The great divide between consumer and industrial flash memory
November 07, 2016
Data storage, including flash memory, is all the same, right? Well, not exactly. And the divide becomes far wider when you're talking about industrial...
Data storage, including flash memory, is all the same, right? Well, not exactly. And the divide becomes far wider when you’re talking about industrial applications that may be operating in harsh environments and need to tolerate heat, cold, shock, and vibration. A second consideration is the frequency in which a user can or will visit the system’s location. If deployed in a remote location, the frequency is likely to be very low.
Ultra-rugged solid-state drives (SSDs) that are based on NAND flash memory and can withstand harsh conditions in thermal, mechanical, and electrical backdrops are the clear choice here. Known as “industrial grade flash drives,” they offer superior memory, physical construction, and controller architecture and firmware design. With no moving parts, they’re obviously faster, smaller, and easier to use.
The drives’ durability comes from detection mechanisms like error correction code (ECC) and robust flash management techniques such as wear-leveling, bad block remapping and write abort handling. Wear-leveling provides write endurance by distributing writes evenly across the device.
The three key building blocks in a rugged flash design are the flash memory cells, the controller architecture, and a rugged construction. With respect to the cells, as node geometry (also known as trace width) of flash chips gets smaller, error rates become a significant challenge due to the closer proximity of neighboring cells in the NAND silicon.
The smaller trace widths let the memory chips reduce the cost per gigabyte while also lowering power consumption. Unfortunately, smaller geometries have a profound effect on the NAND memory cells endurance because of the higher error rates and inter-cell noise coupling.
But the trouble doesn’t end there, as all NAND flash memory chips are bound to have errors due to things like charge leakage, sense amp errors, disturbance due to noise coupling, device wear out, and so on. The solution is to incorporate ECC hardware to correct these errors on the fly.
Finally, it’s imperative to look at how the device is physically constructed. The casing, preferably constructed with a die-cast metal chassis, must be rugged enough for protection against extreme environments. It must be rated for the industrial temperature range and have been temperature-screened. And the PCB should comply with superior signal integrity requirements.
Cactus Technologies designed its Industrial Grade products with an optional -45°C to +90°C operating temperature and also developed a production screening process that enables it to offer an extended temperature range of -40°C to +85°C on select MLC NAND products. For example, its 240S Series Commercial Grade 2.5”, SATA III SSD, mSATA, and 240 Series Commercial Grade SD Card have an optional extended temperature range.
The industrial-grade products from Cactus Technologies include industrial CompactFlash, SD Cards, microSD cards, PC Cards, mSATA flash, CFast, and USB flash drives. These products are based on SLC NAND flash cells and offer extreme reliability, long lifecycle, and the locked-BOM feature.
Note that Cactus Technologies has authored a whitepaper dubbed Rugged flash memory: Anatomy of an industrial storage device that goes into much more detail on this topic.