AMEYA360:Surge Suppression Circuits-Ameya360电子元器件采购网

AMEYA360:Surge Suppression Circuits

发布时间：2023-04-17 13:25

作者：AMEYA360

来源：网络

阅读量：2097

　　In the previous article we briefly explained surges that occur in gate-source voltages. From this article, AMEYA360 will address measures to deal with surge occurrences. We begin by presenting surge suppression circuits.

AMEYA360:Surge Suppression Circuits

　　Surge Suppression Circuits

　　As explained in the previous article, positive surges in the gate-source voltage (VGS) occur on both switching and non-switching sides, but surges are especially problematic when they occur on the non-switching side (HS: high side) during LS (low side) turn-on (phenomena II). The waveform diagram on the right is the same as one presented in the previous article.

　　The reason for this is that, because the switching side is already in the turned-on state, if a positive voltage surge on the non-switching side has exceeded the gate threshold voltage (VGS(th)) of the SiC MOSFET, simultaneous HS and LS turn-on occurs, and a shoot-through current flows.

　　However, the transconductance of SiC MOSFETs is at least an order of magnitude lower than that of Si-based MOSFETs, and so sudden excessive shoot-through currents do not flow. Consequently, even if a shoot-through current had been flowing, cooling performance is sufficient, and if the Tj(max) of the MOSFET is not exceeded, there should essentially be no problems. Even so, shoot-through currents are factors directly detracting from the efficiency of the system as a whole, and cannot be called a desirable state of affairs. Hence a circuit should be added in order to suppress any voltage surges so that insofar as possible they do not exceed the VGS(th) of an SiC MOSFET.

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Trade news

AMEYA360:ASML Ban Affects China’s Advancement in Chips

　　As part of an agreement between the U.S. government, the Netherlands, and Japan, ASML, Nikon, and Tokyo Electron won’t be supplying their high-end photolithography equipment to Chinese companies.　　According to the Wall Street Journal, “the Netherlands will bar ASML Holding NV, a Dutch maker of photolithography machines, from selling to China at least some immersion lithography machines, the most advanced kind of gear in the company’s deep ultraviolet lithography line.”　　ASML manufactures all of the world’s extreme ultraviolet lithography machines, which are critical for producing cutting-edge semiconductors.　　China could easily circumvent the export bans for advanced semiconductors, as it has been doing for many years. Acquiring huge lithography machines is much more difficult, and making them from scratch is nearly impossible. Furthermore, only a few hundred of those machines are sold every year, making it much easier to control their destination.　　ASML bans chip making equipment to China　　It is unknown how much of that critical equipment has already been sold to China and what capacity Chinese companies already have to produce the most advanced semiconductors.　　While China is unlikely to have the technology to produce sub-10nm chips, it is already investing in new fabs. Currently, only Taiwan’s TSMC can produce 5nm technology. To do that, it requires the advanced lithography machines that ASML has.　　Lithography in the U.S.　　A lithography system is a projection system. Light is projected through a blueprint of the pattern to print (known as a ‘mask’ or ‘reticle’). This process will be repeated 100 times or more, laying patterns on top of patterns to make a complete microchip.　　This crucial technology was discovered in 1957 by Jay Lathrop and James Nall, of the U.S. Army’s Diamond Ordnance Fuse Laboratories in Maryland. They patented the photolithographic techniques used to deposit thin-film metal strips about 200 micrometers wide to connect discrete transistors on a ceramic substrate.　　In 1959 Lathrop joined Texas Instruments, and Nall went to Fairchild Semiconductor. In 1958, engineers at Fairchild built one of the first “step-and-repeat” cameras to easily copy and multiply transistors on a single wafer using photolithography.　　In the early 1980s, GCA Corp. was considered the worldwide leader in photolithography and celebrated as one of the “hottest high-technology companies.” They invented the wafer stepper (the step-and-repeat camera), a device similar to a slide projector or a photographic enlarger, enabling further reductions in chip size. It was the first technology to exceed the 1-micron limit.　　At the time, Japanese competitors Nikon and Canon were catching up quickly and making bold technological investments. While American lithography companies were holding back in capital expenditures until they had a deal with semiconductor manufacturers, the Japanese worked hand-in-hand with them to define roadmaps and coordinate the delivery of new equipment.　　“It was impossible to make semiconductors without lithography tools, but the only remaining U.S. producers were struggling to survive,” wrote Chris Miller in Chip War: The Fight for the World’s Most Critical Technology.　　In 1993, after receiving at least $60 million in funds from the government-backed Sematech consortium, GCA closed its factory in Massachusetts as it could not compete with ASML, Nikon, and Canon.　　ASML can’t meet demand　　While other lithography manufacturers can print 10nm patterns, ASML’s EUV (extreme ultraviolet) technology enables the scale of the smallest feature to be reduced below that limit. That’s why they hold 100 percent of the market for the most advanced lithography machines.ASML Ban Affects China’s Advancement in Chips　　Recently, ASML reported revenues of $23 billion and $6.05 billion in net income for FY2022. The Dutch company sold 317 new and 28 used lithography systems to their customers. They expect an increase of 25 percent in net sales for FY2023.　　“For 2023, ASML expects continued strong growth with a net sales increase of more than 25 percent and a slight improvement in gross margin, relative to 2022. We expect first-quarter net sales between €6.1 billion and €6.5 billion with a gross margin between 49 percent and 50 percent,” said ASML President and CEO Peter Wennink.　　The new restrictions on exporting equipment to China won’t hurt the company’s bottom line, as the demand from Taiwan, Europe, and the U.S. will continue to grow.　　China might retaliate　　Chip-making equipment is critical for China’s ambitions to lead in artificial intelligence and quantum computing technologies.　　While it would be possible for large Chinese companies to source state-of-the-art chips and build new systems abroad, not being able to design and manufacture advanced semiconductors in mainland China is a step back in their ambitions.　　The Chinese government has not issued any comment yet on the new restrictions, but it will likely react. One possibility is trade restrictions on Western businesses.

2023-05-11 11:05 阅读量：2965

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