The birth of automotive storage can be traced back the mid-90’s and the adoption of built-in car navigation systems in high-end cars. Since 1996, automotive specific hard disk-drives (HDDs) have steadily increased in capacity, with the largest automotive HDDs reaching capacities of 320Gbyte.
Over the past 20 years, storage devices have evolved from being a feature of high-end cars to being present in nearly all new cars.
The average memory capacity installed in a car is estimated to expand from 15Gbyte to 35Gbyte in 2018 to greater than 60Gbyte in 2025. And much of this growth will be met by solid state drives using NAND flash memories. The worldwide market for automotive NAND is expected to double and reach a value of more than $600m by 2018.
Mapping and media data account for 70 to 80% of all storage capacity in cars. Here navigation with 3D graphics, extensive point of interest data and satellite images similar to those displayed by Google Earth are further increasing the hunger for storage capacity.
With the inevitable move to more advanced driver assistance systems there will be a requirement for even more memory intensive multi-layer high definition maps.
Other applications driving the demand for automotive storage are voice recognition and speech synthesis which need to support several languages. Many cars already include natural-language speech recognition.
In addition, the constant increase of application software is requiring more memory space. Users expect the same functionality as they are used from their smartphones. Modern high-end head-units integrate software and applications from dozens of different suppliers.
Another factor impacting upon the demand for storage capacity is the connection to the internet. It is expected that in the next two years 60% of all new cars will have a wireless connection of some sort.
Through the use of mobile internet connections, cloud storage will perhaps become used for memory-hungry applications. But drivers and passengers will expect most applications to function without a stable internet connection.
For example new tiles of HD-maps could be downloaded depending on the planned trip. Or in addition to standard voice recognition, natural speech recognition could be offered through online services. This will give every car manufacturer the ability to define what it considers to be the sweet spot between service availability and the requirement for total storage space.
Much of this growth will be in the entry-level and mid-range car segment where infotainment and navigation systems tend to include between 4 and 32Gbyte of storage, and at these capacities NAND flash-based storage is particularly cost effective.
Toshiba’s family of NAND flash memories with control functionality such as error correction codes (ECC), wear levelling and bad-block management, is called e-MMC.
High-end navigation systems today often use dedicated automotive HDDs with up to 320Gbyte capacity for map and media data plus 16 to 32Gbyte solid-state drives (SSDs) for application data.
Some car manufacturers have already replaced the HDDs by SSDs with 60 to 200Gbyte NAND in designs that are entering production. Others have moved directly from HDDs to solid-state drives of 64 to 128Gbyte .
While Toshiba plans to support its customers with automotive HDDs for at least the next seven to eight years, it is expected that all projects that are scheduled to enter production from 2020 onwards will be based on one form or other of solid-state storage.
The reason for the shift from traditional HDDs towards SSDs using NAND flash memory can be explained by the greater resistance to environmental conditions exhibited by NAND flash memory devices that do not have any moving parts.
Another growing market for NAND memory in the automotive sector is the instrument cluster market. With the strong reduction of prices for colour TFT displays, hybrid clusters are becoming the default for mainstream cars.
In the premium segment there is a strong move towards fully digital clusters. Both require more memory space for advanced graphics than can be accommodated by embedded or external NOR flash.
Memory devices installed in cars need to accommodate a wide range of environmental conditions, such as temperature, humidity and also need to withstand constant vibrations and shocks. Here solid-state memory provides a clear advantage over mechanical HDDs.
Cars have a typical product lifetime of 15 years and owners expect their systems to function and their media to be not corrupted even after leaving the car parked in the dessert for weeks. Such scenarios are certainly demanding for NAND flash, where only a few electrons are stored per bit, and charge leakage over time may lead to errors.
In addition to the security of error correction codes, the controller needs to manage the NAND flash to ensure data integrity. A close co-operation between car manufacturer, the tier-one designing the system and the NAND flash supplier has proved to be helpful in reaching optimal designs.
Another challenge is the long development and qualification cycles as well as typical product life cycles compared to mobile or consumer applications. NAND flash technologies typically evolve to the next process step every 12 months. And cost pressures drive the system makers to apply the latest available technology for new designs.
But to avoid expensive changes and re-qualifications during production this same technology needs to be available in the long term. Again, a close partnership between supplier and customer will help to find the best possible trade-off.
Toshiba currently supplies automotive products based on 19nm NAND flash. Over the past two years products with a total density of more than 100 million gigabyte were shipped and car manufacturers and OEMs have gained good experience with integrating these into the car.
While, 15nm NAND is currently undergoing AEC Q100 qualification and a number of manufacturers are starting to specify these increased bit density memory devices.
In the slightly longer term, 3D NAND will also become of interest as the higher bit densities will help keep pace with increased demand for higher capacities. In addition, the charge trap cells have greater write/erase cycle resistance.
A three-dimensional (3D) stacked cell structure flash memory can surpass the capacity of mainstream two-dimensional NAND flash memory while enhancing write/erase reliability endurance and boosting write speeds.
Another critical requirement in automotive applications are read and write performance that enable shorter boot times. Here the move to the UFS interface will bring advantages with an increased maximum bandwidth of 11.6Gbit/s. Sequential read speeds can reach 600Mbyte/s and write speeds 180Mbyte/s – tripling the performance of e-MMC devices using a memory card interface compliant with JEDEC/MMCA Version 4.5/5.0/5.1.
At the same time UFS offers increased random read and write performance and also very low stand-by power consumption, below the alternative PCIe / NVMe interface. It also offers a wide feature set supporting reliability, security and boot performance.
Volker Schumann is senior manager, automotive sales, Toshiba Electronics Europe