Lots of great information came out of the two days of workshops in Japan recently organized by the SOI Consortium. Some of the presentations are now posted on the consortium website (get them here).
The first day (held in Yokohama and sponsored by Silvaco) focused on FD-SOI and RF-SOI design. The second day (held at U. Tokyo) focused on More than Moore (especially silicon photonics, MEMS & sensors), and the SOI manufacturing ecosystem.
The 1st day panel discussion was so interesting we’ll give it a post of its own, then follow up with round-ups of the presentations from both days.
The morning panel discussion on end-user deployment for FD and RF-SOI was moderated by SOI Consortium Executive Director Giorgio Cesana. GF’s CTO Subi Kengeri led off saying that that 2017 had been the year of FD-SOI adoption. Samsung Director Adam Lee noted that in the beginning nobody believed it would get traction, but now everybody does, and Samsung is commercializing it: chips coming out this year will ramp in volume in 2019.
VeriSilicon CEO Wayne Dai said he sees great potential in IoT, where the volumes are high but fragmented. In IoT, he said, you need RF, but you really only need very high performance about 20% of the time, which is a perfect fit for FD-SOI.
ST Director John Carey noted that ST’s been using FD-SOI since 2014. They’ve fabbed products for cryptocurrency and infrastructure. Now in their second and third generations of designing with it, they’ve got some big FD-SOI chips coming out next year with embedded memory and RF. He sees it being particularly successful in mmWave, automotive and IoT.
The conversation then shifted to RF-SOI. Mostofa Emam, CEO of Incize, explained that since RF-SOI is already in every smart phone, it’s in a different situation from FD-SOI. The emphasis here is now on adding more blocks. “RF is an art,” he said. “It takes an artist. You need talented artists and tools.” One of the biggest challenges for fabs that are newcomers is models – not just at the transistor level, but also at the substrate level. The big players have addressed this, but Incize is working to support more foundries with new, innovative approaches, and helping them develop robust PDKs. The industry needs more good RF designers as well as better RF design flow, he concluded.
Coming back to FD-SOI, Cesana asked about non-volatile memory (NVM). Samsung’s Lee said they’ve already got NVM options including eMRAM for 28nm, and customers are now requesting eMRAM PDKs for the next node (18FDS). ST’s Kengeri added eNVM is important for FD-SOI, especially since flash is not scaling. While there are lots of options, MRAM gives you all the value, and in FD-SOI it only adds three more mask steps, so cost savings are maintained.
With respect to local computing for AI with FD-SOI, everyone agreed on the importance of the edge. In addition to RF, FD-SOI gives you density even at 28nm, explained Carey. You can manually control power with back biasing, so you get something very flexible, especially for NB-IoT applications where the battery will have to last for 10 years. In fact Kengeri sees FD-SOI as enabling fog/edge computing.
The next question was about 5G: which applications would we be seeing first, and how does FD-SOI help? Lee said Samsung’s seeing it for apps up to 10GHz as well as mmWave. Customers are telling them they want FD-SOI for technical reasons.
Kengeri expanded on that point, saying it comes down to fundamental physics: gate resistance, capacitance, mismatch. FD-SOI has lower Vmin and better Fmax compared to FinFETs, and that’s what tier-one players want.
Carey brought it back to RF-SOI (noting that ST’s introducing a 45nm version), which supports a large number of elements and increased complexity with smaller power budgets. Emam then asked the foundry guys about mmWave. Substrates won’t be the bottleneck he said, so what’s the FD-SOI/mmWave roadmap? Kengeri responded that GF’s ready. Lee said Samsung is also ready, and you’d see it next year on handsets. Samsung has engaged with customers on 30GHz for the middle of next year, he added: it’s qualified. Carey said ST sees it first in consumer premises equipment that’s connected by satellite.
Cesana then asked about image sensor processors (ISPs), noting that analyst Handel Jones has said this is a big opportunity for FD-SOI. You can do 3D integration with sensors, but heat makes noise, so you need technology that decreases heat production and doesn’t give you hotspots (which would be visible in the image). Kengeri pointed to challenges in power density, thermal envelopes and the RTS (random telegraph noise signal). Although there are a lot of options, FD-SOI plays well for thermals and noise, so GF sees a good opportunity here. Dai added that the industry needs volume applications for FD-SOI, and ISPs need to bring more logic closer to the camera. And he concurred that you need FD-SOI for the thermals: it’s very important.
