Recent NAND Trends (And Why Reliability Is So Crucial)
The year 1987 was an exciting one for tech professionals. It marked the introduction of NAND flash, which made its debut at the IEEE International Electron Devices Meeting in San Francisco. Since that time, innovations in embedded designs and NAND trends have taken off. One of the top items on every developer’s wish list was to increase the storage capacity while keeping the price point on a downward trend. This begs the question: Has reliability been jeopardized in the name of capacity and affordability?
Evolving Data Storage: From SLC to MLC
First, let’s take a look at the remarkable advances in data storage capabilities. The first type of non-volatile flash memory cell developed was the single-level cell (SLC). SLC flash stores one bit per cell. An SLC can have one of two voltage levels: 1 or 0. Later, multi-level cells (MLC) were developed. Each MLC memory cell is capable of storing two bits, and a variety of values is supported: 00, 01, 10, and 11. It’s thanks to the innovative MLC design that data storage capacity has increased so rapidly.
Changing the Data Storage Game: From SLC and MLC to TLC
In the continual quest to squeeze more data into less space, it’s only natural that some developers would shift toward the next incarnation: TLC, or tri-level cell (sometimes referred to as triple-level cell, MLC-3, 3-bit MLC, or X3). As you might expect, TLC can store three bits per cell. This complex cell architecture supports eight different states in order to store and retrieve three bits of data. Compare this to the original SLC architecture, which only supports two states. Tri-level cell technology is gaining ground in a number of applications, like USB drives, mobile phones, and digital cameras, thanks to its high data storage capacity and low price point.
Comparing SLC, MLC, and TLC in Light of Reliability
There’s no question that MLC and TLC both offer valuable contributions across multiple industries, and it’s likely that the NAND architecture will continue to evolve, offering greater capacities in small packages. But MLC and TLC might not necessarily be the most appropriate choice for every data storage need, as the reliability has yet to catch up to the capacity potential. The number of erase cycles per block is a critical indication of a storage device’s reliability. It’s possible for TLC NAND to have just 300 erase cycles per block. MLC NAND typically has about 3,000 erase cycles per block. SLC is the clear winner in this category, with about 50,000 to 70,000 erase cycles per block.
Evaluating Silicon Trace Width
Of course, the number of erase cycles per block isn’t the only factor to consider. The trace width of the silicon is also changing. SLC is still available in geometries of 4x, 3x and 2x nm, but 2D MLC’s trace width has shrunk down to 15 and 16mn in order to increase density. As a result, there is a greater potential for disturb and read disturb errors. This means more memory can fit onto the silicon, but at the cost of reliability. 3D NAND technology is becoming the standard for consumer applications and will soon become more mainstream for embedded applications as well. We will discuss 3D NAND more in a future article.
At Delkin, we pride ourselves on innovative, high-capacity designs that exceed developers’ reliability expectations. Here, you’ll find a number of industrial storage options, including SLC and MLC designs. Connect with a knowledgeable representative at Delkin today, and find out for yourself why we’ve built a stellar reputation for rugged, reliable storage solutions.