ESD Protection Device Using Bipolar Transistor Snap-Back
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Solution Overview
Problem
Existing ESD protection devices have relatively high clamping voltages, which can damage electronic devices during electrostatic discharge events.
Innovation Solution
Incorporating a bipolar transistor with a base-emitter and base-collector junction connected in anti-series with Zener-diodes, allowing for a voltage snap-back effect that reduces clamping voltage by switching on and decreasing impedance during ESD events, thereby minimizing voltage increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Zener-diodes are used in anti-series connection for ESD protection, then the device can protect against ESD events, but the clamping voltage remains relatively high
Solution Approach 1:
The patent combines Zener-diodes in anti-series connection with a bipolar transistor to form a hybrid ESD protection device. The bipolar transistor is integrated with the diode structure, sharing common regions and forming a unified protection mechanism that leverages both the voltage-clamping特性 of Zener-diodes and the low-impedance current-sinking capability of the bipolar transistor.
Solution Approach 2:
The invention changes the electrical parameters of the protection device by introducing a bipolar transistor with specific current gain β. This transistor enables dynamic parameter adjustment during ESD events, transitioning from high impedance (off state) to low impedance (on state) to reduce clamping voltage from typical Zener-diode levels to significantly lower values during discharge.
2Object-affected harmful factors
If the bipolar transistor impedance decreases rapidly during ESD event, then the clamping voltage is reduced, but the trigger mechanism must be precise to activate at the right voltage level
Solution Approach 1:
The bipolar transistor base-emitter junction provides inherent feedback control for trigger activation. When the voltage across the anti-series Zener-diodes reaches the trigger level, leakage current increases and flows into the base, automatically turning on the transistor. This feedback mechanism ensures precise and consistent trigger voltage without requiring external control circuits.
Solution Approach 2:
The ESD protection device activates itself automatically when the trigger voltage is reached. The increased leakage current during ESD events self-triggers the bipolar transistor through its base current, eliminating the need for external trigger circuits or additional control components. The device serves its own triggering function through its internal structure.
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 achieves a significantly lower clamping voltage, effectively protecting electronic devices from ESD by rapidly reducing impedance and managing ESD current through the bipolar transistor, enhancing the robustness and efficiency of ESD protection.
Implementation Method 1
the bipolar transistor is dimensioned to have such a current gain β that the voltage-current characteristic of the ESD protection device, measured between the first and second contact, exhibits a voltage snap-back effect at its trigger voltage
Implementation Method 2
the first diode and the second diode are Zener-diodes. Zener-diodes are used to clamp in their reverse-direction which advantageously provides clamping at a larger voltage than normal diodes
Data Source
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AI summary
The invention relates to an ESD protection device comprising: a first contact (10) and a second contact (20), and an electrical node (12); a bipolar transistor (6) having a base, an emitter, and a collector, the base and emitter forming a base-emitter junction, the base and collector forming a base-collector junction, the emitter being connected to the first contact (10), the collector being connected to the second contact (20), the base being connect to the electrical node (12); a first diode (1) connected between the electrical node (12) and the first contact (10), the first diode (1) comprising a first junction arranged in the same direction as the base-emitter junction, and - a second diode (2) connected between the electrical node (12) and the second contact (20), in anti-series with the first diode (1) on a path from the first contact (10) to the second contact (20), the second diode (2) comprising a second junction arranged in the same direction as the base-collector junction, wherein the bipolar transistor (6) is dimensioned to have such a current gain (ß) that the voltage-current characteristic of the ESD protection device, measured between the first (10) and second contact (20), exhibits a voltage snap-back effect (SNP) at its trigger voltage (Vtrig). The voltage snap-back effect (SNP) results in a lower clamping voltage of the ESD protection device. The invention further relates a semiconductor device and an integrated system in a package comprising said ESD protection device.