In closing, Dai noted that as a design house, “We walk on two legs: FinFETs and FD-SOI.” 28, 22, 18 and 12nm FD-SOI all enable differentiation. In particular, you need something between 20nm and 7nm: FD-SOI is here. Asked about Japan in particular, Dai said beyond automotive he saw lots of potential in ULP for AVR. Kengeri added that for any applications besides performance-at-any-cost, FD-SOI is the right enabler.
Since about a third of all IoT devices are expected to be connected by Bluetooth, chip designers need IP solutions that will help reduce system cost and greatly improve battery life. And that’s just what VeriSilicon has announced for GlobalFoundries’ 22FDX® (FD-SOI) process.
“By taking advantage of integrated RF capabilities of FD-SOI, in particular GF’s 22FDX, our BLE 5.0 RF IP will significantly reduce the system cost and greatly boost the growth momentum of wearable products such as wireless earplugs,” said Dr. Wayne Dai, Founder, Chairman, President and CEO of VeriSilicon. 22FDX enables efficient single-chip integration of RF, transceiver, baseband, processor, and power management components. GF and VeriSilicon are working on an SoC using VeriSilicon’s BLE 5.0 RF IP in GF’s 22FDX process.
The latest iteration of Bluetooth is 5, which (like its predecessor 4) has a Low Energy (LE) RF option – but with big improvements. According to the Bluetooth website, “With 4x range, 2x speed and 8x broadcasting message capacity, the enhancements of Bluetooth 5 focus on increasing the functionality of Bluetooth for the IoT.” BLE 5.0 was designed for very low power operation and is optimized for the sorts of short burst data transmissions you’ll get with IoT.
On the strength of VeriSilicon’s innovative RF architecture and by leveraging GF’s 22FDX technology, VeriSilicon says the new IP product achieves significant improvements in power, area, and cost compared to current offerings, so it will better serve the emerging and increasing wearable devices and IoT applications space.
“VeriSilicon’s BLE IP complements GF’s 22FDX FD-SOI capabilities and is well positioned to support the explosive growth of low-power IoT and connected devices,” said Mark Ireland, vice president of ecosystem partnerships at GF. “Together, we broaden our IP and services to further enable our mutual clients to provide power and cost efficient solutions.”
VeriSilicon BLE 5.0 RF IP includes a transceiver that is compliant with the BLE 5.0 specification and supports GFSK modulation and demodulation. The silicon measurement shows that the sensitivity can be tested up to -98dBm with less than 7mW power dissipation in typical conditions. It largely improves battery life for low power IoT applications. In addition, the RF transceiver saves 40% area compared to a similar implementation on 55nm bulk CMOS. Besides the RF transceiver, this IP integrates on-chip balun, TX/RX switch and 32K RC OSC driver to save the BOM. Moreover, high efficiency DC/DC and LDOs are also available for power management.
Some great pieces of FD-SOI news from QuickLogic. The company recently demonstrated its ultra-low power ArcticPro™ embedded FPGA (eFPGA) solutions at the GlobalFoundries Technology Conferences in Santa Clara, California, Munich and Shanghai. The technology is available now.
ArcticPro is the industry’s ﬁrst eFPGA offering for GF’s 22FDX® process (btw they’ve been shipping it in volume for GF’s 65nm and 40nm bulk processes for years). The company says its ultra-low power eFPGA architecture and mature software offer semiconductor and system companies the ability to integrate programmable hardware accelerators to lower power consumption and the flexibility to reconfigure a device’s functionality in the field.
QuickLogic has also announced that the technical university ETH Zurich will integrate QuickLogic’s ArcticPro technology onto the university’s PULP platform. PULP is a silicon-proven open-source parallel platform for ultra-low power computing created with the objective of delivering high compute bandwidth combined with high-energy efficiency. ETH will become the first licensee of eFPGA technology from QuickLogic on GF’s 22FDX process node. They will develop an SoC integrating ETHZ’s open-source RISC-V cores and eFPGA technology, enabling users to offload critical functions from the processor(s) and implement them in eFPGA fabric. This approach creates multiple hardware co-processors that increase system efficiency and performance while decreasing power consumption.
“The main goal of the PULP program is to use a multi-disciplinary approach to achieve extremely high-power efficiency for computing applications,” said QuickLogic CTO Dr. Timothy Saxe. “QuickLogic has a tremendous depth of experience in achieving low power consumption across a broad range of applications, including AI and IoT at the edge and security, and we look forward to contributing what we’ve learned along with our eFPGA technology to this groundbreaking initiative in low power computing.”
