SCR Trigger Circuit for Low-Voltage ESD Protection in Data Links
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Solution Overview
Problem
Existing data transmission systems face challenges in effectively dissipating electrostatic discharge (ESD) events, leading to potential component damage due to high trigger voltages and large differences between low-leakage and trigger voltages when using diode strings for ESD protection.
Innovation Solution
A current-controlled semiconductor system comprising a semiconductor controlled rectifier (SCR) device with a current trigger device, such as a resistor-triggered Shockley diode, which reduces trigger voltage and leakage current, achieving low capacitance and simplified configuration without the need for additional trigger diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diode strings are used for external triggering of SCR, then trigger voltage can be reduced, but the difference between low-leakage voltage range and trigger voltage becomes large
Solution Approach 1:
The patent changes the electrical parameters of the triggering mechanism by using an integrated current-controlled triggering circuit instead of passive diode strings. This circuit provides a well-defined trigger voltage that is significantly lower than the low-leakage voltage range, thereby reducing the voltage difference and improving the reliability of ESD protection while maintaining ease of manufacture.
2Reliability
If external triggering with diode strings is implemented, then SCR can be triggered, but no clear breakdown characteristic is obtained
Solution Approach 1:
The patent replaces the passive diode string triggering mechanism with an active current-controlled triggering circuit that provides clear and well-defined breakdown characteristics. This electronic control mechanism enables precise triggering with distinct breakdown points, improving both triggering reliability and measurement precision compared to the exponential current-voltage relationship of diode strings.
3Reliability
If high trigger voltage is used in SCR, then deep snap-back and low clamping voltage are achieved, but component damage risk increases during ESD events
Solution Approach 1:
The patent introduces an integrated current-controlled triggering circuit as an intermediary between the input signal and the SCR triggering mechanism. This intermediary provides precise control over the trigger voltage, enabling the SCR to achieve deep snap-back and low clamping voltage characteristics while preventing excessive trigger voltages that could cause component damage during ESD events.
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 system provides effective ESD protection with low leakage current and trigger voltage, reducing the risk of component damage and eliminating the need for sophisticated isolation schemes, resulting in a more efficient and simplified data transmission system.
Implementation Method 1
Electrostatic discharge is a problem encountered in a range of electronic systems, including data transmission systems. When an ESD event occurs in a data transmission system, components of the data transmission system may be damaged if the discharge is not suitably dissipated by the system.
Implementation Method 2
Semiconductor controlled rectifiers or SCRs are popular for ESD protection due to their deep snap-back and consequently low clamping voltage.
Implementation Method 3
The trigger voltages can be high, especially when a low capacitance is needed for proper operation. For reducing the trigger voltage, a well-known solution implements external triggering, that is using a current source with a low turn-on voltage to forward bias one emitter base junction of the SCR.
Implementation Method 4
at least a first SCR junction element is provided, electrically connected with the second SCR layer and the signal line, and/or a second SCR junction element is provided, electrically connected with the third SCR layer and the ground line
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
According to a first example of the disclosure, a current-controlled semiconductor system is proposed, comprising a signal line for carrying a signal; a ground line for connecting to ground; and a semiconductor controlled rectifier, SCR, device comprising a first SCR layer doped with a first type of charge carriers; a second SCR layer doped with a second type of charge carriers different from the first type of charge carriers; a third SCR layer doped with the first type of charge carriers; a fourth SCR layer doped with the second type of charge carriers; an input terminal electrically connected with the first SCR layer and the signal line as well as an output terminal electrically connected with the fourth SCR layer and the ground line; at least a first SCR junction element electrically connected with the second SCR layer and the signal line, and/or a second SCR junction element electrically connected with the third SCR layer and the ground line, the current-controlled semiconductor system further comprising at least one current trigger device electrically connecting the signal line with the third SCR layer or the ground line with second SCR layer.