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Depending on who you talk to, the removable memory card, most familiar in the form of a Secure Digital (SD) or CompactFlash (CF) form factor, is waning in favor. Rather, embedded options or even solid-state drives (SSDs) with small form factors have become the memory solution of choice because of their ability to handle the increase in data usage for some applications.
While it’s true that many consumer devices now have sufficient onboard storage capacity thanks to the Universal Flash Storage (UFS) specification as well as the multichip package (uMCP) that combines flash storage and DRAM, emerging use cases in the industrial and automotive market are demonstrating that having an easily removable form factor is quite useful, if only to help increase capacity without having to dismantle the entire system.
The ability to swap out a memory device easily is certainly a time and cost saver for automotive applications when it fails, especially when the memory is causing an otherwise functional system to fail. A good example is the flash wear out that prompted a Tesla recall, wherein a failing eMMC NAND flash memory device linked to a touch screen can lead to the entire “media control unit” being bricked, cutting off access to the federally mandated backup camera as well as any functionalities routed through the touchscreen, such as HVAC controls and even turn signals.
A removable memory device makes it easier to swap out the affected device. The SD card form factor is one Micron Technology is bullish about for automotive applications, as well as complex memory and storage demands at the intelligent edge.
At Embedded World 2022, Micron announced it was sampling its i400 microSD card with a density of 1.5 terabytes (TB). Designed specifically for industrial-grade video security applications, the new card uses the company’s 176-layer 3D NAND and proprietary features purpose-built for industrial applications.
Micron’s i400 microSD can concurrently handle 4K video recording and up to eight AI events per second, such as object detection and classification, including license plate or facial recognition. It can also handle five years of high-quality continuous 24×7 recording.
Video is driving removable card capacities, performance
Dave Henderson, director of the industrial segment at Micron, said the i400 micro SD is the first to market at that density level, and targeted to drive adoption for use cases in the industrial segments where video is strongly used. It benefits from the company’s development around retention as well as optimization around the sequential read and sequential write optimization.
“As the world moves forward in its AI and algorithmic approach to what’s done in and on the camera, both of those things are important, both for recording, 24/7 recording of sequential data, but then also the capturing of what’s effectively metadata used for some of the AI triggers and activities,” Henderson said.
Although the consumer portion of the SD card market remains the largest, the industrial side as well as growth of drones are rife with opportunities for an SD card slot, Henderson added. Just about any scenario where there’s a camera capturing video, such as security, law enforcement, and fleet management, is an opportunity for removable flash memory cards.
“As the performance of these devices gets better, they’re implementing some more real time feedback and analytic activities that are happening inside of it,” Henderson said. Those analytics now include advanced AI activities that are performing detection, classification, alerts, and contextual analytics, he added. “It’s definitely a growing activity and where videos involved is kind of where we see the opportunity for the cards.”
The video capabilities for the new i400 microSD card loop back to the automotive market, added Robert Bielby, senior director of Automotive Systems Architecture and Segment Marketing at Micron. Tesla has set the standard when it comes to having cameras all around the car, and other OEMs are picking up the idea of a car having digital video recording capabilities that chronicles every mile of travel for a variety of reasons, including insurance purposes in case of a collision.
“People want to be able to hand over the recording to their insurance company so that they can replay it and see exactly what happened.” Although there may be the argument that this will go up into the cloud eventually, an SD card is a handy form factor, Bielby noted. It’s inevitable that more and more applications will be downloaded into the vehicle without a good understanding of memory and storage endurance requirements.
Industrial, automotive environments require ruggedness, reliability
Automotive applications require reliability and ruggedness. As a result, the market has drawn inspiration from the industrial segment, which also makes use of cameras, Henderson said. “There’s some pretty good value propositions there.”
Even though some data is transferred to the cloud, “what they’re finding is that all of that data isn’t necessarily the top-quality data and doesn’t deserve to be transferred to the cloud.” He said the removable cards available today can retain four months worth of footage, which can be quickly pulled on demand.
Swissbit, an industrial storage and security products manufacturer, also sees the industrial space as a prime market. But while Micron is talking about SD cards, Swissbit sees CFexpress as the next most important leap forward in the development of industrial memory cards because of its performance, temperature resistance, robustness, and flexibility.
