Bi-directional ESD Protection Circuit with Body Snatching
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Solution Overview
Problem
Conventional Grounded Gate NMOS (GGNMOS) ESD protection circuits are prone to noise sensitivity, as they can be disturbed by noise voltages coupled to the second node, which can forward bias the drain-body junction, potentially affecting the integrated circuit.
Innovation Solution
An ESD protection circuit with a discharging transistor and a body snatching circuit, where the body snatching circuit outputs the lower of the two voltages at the first and second nodes to the body of the discharging transistor, ensuring the drain-body junction remains reverse biased during normal operation and allowing for effective ESD discharge during events, while isolating the circuit from noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the drain-body junction is forward biased to allow noise discharge, then noise can be released, but the integrated circuit becomes susceptible to noise interference
Solution Approach 1:
The body snatching circuit proactively clamps the body voltage to the lower of the two node voltages before noise can forward-bias the drain-body junction. This preliminary voltage clamping action prevents the harmful condition from developing while still allowing ESD protection to function.
Solution Approach 2:
The body snatching circuit acts as an intermediary element between the two nodes and the transistor body. It mediates the voltage relationship by selectively connecting the body to the lower voltage node, thereby controlling the biasing state of the drain-body junction and preventing unwanted noise coupling.
2Adaptability or versatility
If the body voltage follows the second node voltage, then the circuit responds to voltage changes, but noise at the second node disturbs the integrated circuit
Solution Approach 1:
The body snatching circuit preemptively clamps the body voltage to the lower node voltage before noise can couple from the second node to the integrated circuit. This preliminary action ensures the body voltage does not follow noisy variations at the second node while still maintaining proper biasing for ESD protection.
Solution Approach 2:
The body snatching circuit creates a controlled copy of the voltage relationship by selecting the lower voltage node and applying it to the body. This copied voltage reference provides stable biasing without reproducing noise from either node, isolating the integrated circuit from noise while maintaining adaptability.
3Reliability
If a conventional GGNMOS ESD protection circuit is used, then ESD protection is provided, but the circuit is sensitive to noise voltages
Solution Approach 1:
The ESD protection function is segmented into two independent parts: the discharging transistor for ESD protection and the body snatching circuit for noise rejection. This segmentation allows each component to optimize its specific function without compromising the other, achieving both ESD protection and noise immunity.
Solution Approach 2:
The body snatching circuit serves as an intermediary between the external nodes and the transistor body, mediating the voltage relationship to prevent noise coupling. This intermediary structure maintains ESD protection capability while blocking noise paths to the integrated circuit.
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 solution provides bi-directional ESD protection and noise rejection, ensuring the integrated circuit is immune to noise interference, especially in high-current, fast switching applications, and prevents latch-up events.
Implementation Method 1
The body snatching circuit is configured to output the lower one of the first voltage and the second voltage at the output terminal
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
Implementation Method 4
ensuring the drain-body junction remains reverse biased during normal operation and allowing for effective ESD discharge during events, while isolating the circuit from noise
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 of the discharging transistor is electrically coupled to a driving voltage. 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.