Remember when a state-of-the-art car entertainment system was one that could play multiple CDs? Those days are long gone. Today's automotive infotainment systems are complex embedded subsystems that bring together such diverse functions as MP3 music playback, GPS navigation, voice recognition, hands-free cellular connectivity, DVD video, and even Internet browsing.
As the auto infotainment system expands into a wider range of multimedia applications, its storage subsystem plays an increasingly crucial role. Music and video files must be stored and quickly accessed. Large mapping data files for 3D GPS systems must be rapidly searched and displayed, and audio files for voice recognition must be synthesized and stored.
HDDs are cost effective
Most auto infotainment systems in use today rely on a ruggedized hard disk drive (HDD) for data storage. These devices typically offer 40 to 50 GBytes of capacity. As a well-established, proven technology, HDDs offer a number of attractive advantages. On a dollar-per-GByte basis, they present designers with a cost-effective solution. In applications that can overcome the HDD's inherent seek and rotation latencies, where the majority of read accesses are sequential for example, HDDs can stream large amounts of data in a short period of time.
In today's increasingly complex auto infotainment systems, however, other factors play an ever more important role in the selection of a storage subsystem. In many applications, the large quantities of data storage available on HDDs offers little benefit to auto infotainment system designers. Most systems only require four to eight GBytes of memory to adequately serve today's multimedia applications. Moreover, the automotive industry's high expectations for reliability and demanding requirements for ruggedness place a premium on storage subsystems that can offer high levels of shock, vibration, temperature, and moisture tolerance.
Given these trends a new generation of industrial-grade, small form factor solid-state drives (SSDs) offer designers of auto infotainment systems a highly attractive storage option. These new storage products come in either integrated or discrete versions. Integrated NAND modules, such as the "industrial grade" NANDriveTM line from Silicon Storage Technology (SST), combine an integrated ATA controller with one or more NAND flash die in a single package (see figure below). These devices offer complete IDE (Integrated Drive Electronics) flash disk drive functionality and compatibility in a compact BGA package as small as 12 x 18 x 1.4 mm. The designer simply mounts the BGA on the system motherboard. On boot-up, the system recognizes the NANDrive via the ATA or IDE interface as a system drive.
As an entirely silicon-based storage solution with no mechanical moving parts, small form factor SSDs such as NANDrive offer the designer the ability to meet the automotive industry's stringent shock and vibration specifications. From a performance standpoint, small form factor SSDs not only eliminate the time-consuming seek process a disk-based storage system must perform, which can take on average 13 ms, they also offer sustained write and read performance of up to 30 MBytes/sec. The current generation NANDrive devices from SST are qualified across the industrial temperature range and offer up to 8 GBytes of storage.
What is often overlooked are the major advantages small form factor SSDs offer in terms of footprint and performance. Over the past decade as automotive manufacturers have introduced a growing number of electronic subsystems into their vehicles, reducing the electronics footprint has become an increasing priority. For example, today's average automobile integrates anywhere from 30 to 50 microcontroller-based systems.
While HDD manufacturers have achieved continual advances in their ongoing effort to shrink the footprint of their products, today's drives still require much more space than silicon alternatives. As an example, a standard size 40 GByte HDD measures 70 x 100 x 9.5 mm. The NANDrive occupies 12 x 24 x 1.4 mm, or 1/120th that of the HDD. Weight savings are also impressive. At 0.8 grams, NANDrive weighs less than 1/100th of the HDD.