Bi-directional Snapback ESD Protection Circuit with Body Snatching
Solution Overview
Problem
Conventional Grounded Gate NMOS (GGNMOS) ESD protection circuits are prone to noise sensitivity due to forward biasing of the drain-body junction, which can disturb integrated circuits when noise voltage exceeds the forward on-threshold voltage, leading to potential damage from electrostatic discharge (ESD) events.
Innovation Solution
An ESD protection circuit with a discharging transistor and a body snatching circuit, where the body snatching circuit determines whether to output the voltage from the first node or the second node based on which has a lower value, ensuring the drain-body junction remains reverse biased during normal operation and can conduct current during ESD events, while isolating nodes to prevent noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the drain-body junction is reverse biased to block noise, then noise sensitivity is reduced, but ESD protection capability is weakened
Solution Approach 1:
The body snatching circuit serves as an intermediary that dynamically adjusts the body voltage to switch between reverse-bias (for noise blocking) and forward-bias (for ESD conduction) states. This mediator enables the system to achieve both low noise sensitivity during normal operation and high ESD protection capability during electrostatic events
Solution Approach 2:
The invention changes the voltage parameter of the body terminal dynamically. By adjusting the body voltage from a reverse-biased state (providing noise immunity) to a forward-biased state (providing ESD conduction path), the system can switch between protecting against noise and protecting against ESD, resolving the contradiction between these two protective functions
2Reliability
If conventional GGNMOS architecture is used for ESD protection, then ESD discharge capability is improved, but noise sensitivity increases
Solution Approach 1:
The patent segments the ESD protection function from the normal operation function by introducing a separate body snatching circuit that independently controls the body voltage. This segmentation allows the drain-body junction to serve dual purposes: ESD conduction path when needed, and noise-blocking barrier during normal operation, resolving the contradiction inherent in the conventional unified GGNMOS structure
Solution Approach 2:
The body snatching circuit acts as an intermediary control mechanism that decouples the relationship between ESD protection and noise sensitivity. By mediating the body voltage, it enables the NMOS transistor to provide robust ESD protection while maintaining low noise sensitivity during normal operation, overcoming the limitation of conventional GGNMOS architecture
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 proposed ESD protection circuit effectively discharges ESD energy and isolates noise, providing bi-directional protection to integrated circuits from ESD damage while rejecting noise, especially in high-current, fast-switching applications, thus ensuring the integrated circuit operates normally.
Implementation Method 1
The body snatching circuit is configured to output either the first voltage or the second voltage at the output terminal, based on which of the first voltage and the second voltage has a lower value
Implementation Method 2
the parasitic bipolar transistor formed by the drain, the body and the source of the NMOS transistor is turned on and conducts current from the first node to the second node to discharge ESD energy, due to the reverse junction breakdown and secondary breakdown of the parasitic bipolar transistor
Implementation Method 3
the parasitic bipolar transistor formed by the drain, the body and the source of the NMOS transistor is turned on and conducts current from the first node to the second node to discharge ESD energy, due to the reverse junction breakdown and secondary breakdown of the parasitic bipolar transistor, which is observed as a snapback behavior
Implementation Method 4
ensuring the drain-body junction remains reverse biased during normal operation and can conduct current during ESD events, while isolating nodes to prevent noise interference
Data Source
AI summary
An ESD protection circuit having a discharging transistor and a body snatching circuit. The discharging transistor is electrically coupled between a first node and a second node. The gate and the body of the discharging transistor are electrically coupled together. The body snatching circuit receives the voltages at the first and second nodes and outputs either the voltage at the first node or the voltage at the second node based on which of these two voltages have a lower value. The output voltage of the body snatching circuit is provided to the body of the discharging transistor.