ETH’s PULP platform with the fully integrated eFPGA is expected to be available Q1′ 2019.
QuickLogic is part of GF’s fast-growing FDXcelerator™ partner ecosystem, offering customers ultra-low power (eFPGA) Intellectual Property, complete software tools and a compiler.
The presentations from the SOI Consortium sponsored workshop held during Semicon West are now posted and freely available on the website – click here to see the full agenda with links to the presentations. The workshop, entitled 4G/5G Connectivity: Opportunities for the SOI Supply Chain, was well-attended and generated excellent discussions.
If you don’t have time to look at all of the ppts, here are quick overviews.
Handel Jones is an industry veteran, China expert and longtime follower of the SOI ecosystem. High performance with low power consumption are the key requirements for the continued growth in the semiconductor industry, he said, making FD-SOI the right choice for a wide range of products. Here’s how he sees it:
He estimates the yearly TAM (total available market) for FD-SOI based products in the range of $46 billion over the next 10 years, largely driven by needs for ultra-low power and RF integration. He goes on to break out volumes by applications (including ISPs – image signal processors; and CIS – CMOS image sensors), foundry markets by feature dimension and to map out technology trends.
Mobile Radio Transformation in the Age of 5G: A Perspective on Opportunities for SOI, Peter Rabbeni, Vice President, Globalfoundries.
Peter Rabbeni is an RF expert par excellence, having overseen the shipping of over 35 billion RF-SOI products to date. In his presentation, he details how 5G NR (New Radio) sub-6GHz frequency band specifications significantly increase frequency range and channel bandwidth, and how new band support and MIMO complexity and die size per handset are driving complexity in RF FEMs. Furthermore, 5G/mmWave phased arrays are driving a paradigm shift in the approaches that can be taken, he explains, so greater integration is needed. Here’s a great slide showing where GF’s two main SOI technologies come into play:
Working in partnership with industry leaders around the world, Leti has been the research powerhouse behind all things SOI since the early 1980s. In fact Reuters ranks them #2 in their most recent list of the World’s Most Innovative Research Institutions. This presentation reviews the key technical benefits of FD-SOI for IoT and IMT (that’s international mobile communications, btw).
This presentation really puts the context around engineered substrates. Here are two excellent and useful slides here that identify which engineered substrates go where in the 5G world, and the engineered substrates that Soitec provides. Check these out:
Ultra-thin Double Layer Metrology with High Lateral Resolution, Bernd Srocka, Vice President, Unity GmbH.
In case you’re not familiar with them, Unity provides a wide range of solutions in metrology and inspection. Both the top silicon layer and BOX layer of wafers for FD-SOI applications have draconian requirements that have required new approaches in metrology to ensure the thickness and homegeneity control of these very thin layers.
Shanghai-based Simgui partners with Soitec, using SmartCut™ technology for the production of RF-SOI wafers. It is doubling its capacity to reach 400K over the next year, and expanding into 300mm. China is aggressively working on 5G and plans to deploy 5G commercialization in 2020. Jeff Wang’s is a terrific presentation detailing the rollout. (BTW, in addition to the massive funding effort underway, the government created the National Silicon Industry Group (NSIG) to support the semiconductor material ecosystem in China. You’ll want to keep up with what’s going on here). Here’s the slide that summarizes the SOI ecosystem in China – the presentation then goes on to detail who does what.
Inspection and Metrology Relevance in SOI Manufacturing, Jijen Vazhaeparambil, Vice President & General Manager, KLA-Tencor.
K-T has played a strategic role in the SOI story going back for decades (and in fact they wrote a piece for the third edition of ASN back in 2005!), ensuring metrology innovations for things that hadn’t previously need detection and measurement. With each new set of requirements, they rose to the occasion with wafer metrology solutions that helped increase quality and decrease costs. This presentation recaps some of them.
pSemi (formerly Peregrine, now a Murata company) has staked its claim for having the world’s first monolithic SOI Wi-Fi front-end module (FEM)—the PE561221. This 2.4 GHz Wi-Fi FEM is the first to integrate a low-noise amplifier (LNA), a power amplifier (PA) and two RF switches (SP4T, SP3T) on a single SOI CMOS die. pSemi says it’s ideal for Wi-Fi home gateways, routers and set-top boxes (read the full press release here).
