The smartbook is an emerging new type of netbook that can be carried around and out of the box like a mobile phone. It has a high probability of being used outdoors, so special design must be made for ESD protection and lightning protection. ESD protection and lightning protection, although they belong to the same category of overvoltage protection, are very different in their design requirements and challenges. In order to give readers clearer guidance on design ideas and solution selection, this magazine specially invited Dr. Jiang Xinqin from the research and development department of Taiwan Jingyan Technology Co., Ltd. to share his design experience. Dr. Jiang has 28 invention patents in this area and is an IEEE recognized circuit protection expert.
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What is the biggest difference in design requirements for ESD protection and lightning protection?
A: The noise generated by lightning strikes is low-frequency (the event length is above 20usec) but the energy is very large. Therefore, the lightning protection component is designed to vent large energy noise, not its reaction speed. The noise generated by the ESD (electrostatic discharge) event is a high frequency (with an event length of less than 60 nsec) but the energy is very small. Therefore, the design of the ESD protection component must focus on the reaction speed, and only the reaction speed is within 10 nsec. The protection component has ESD protection.
What are the main design challenges for these two overvoltage protections?
A: The design challenge of lightning protection components is to reduce the lightning energy of the maximum energy under a limited component volume. The choice of component materials is the design focus. The design challenge of ESD protection components is to design the component's fast response speed and low on-resistance after the reaction. Only in this way can the low clamping voltage be provided to protect the normal operation of the system, and the design focus of such components will be on the components. The structure and the process used.
What is the most reliable or cost-effective component to achieve these two types of overvoltage protection? What issues should be paid attention to in specific engineering design?
A: Lightning protection components are still mainly made of ceramic materials (such as varistor), because of their low cost and can vent large energy lightning noise. However, such components are slow to respond (greater than 35nsec) and cannot be used as ESD protection components at the same time. ESD protection components are now based on components made from semiconductor materials and processes because of their best protection, optimum component reliability, and cost reduction due to the array design. In addition, through proper design, ESD protection components can also be used as lower energy lightning protection components (eg, lightning protection components less than 40A).
In order for a netbook or smartbook to successfully pass the rigorous IEC61000-4-2level-4ESD test or certification, what electronic and mechanical protection measures do you think the system design engineer should take?
A: Due to cost and weight considerations, current system products are forced to use a large number of non-conductive materials to design the mechanism and appearance, which causes the system design engineer to have no mechanical protection measures to design a complete and safe electrostatic discharge. Path to protect the system. At this time, it is necessary to introduce semiconductor-type and array-type ESD protection components, combined with limited mechanical protection measures, to design a minimum impedance electrostatic discharge path for ESD noise to pass, which is like burying a lightning rod in the system product. Same as in the middle.
Which type of ESD protection component should be used to make the USB2.0, USB3.0, HDMI1, 3, DisplayPort, VGA, and 10/100M Ethernet interfaces meet the requirements of IEC61000-4-2Level-4 most economically? What are the minimum key performance indicators that are met separately?
A: First, the Array-type ESD protection component should be used, so that the PCB space can be reduced with a minimum number of components and the parasitic impedance of the PCB can be reduced. Second, the line capacitance of the ESD protection component should be low enough, such as USB2. 0 needs less than 3pF, USB3.0.0 needs less than 0. 3pF, HDMI1. 3 needs less than 0. 6pF, DisplayPort also needs to use less than 0. 6pF, VGA needs less than 2pF, 10/100MLAN needs to use ESD less than 3pF The protection component; third, the clamping voltage of the ESD protection component must be low enough to allow the system to operate undisturbed when ESD occurs. As for the low clamping voltage, it depends on the noise immunity of the system. However, it is still difficult to set the actual value, and the results are not low enough.
What type of ESD protection component should be used to best meet the IEC61000-4-2 Level-4 requirements for the power interface? What is the minimum key performance metric that should be met?
Answer: IEC61000-4-2Level-4 defines that the ESD test voltage value must be 8KV contact and 15KV air discharge. Therefore, the ESD protection component must be able to withstand this level of ESD bombardment without damage. basic requirements. But what really matters is, which one is the product's failure criterion? In the past, Class-C (requires manual reset after ESD bombardment) is enough, but with the improvement of product quality, at least Class is now required. -B (The system will automatically recover from abnormal actions after ESD bombardment). Even worse, Class-A will be required (the system will not observe any abnormal actions after ESD bombardment) as the failure criterion. At this time, it is necessary to use the voltage of the clamping voltage as the basis for selecting the ESD protection component. The lower the clamping voltage, the opportunity to pass the ESD test of the Class-A. Therefore, the key performance indicator of ESD protection components is their low clamping voltage.
What are the main selling points of Jingsheng's ESD and lightning protection components compared to competitors?
A: The selling point of Jingsheng Technology's ESD and lightning protection components is that it has the lowest clamping voltage, and the lowest clamping voltage represents the strongest protection against system operation. Especially for ESD protection components, Crystal Technology is the first strong introduction and recommendation system design engineer to use ESD to clamp the voltage level when selecting the standard. Because, many people will be fascinated by the protection element that can withstand the higher ESDlevel bombardment without damage. It is like using the personal protection. If the insurance is strong, but it is not willing for you. Block the knife and block the bullet, then he has no protection for you. The same is true for ESD protection components. A protection element that can withstand high ESDlevel bombardment without damage. If the ESD clamping voltage is not provided, when ESD bombards the system, it is common for ESD protection components to be safe. But some of the main ICs of the system have been broken.
Would you recommend a system design engineer to choose an ESD protection component with a low ESD clamping voltage?
A: To compare the clamping voltage of two ESD protection components, if you directly use the electrostatic gun to bombard the ESD protection component and then use the oscilloscope to observe it, it is not easy to observe the height, because the oscilloscope will see a lot of high frequency noise. Cover the voltage changes of the two ESD protection components. Therefore, the correct comparison method is to use the TransmissionLinePulsing (TLP) System to indirectly measure the voltage level of the two ESD protection components. Using the TLP amount to an ESD protection component with a lower clamping voltage will provide better protection for the system. Jingyu Technology is the first to introduce this option to system design engineers, and has successfully enabled many system design engineers to select the appropriate ESD protection components in one way, saving ESD design and test time for many systems.
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