ESD protection circuit is unable to protect these pins
Solution Approach 1:
The ESD protection circuit is designed to perform multiple functions: protecting low-voltage internal circuits during normal operation and protecting high-voltage pins during ESD events. The circuit universally handles both low-voltage and high-voltage conditions by dynamically switching its protection mechanism, enabling a single circuit to serve multiple voltage regimes
3Reliability
If a discharge path is formed during ESD events, then ESD damage is prevented, but the circuit must rapidly switch from high-impedance to low-impedance state requiring fast trigger response
Solution Approach 1:
The detection unit continuously monitors voltage conditions and prepares the trigger mechanism in advance. When ESD voltage thresholds are detected, the trigger unit is already primed to immediately activate the discharge path, reducing response time by having the protection mechanism ready before the actual ESD event occurs
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 prevents ESD damage to ICs by creating a reliable discharge path from higher voltage pins to ground, ensuring the normal functioning of low-voltage devices even when exposed to higher operating voltages.
Implementation Method 1
a discharge path is formed from the power line to the ground via the first and second NMOS transistors
Implementation Method 2
a detection unit, providing a detection signal when an ESD event occurs at the power line
Data Source
AI summary
An electrostatic discharge (ESD) protection circuit is provided. The ESD protection circuit includes a first NMOS transistor coupled to a power line, a second NMOS transistor coupled between the first transistor and a ground, a detection unit, providing a detection signal when an ESD event occurs at the power line, and a trigger unit, turning on the second NMOS transistor and the first NMOS transistor in sequence in response to the detection signal, such that a discharge path is formed from the power line to the ground via the first and second NMOS transistors. The trigger unit includes a first PMOS transistor coupled between the power line and a gate of the second NMOS transistor, a fourth resistor, and a second PMOS transistor, having a gate coupled to the cathode of the diode for receiving the detection signal.