Driving this is the new WiFi standard, IEEE 802.11ax, which launches next year. While it’s largely meant to tackle issues with WiFi in crowded places, it’s also going to be welcome in high-demand home situations. (There’s a good piece on the NetworkWorld site on what 802.11ax will do compared to the current 802.11ac – you can read it here).
With new standards come new challenges. pSemi explains their PE561221 uses a smart bias circuit to deliver a high linearity signal and excellent long-packet error vector magnitude (EVM) performance.
“Traditional process technologies struggle to keep up with both performance and integration requirements, and only SOI can offer the ideal combination of integration and high performance,” says Colin Hunt, vice president of worldwide sales at pSemi.
The monolithic die uses a compact 16-pin, 2 x 2 mm LGA package ideal for either stand-alone use or in 4 x 4 MIMO and 8 x 8 MIMO modules. It is based on pSemi’s UltraCMOS® technology platform—a patented, advanced form of SOI that offers superior performance compared to other mixed-signal processes. UltraCMOS technology also enables intelligent integration, notes pSemi—the unique design ability to integrate RF, digital and analog components on a single die.
Volume-production parts and samples of the PE561221 are now available from pSemi. And this is just the beginning: while the PE561221 is the first product in the pSemi Wi-Fi FEM portfolio, the product roadmap includes 5 GHz Wi-Fi FEM solutions.
The folks at pSemi have been doing RF-SOI for 30 years now, and recently shipped their 4 billionth chip. For the last five years, they’ve partnered with GlobalFoundries.
FD-SOI was a very important topic during the recent Mount Qingcheng China IC Ecosystem Forum. To situate things, Mount Qingcheng, with its lush hills and waterways, is located just outside of Chengdu. That of course is where GlobalFoundries is building its new fab, which will be the first in China to run FD-SOI. Chengdu is also a key city in China’s automotive electronics landscape.
The theme of the forum was Building a Smart Automotive Electronics Industry Chain. Over 260 decision-makers from government, academia and industry attended – and the SOI Consortium had a significant presence. The event was chaired by Wayne Dai, CEO/Founder of consortium member VeriSilicon, and tireless champion of the the FD-SOI ecosystem in China and worldwide. Morning keynotes were given by: Carlos Mazure, Soitec CTO and SOI Consortium Executive Co-Director; Mark Granger, GF’s VP of Automotive Product Line Management; and Tony King-Smith, Executive Advisor at AImotive, a GF 22FDX customer.
BTW, transcripts of all the talks are available through Gasgoo, China’s largest automotive B2B marketplace. You can click here to access them. (They’re in Chinese – but you can open them in the language of your choice using the major translation websites.)
Fan Yi, Deputy Mayor of Chengdu, spoke extensively of FD-SOI in his keynote on the importance of rapidly developing smart cars.
He heralded the “spectacular” new GlobalFoundries fab there. Following a meeting with the company’s top brass the day before, he affirmed GF’s confidence in their investment. There is a solid roadmap for FD-SOI, he noted, and efforts are underway to accelerate the move into production and expand education and training. He cited the benefits of FD-SOI for the entire supply chain, from design through package and test, raising the level of the entire IC industry to new heights. The government, he said, attaches great importance to this enterprise. Their thinking regarding intelligent transport in China is integrated with the overall approach to smart cities.
In his opening remarks, Wayne Dai emphasized the need for China to seize the advantage in the next round of development opportunities in the automotive electronics industry. This year’s Qingcheng forum, he noted, brought together key representatives from across the supply chain, from of the highest to the deepest reaches of the smart car electronics industry, and across markets, technologies, solutions, industrial ecosystem, standards and regulations.
In his talk on how FD-SOI is boosting the accelerated development of automotive electronics, Carlos Mazure presented the SOI Industry Consortium. He noted that the Consortium promotes mutual understanding and development across the ecosystem. SOI is already present throughout automotive applications, he noted. There are currently about 100mm2 of SOI per car, in such diverse areas power systems, transmissions, entertainment, in-vehicle networking and more. SOI will experience especially high growth in electrification, information/entertainment, networking, 5G, AI/edge computing and ADAS. He then went on to give some history and an extensive overview of the major trends and highlights we’ve seen over recent years. He finished by giving examples of convergence across the supply chain with IC manufacturers working with automakers to lower power, increase processor performance and advance 5G.