CF has long been associated with digital cameras, and today CFexpress is the ideal choice for all applications that require a quick replacement or memory upgrade despite the technology being perceived by some as a “sunset” business more than a decade ago, said Grady Lambert, general manager for North America at Swissbit. “The sun still hasn’t set on these removable cards.”
And it’s the removability that’s appealing for many markets, whether it’s industrial, medical, or gaming, he added. Factory automation can take place in a dirty environment where a device may need to be easily swapped out without putting a significant pause on operations. The flexibility, robustness, and performance of CFexpress cards, such as the G-20 series from Swissbit, makes it especially suitable for industrial use cases, Lambert explained, and it can be further optimized with special firmware adjustments.
But just as Micron sees SD cards meeting automotive application demands, there could be opportunities for CFexpress even with its capacity limitations. This is because PCIe and even NVMe is starting to gain traction in the vehicle and many systems are partitioned from each other. “CFexpress enables the host to communicate directly to the card with a refined and tailored instruction set,” Lambert said.
It’s not just cars that can make use of removable cards, but the broader transportation segment. For example, trains where a removable, ruggedized device can be easily pulled from the equipment for black box type applications and other data logging functions.
Swissbit also offers SD cards for transportation, industrial, and factory automation as well as security applications, with drones being a growing segment of the latter, Lambert said. Government and military use cases necessitate captured data can’t be manipulated, so the security features in an SD card allows the information to be safely removed and taken to where it can be analyzed.
Lambert said Swissbit often encounters customers who’ve initially gone with embedded eMMC for a design and then backed away from that decision because if there’s ever an issue with the flash storage device, the only way for their end customer to resolve the problem is to return the entire system. “We want to give our customers options, especially in the industrial segment.”
Even as the security and surveillance market transitions to cloud-based solutions, there’s still a significant portion of that market that requires a card to be removable.
Removability is key to flexibility, expandability
The ability to change out flash memory that’s typically been soldered into connected devices and embedded applications was the motivation behind the JEDEC’s Crossover Flash Memory (XFM) Embedded and Removable Memory Device (XFMD) standard. Finalized in August 2021, the spec outlines a universal data storage media providing an interface between NVM Express (NVMe) and PCI Express (PCIe) in a small, thin form factor.
Measuring 14-mm by 18-mm and 1.4 mm high, the XFMD form factor is smaller than a standard SD card but larger than a microSD card. It is also designed to be a replaceable storage medium for devices that are typically soldered and meant to stay put for the lifespan of a device. Targeted use cases include PCs, gaming consoles, virtual and augment reality gear, video recording devices such as drones and surveillance systems, and automotive applications where components are typically qualified to last a decade.
That being said, JEDEC’s approach to developing a standard wasn’t to aim for any specific market, said Bruno Trematore, co-chair of JEDEC’s UFS task group. “What we have is more a technical discussion. Nevertheless, from the technical specifications, you can have an idea of what kind of audience you are targeting.”
On one side, he said, there’s UFS cards that target low-power applications, such as a smartphone, while the XFM specification’s removability allows for replaceability. The removability factor makes it appealing for a variety of scenarios when memory needs to be replaced because it’s worn or there’s a design to expand system capacity. “UFS card and XFM card or device are quite different standards.”
No matter the specification, innovation with removable memory and storage cards include advancing performance while reducing power consumption, but backwards compatibility is critical as you add features, Trematore said. “You don’t want to change your software stack.”
On the other hand, he noted, there may be a desire to simplify without throwing out everything that’s already been done – it’s a fine line.
JEDEC standards are open and driven by members, added Hung Vuong, chair of JEDEC’s JC-64.1 subcommittee. “They will bring the features and requirements in, and we’ll try to work with members to standardize it.”
A major challenge from a JEDEC perspective for future standards is addressing the thermal effect, even as it continues to double the performance and optimize power. “We’re still going to hit a thermal limit sooner or later and having small form factors is not going to help that.”
One trend that’s becoming increasingly popular for many systems designs is not having a memory that’s soldered onto the PCB, said Trematore, and the flexibility of being able to replace a memory card is how a standard can help achieve some cost reduction. “Everybody’s really looking at the very last dollar in their bill of materials, so some of these standards may be really cost effective.”
— Gary Hilson is a general contributing editor with a focus on memory and flash technologies for EE Times.