Embedded SSDs: SanDisk’s iSSD puts 64Gbyte SATA SSD on a BGA device measuring only 16x20mm, 1.85mm high

The convenience of SSDs that look like HDDs is that they can seamlessly plug and bolt into the same mechanical and interface infrastructure as their mechanical brethren. Many, many embedded designs would happily forego the mechanical compatibility in exchange for a smaller volumetric requirement because many embedded systems, like nearly all mobile devices, are quite short on extra volume. That’s precisely the market SanDisk targets with its new iSSD (integrated SSD), which crams an entire SSD with 4- to 64Gbyte capacities and a 3.0Gbbps SATA II interface into a ball-grid array package with a 16x20mm footprint and 1.85mm height.

SanDisk’s iSSD also foregoes the conventional SATA connector (too big) and instead brings out the standard SATA interface to balls on the BGA. No connector and no SATA cable. Just pc board traces to deal with.

Weight is also important in most volumetrically challenged embedded designs and SanDisk’s iSSD weighs in at a mere 0.83g. Compare that to aluminum-encased 1.8-inch SSDs, which weigh approximately 35g, and 2.5-inch SSDs that can weigh 70 to 90g. There’s as much as a 100x difference in weight!

The SanDisk iSSD’s power consumption is likewise small: 60mW in sleep mode, 1W in active mode, 180mW average. Read and write speeds for the iSSD are “up to” 160 and 100 Mbytes/sec respectively. For PC-centric applications, the iSSDs support the SMART feature common to HDDs and SSDs and the TRIM feature that’s becoming increasingly common for SSDs.

Another figure of merit that concerns embedded designers is SSD reliability. Every storage designer is aware of NAND Flash’s wearout mechanisms. Here, SanDisk provides usable reliability ratings as a long-term data endurance (LDE) specification in the form of a spec called TBW (Terabits writted), which specifies how much data can be written to the SSD over its life. SanDisk rates the LDE of its 4- to 64Gbyte iSSDs at 2.5 to 40 TBW, depending on capacity. (The TBW rating increases with overall SSD capacity.)

Like all SSDs, SanDisk’s iSSDs have no moving parts, thus has no mechanical wearout mechanism, and they are pretty rugged with respect to temperature and shock.