GF’s Mark Granger addressed the rapid development of automotive electronics. In certain areas, he said, he sees growth rates of over 20%. They are working on building the Chengdu ecosystem, especially for design, and in cooperation with the rest of the supply chain. Furthermore, he reminded the audience, when you talk about cars, travel implies that you also talk about IoT as well as things like infotainment and integrated radar ICs. In addition to cost and power efficiencies, the AEC-Q100 standard for IC reliability in automotive applications is also pushing designers to turn to FD-SOI. In the GF meeting with Chengdu government officials (referenced above in deputy mayor Fan Yi’s talk), he too confirmed their support of FD-SOI as a key technology for China. GF is currently cooperating with about 75 automotive partners, he said, and the company is looking to increase cooperation with partners in the Chengdu region.
Tony King-Smith talked about the 22FDX test chip AImotive is doing with Verisilicon and GF. In case you missed it, in June 2017 AImotive announced its AI-optimized hardware IP was available to global chip manufacturers for license. AiWare is built from the ground up for running neural networks, and the company says it is up to 20 times more power efficient than other leading AI acceleration hardware solutions on the market. In the same announcement, they revealed that VeriSilicon would be the first to integrate aiWare into a chip design,and that aiWare-based test chips would be fabricated on GF’s 22FDX. The chip is expected to debut this year.
While the afternoon agenda was not specific to FD-SOI, it did focus on the “smart cockpit” and “intelligent driving”, with talks by nine leading players in China’s automotive IC and investment communities.
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Note: Many thanks to the folks at VeriSilicon, who wrote up this event for their WeChat feed, and shared photos with us here at ASN.
Manuel Sellier, Product Marketing Manager at Soitec for the FD-SOI (and some other) SOI product lines has written an absolutely terrific primer entitled FD-SOI: A technology setting new standards for IoT, automotive and mobile connectivity applications. It’s in the August edition of the GSA Forum (the GSA is the Global Semiconductor Alliance).
If you know anyone who needs to quickly glean an understanding of FD-SOI that is both in-depth and broad, you’ll want to share this piece with them right away.
Before joining Soitec, Sellier was a chip designer at ST, where he gained deep experience designing FD-SOI chips. What’s more, he holds a Ph.D. in the modeling and circuit simulation of advanced MOS transistors, including FD-SOI and FinFETs. So, he really knows his stuff. But don’t worry that this might be too technical: Sellier’s writing is thoroughly accessible (and engaging!) for anyone in the industry.
He starts with the wafer history, then quickly moves on to the features from the designer’s standpoint. And he puts it all in a business perspective. I can’t recommend this piece enough – even if you think you know everything already yourself, you’re sure to learn something new.
GlobalFoundries has announced that the company’s 22nm FD-SOI (22FDX®) technology has delivered more than two billion dollars of client design win revenue. With more than 50 client designs, 22FDX is being used in power-optimized chips across a broad range of high-growth applications such as automotive, 5G connectivity and IoT.
Their clients chose it for the significant reductions in power and die size relative to a traditional bulk CMOS process, says the company. 22FDX offers the industry’s lowest operating voltage, delivering up to 500MHz frequencies at only 0.4 volts. The technology also delivers efficient single-chip integration of RF, transceiver, baseband, processor, and power management components, “…providing an unparalleled combination of high performance RF and mmWave functionality with low-power, high density logic for devices that require long-lasting battery life, increased processing capability, and connectivity.”
22FDX is in early production, with yields and performance matching client expectations. A recent VLSI Research survey indicated that FD-SOI technology is seen as a complementary technology to FinFET. It’s gaining traction in application spaces such as IoT, where power consumption is important and the product life is relatively short.
“We’re only just beginning,” said GF CEO Tom Caulfied. “We have found a way to separate ourselves from the pack by emphasizing our differentiated FD-SOI roadmap and client-focused offerings that are poised to enable connected intelligence. We will continue to build on our momentum and look for ways to expand our reach to address the evolving needs of the industry.”
Here’s a sampling of customer quotes from the press release (read more here):
GF adds that it is preparing to deliver 12FDX™ technology, which will provide a full node scaling benefit and improved power efficiency for a new generation of applications, from edge-node artificial intelligence and AR/VR to 5G networking and ADAS.
