Stacked PNP Bipolar Transistor ESD Protection Circuit
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Solution Overview
Problem
Existing ESD protection devices often have high trigger voltages, slow reaction times, and temperature-dependent snapback holding voltages, making them inadequate for protecting high voltage core circuits and maintaining stability across a wide temperature range.
Innovation Solution
The ESD protection device employs stacked PNP bipolar transistors and an NMOS transistor, where the emitter and base of the second PNP transistor are connected to the collector of the first PNP transistor, and the gate terminal of the NMOS transistor is connected to the source terminal, forming a parasitic NPN bipolar transistor to quickly shunt ESD current, reducing trigger voltage and snapback holding voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional ESD protection devices are used, then they can provide basic ESD protection, but they have high trigger voltages and slow reaction times
Solution Approach 1:
The ESD protection device is segmented into multiple functional components: a first PNP bipolar transistor for voltage triggering, a second PNP bipolar transistor for current amplification, and an NMOS transistor for rapid current shunting. This segmentation allows each component to perform its specialized function optimally, achieving both fast reaction time and reliable protection.
Solution Approach 2:
The stacked PNP bipolar transistors act as intermediary triggering mechanisms that sense the ESD pulse and activate the NMOS transistor. This intermediary structure enables the system to detect ESD events at lower voltages and trigger the main protection mechanism faster, improving both reaction time and effectiveness.
2Stability of the object's composition
If conventional ESD protection devices are used, then they can shunt ESD current, but they have temperature-dependent snapback holding voltages
Solution Approach 1:
The patent utilizes the temperature-dependent characteristics of bipolar transistors to compensate for temperature variations. The stacked PNP bipolar transistors are configured such that their combined voltage characteristics remain relatively stable across temperature ranges, providing temperature-compensated snapback holding voltage.
Solution Approach 2:
The ESD protection device employs a composite transistor structure combining PNP bipolar transistors and NMOS transistor. This composite configuration leverages the complementary temperature characteristics of different transistor types to achieve temperature-stable operation across a wide temperature range.
3Speed
If the trigger voltage is reduced, then the ESD reaction time improves, but the device may activate at lower voltages than desired
Solution Approach 1:
The patent adds a voltage amplification dimension by stacking two PNP bipolar transistors in series. This allows the triggering mechanism to operate at lower voltages (faster response) while the combined voltage gain of the stacked transistors ensures that the NMOS transistor activates at the desired threshold voltage, maintaining reliable trigger control.
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 configuration allows for effective protection of high voltage core circuits with faster ESD reaction times and stable performance across a wide temperature range, reducing the risk of thermal damage and latch-up issues.
Implementation Method 1
Electrostatic discharge is a sudden flow of electricity that can be caused by a buildup of static electricity. An ESD protection device can be used to shunt ESD current to prevent thermal damage in a device.
Implementation Method 2
stacked first and second PNP bipolar transistors that are configured to shunt current between a first node and a second node in response to an ESD pulse
Data Source
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AI summary
Embodiments of an electrostatic discharge (ESD) protection device and a method for operating an ESD protection device are described. In one embodiment, an ESD protection device includes stacked first and second PNP bipolar transistors that are configured to shunt current between a first node and a second node in response to an ESD pulse received between the first and second nodes and an NMOS transistor connected in series with the stacked first and second PNP bipolar transistors and the second node. An emitter and a base of the second PNP bipolar transistor are connected to a collector of the first PNP bipolar transistor. A gate terminal of the NMOS transistor is connected to a source terminal of the NMOS transistor. Other embodiments are also described.