The memory and data-storage capacities of automotive systems are rising rapidly, driven by myriad infotainment systems as the industry makes progress on the road to full autonomy. Energy consumption alone is enough reason to streamline and consolidate where possible, but careful thought must be given to make sure mission-critical operations are prioritized.
Memory and storage consolidation also extends to the many electronic control units (ECUs) that are spread across vehicles as automotive systems look for inspiration from other computing architectures, including smartphones, the Internet of Things (IoT), and data centers; they all can inspire how existing technologies can be more integrated to meet automotive application requirements while addressing energy-consumption concerns and delivering high reliability.
There’s a delicate balance between segmented automotive systems necessary for protecting driving systems from any interference and an increasing need for an architecture that ties computing and memory together to support a “digital cockpit” for the driver.
Data-Driven Dashboards Demand More Storage, Memory
Automotive dashboards have come a long way from cassette players being the most exciting add-on — and we’re well beyond Bluetooth and USB connectivity being a novelty. Infotainment systems are rapidly evolving to deliver a more immersive experience for both drivers and passengers, which is driving up the amount of electronics content — including memory and storage.
A key part of today’s automotive infotainment systems is the advanced driver assistance system (ADAS), with a rear-view camera becoming standard on all vehicles. Even without much autonomy there’s a lot of computing going on in the vehicle to help with navigation and safety, as well as entertainment.
Today’s infotainment systems can be found throughout the vehicle and fall under four categories:
- Digital Instrument Cluster: In addition to the usual dashboard instrumentation such as a speedometer, today’s instrument clusters are fully digital and adopt high-resolution screens that are increasingly customizable by the driver and include vehicle telemetry and maps on secondary screens.
- Head Unit: This is where all the modern-day features of today’s vehicle can be found when front-seat passengers enter the car — rather than a cassette player, the radio will be complemented by connected car applications such Apple CarPlay and Android Auto, built-in GPS, and satellite radio services such as Sirius XM. All these features are expected to be immediately available when the key is turned.
- Heads-Up Display (HUD): A relatively new feature in vehicles, a HUD projects information only to the driver on transparent glass located above the steering wheel. Like the traditional instrument cluster, information on the HUD includes speed, telemetry, and maps.
- Rear-Seat Entertainment (RSE) Unit: Gone are the days of a backseat passenger needing to bring their own entertainment to pass the time on long trips. Instead of a Walkman or book, rear-seat passengers have integrated entertainment options that include dedicated media player mirroring options from Android Auto and Apple CarPlay.
All this rich infotainment media in the front of the car alone requires a great deal of computing performance, including memory and data storage, and a unified digital cockpit benefits from an architecture that’s also consolidated.
Automotive Has Many Memory and Storage Options
All these digital systems are informed by data collected throughout the vehicle — right down to the power locks and windows so that the driver knows what’s open and what’s closed.
It used to be that every function had its own ECU, but those are also consolidating, so that rather than having a fixed-function ECU, the ECU is now software-defined. Meanwhile, even partial autonomy adds more data and functions that must be supported by ECUs, memory, and storage, including ADAS features such as adaptive cruise control, lane keeping, and automatic breaking — all of which are informed by sensor data from cameras, radar, and LiDAR. All the connectivity that informs digital cockpits, be it Wi-Fi or 5G, also makes it easy to upgrade the car with new software and patches, which is in turn driving memory and storage requirements.
The memory and storage devices used in the automotive industry today are there because they are well-understood and reliable — safety is key in automotive, as is longevity. These devices are expected to last as long as the life of the vehicle without needing to be replaced. They differ widely in capacity and performance depending on the application:
- NOR Flash: Because it’s a non-volatile memory, NOR flash is ideal for storing application code and for execute-in-place (XIP) tasks that bypass an external DRAM by enabling a host processor to run code directly from the NOR flash device. These devices also boot up quickly, which makes them perfect for the instrument cluster and ADAS because rear-view camera display is available as soon as the key is turned.
- Ferroelectric RAM (FRAM): Still often described as an “emerging” memory, FRAM is also non-volatile and has potential to replace NOR flash for some applications. It’s best-suited for data logging in most sub-systems, such as dashboard instrumentation, battery management, stability control, power train, engine controls, and smart airbags.
- Magnetoresistive Random-Access Memory (MRAM): Another emerging memory, MRAM is suitable for the automotive industry due to its non-volatility and high reliability at high temperatures. It’s also fast, making it a good choice for sensors where data is monitored and written in real time.
- Low-Power DRAM (LPDDR): Already a preferred memory for smartphones because it combines performance with low power consumption, LPDDR meets the automotive requirement for reliable ADAS technologies that might use functional safety-evaluated DRAM, including automatic emergency braking systems, lane-departure warning, adaptive cruise control, and blind-spot-detection systems. DRAM maker Micron Technology has its LPDDR5 hardware evaluated to meet the most stringent Automotive Safety Integrity Level (ASIL), ASIL D, a risk classification scheme defined by ISO 26262.
All these memories are complemented by various storage types — essentially various flavors of non-volatile NAND flash.
At the lower end, there are some uses for removable flash storage formats — CompactFlash and Secure Digital cards are a flexible option for digital maps and dash cameras. The Embedded MultiMediaCard (eMMC) interface standard, although no longer being updated, remains widely used in automotive applications such as telematics, infotainment, and ADAS because it’s a proven technology that delivers the longevity automakers want. It has been supplanted by Universal Flash Storage (UFS), an actively updated interface, although in the embedded space; eMMC can best address the lower-capacity applications with a lower power profile.
Both eMMC and UFS are well-suited for ADAS, in-vehicle infotainment (IVI), telematics, and autonomous drive systems, but as capacity requirements grow for infotainment and mission-critical applications, an SSD becomes the best option, and even adopting new interfaces such as Non-Volatile Memory Express (NVMe).
Consolidated Systems Must Prioritize Safety and Reliability
Even with all this diversity, there’s a growing need for a more consolidated architecture to reduce complexity even as the cockpit becomes more digitized and more power hungry.
The nature of the automobile means there will always be a certain degree of distribution of systems with multiple memory types and ECUs. However, the higher capacity of SSDs means it makes sense to consolidate storage of data for multiple systems in one place. Increased autonomy and cockpit digitization along with the data growth means moving away from a fragmented architecture with distributed ECUs toward a single domain controller.
This transition toward clustering would see more unified storage that holds both mission-critical data and entertainment content, albeit segmented and prioritized. Common pools of data would be leveraged for efficiency — all maps are stored in a single location but used for different applications, not unlike the architecture of a server, including virtualization. Two different applications can access the same storage, with mission-critical data prioritized for availability and redundancy, bearing in mind there are risks when putting mission-critical ADAS features on the same data-storage media as onboard entertainment for the kids.
Rather than adding more functionality and more capability in a piecemeal manner, designers are shifting toward taking a more holistic view toward the architecture, and that includes a consolidated, centralized storage approach instead of having discreet devices. While emerging memories may have their use cases, proven storage technologies such as eMMC, UFS, and flash SSDs combined with proven memories such as NOR flash, LPDDR, and GDDR will be the preferred candidates for any consolidated automotive system that will have to balance cost and efficiency with safety and reliability.
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