That FD-SOI can be a key to achieving near-threshold voltage design was an important point made during a #55 DAC expert panel. Entitled How Close to Threshold-Voltage Design Can We Go Without Getting our Fingers Burnt? the session was organized by Jan Willis of Calibre Consulting. Turnout was excellent. Btw, Jan (herself an EDA expert) was one of the original advisors in the formation of the SOI Consortium, and while this DAC panel was not meant to be about FD-SOI, it turned out be a focal point.
Near-threshold voltage design* is an especially hot topic for IoT and edge-computing designers, for whom balancing performance, reliability and extremely low power is generally challenge #1. For them, the ability to get chips working at very low voltages translates into battery life savings.
The original goal of the panel was “…to explore how far below nominal voltage we can design, in what applications it makes sense and in what ways it will cost us.” The description in the #55 DAC program noted that “Energy consumption is the driving design parameter for many systems that must meet ‘always-on’ market requirements and in IoT in general. For decades, the semiconductor industry has attempted to leverage the essential principle that lowering voltage is the quickest, biggest way to reduce energy for a SoC. Some today contend sub-threshold voltage design is viable while others argue for near-threshold voltage design as the minimum.”
(Update 2 August 2018: a complete video of this panel is now available on YouTube — click here to view it.)
The panelists included:
Brian Fuller of Arm served as moderator.
Following the panel Jan published the following excellent recap on LinkedIn. She graciously agreed for it to be reprinted here in ASN, for which we thank her. So without further ado, read on!
First published on LinkedIn, June 27, 2018 by Jan Willis, Strategic Partnerships & Marketing Executive
Brian Fuller, Arm, skillfully guided a group of experts through the challenges of near-threshold design to conclude that the adoption is going to start gathering pace in a panel session at the 55th DAC in San Francisco on Monday, June 25.
Scott Hanson, CTO of Ambiq Micro, led off by saying the list of what’s not challenging is a much shorter list but that by taking an adaptive approach, they have been successful. It’s required innovating throughout the design process including test where Scott said they had create their own “secret sauce” to make it work. Later on in the panel, Scott described designers in near-threshold as “picojoule fanatics” to overcome the limitations in design tools which are geared towards achieving performance goals.
Lauri Koskinen, CTO of Minima Processor, agreed that adaptivity is key. Minima says it has to be done in situ in the design to make it robust for manufacturing while useful across more than one design. Later in the panel, Lauri indicated that FD-SOI is like having another knob available for optimizing energy in the Minima approach to near-threshold design.
Mahbub Rashed, head of Design and Technology Co-Optimization at GlobalFoundries, highlighted the need for more collaboration between EDA, IP, and foundries to support near-threshold design but noted a lot of progress has been made on FD-SOI processes. Mahbub cited models down to 0.4V for FD-SOI processes are available now and GlobalFoundries is able to guarantee yield.
Paul Wells, CEO of sureCore, validated that sureCore has bench marked their memories on GlobalFoundries FD-SOI with success. He reflected that FD-SOI has rapidly established itself as cost effective for a number of emerging markets. The panel all agreed that achieving quality on the memory at near-threshold voltage was much tougher than for digital IP. [Editor’s note: sureCore‘s CTO wrote an excellent summary of their SRAM IP for FD-SOI in ASN back in 2016 – you can still read it here.]
Paul went on to summarize at the end of the panel that near-threshold voltage is the way of the future and that it’s gathering pace. Mahbub called upon the EDA community to step up to improve the tools for low energy design. Lauri and Scott both summarized that there were drivers emerging that will grow the addressable market for near-threshold voltage design. Lauri pointed to growth coming from the applications that require edge computing which he thinks will require near-threshold voltage design. Scott concluded the panel by pointing out that there’s been a tremendous increase in performance of near-threshold voltage designs which will increase the addressable available market in the future.
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This piece was first published by Jan Willis on LinkedIn, June 27, 2018. Here is the original.
* As explained by Rich Collins of Synopsys in the TechDesign Forum: “Operating at near-threshold or sub-threshold voltages reduces static and dynamic power consumption, at the cost of design complexity. […] A transistor’s threshold voltage (Vth) is the voltage at which the transistor turns on. Most transistor circuits use a supply voltage substantially greater than the threshold voltage, so that the point at which the transistors turn on is not affected by supply variations or noise. […] In sub-threshold operation, the supply voltage is well below the Vth of the transistors. In this region, the transistors are partially On, but are never fully turned. Near-threshold operation happens between the sub-threshold region and the transistor threshold voltage Vth, or around 400 – 700mV for today’s processes.