ESD Protection Circuit Sequencing NMOS Transistors for Voltage Compatibility
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Solution Overview
Problem
Low-voltage ICs are vulnerable to damage from electrostatic discharge (ESD) when higher voltages are applied, as their existing ESD protection circuits are ineffective in managing such scenarios, leading to malfunction.
Innovation Solution
The proposed ESD protection circuit incorporates NMOS and PMOS transistors, along with detection and trigger units, to form a discharge path from power lines or pads to ground, ensuring effective ESD protection even at higher voltages by sequencing the activation of transistors in response to detection signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a low-voltage ESD protection circuit is used in a low-voltage IC, then the IC can operate at low voltage (1.8V), but the protection circuit becomes ineffective when higher voltages (3V, 3.3V) are applied to the pins
Solution Approach 1:
The ESD protection circuit dynamically adjusts its operating state based on the input voltage level. When a higher voltage is detected at the pin, the circuit activates alternative protection paths involving the second NMOS transistor and adjusted biasing conditions, allowing it to effectively protect against ESD events regardless of whether the operating voltage is 1.8V or 3.3V.
Solution Approach 2:
The circuit changes its electrical parameters (threshold voltages, current paths, transistor activation states) in response to the applied voltage level. Detection circuits monitor the voltage and trigger appropriate parameter adjustments in the ESD protection transistors, enabling the same circuit to maintain protection effectiveness across different voltage domains.
2Reliability
If the ESD protection circuit is designed to handle higher voltages, then it can protect pins operating at 3V or 3.3V, but it may cause malfunctions or false operations in low-voltage devices when higher voltage is applied
Solution Approach 1:
Detection circuits and control transistors act as intermediaries between the high-voltage input pin and the low-voltage internal circuitry. These intermediary elements monitor the voltage level and conditionally activate protection paths, preventing direct coupling of high-voltage transients into sensitive low-voltage sections while still providing ESD protection at the pin level.
Solution Approach 2:
The ESD protection circuit is segmented into multiple independent protection paths and stages. Different transistor networks handle different voltage scenarios, allowing the circuit to engage only the appropriate protection level needed for the current operating condition, thereby avoiding over-protection that could cause malfunction in low-voltage mode.
3Reliability
If a complex trigger unit with multiple transistors is used to sequence the activation of protection transistors, then the ESD discharge path can be reliably formed, but the device complexity increases
Solution Approach 1:
Multiple functions (detection, triggering, and protection activation) are merged into a unified circuit architecture where the same transistor network serves both as the detection element and the protection element. This reduces the need for separate trigger units and minimizes the total transistor count while maintaining reliable sequential activation of the discharge path.
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 prevents ESD damage to ICs by creating a reliable discharge path, even when higher voltages are applied, thereby ensuring the normal functioning of low-voltage ICs.
Implementation Method 1
electrostatic discharge (ESD) protection circuit
Implementation Method 2
a discharge path is formed from the power line to the ground via the first and second NMOS transistors
Data Source
AI summary
An electrostatic discharge protection circuit is provided. First NMOS transistor is coupled to a power line. Second NMOS transistor is coupled between the first NMOS transistor and a ground. Detection unit provides a detection signal when an ESD event occurs at the power line. Trigger unit turns on the second NMOS transistor and the first NMOS transistor in sequence in response to the detection signal. Discharge path is formed from the power line to the ground via the first and second NMOS transistors. First PMOS transistor is coupled between the power line and a gate of the second NMOS transistor. Third NMOS transistor is coupled between the ground and the gate of the second NMOS transistor. Second PMOS transistor is coupled between the gates of the first and second NMOS transistors. Third PMOS transistor is coupled between the power line and the first PMOS transistor.