NAND flash memory is a type of non-volatile storage technology that does not require power to retain data. An important goal of NAND flash development has been to reduce the cost per bit and to increase maximum chip capacity so that flash memory can compete with magnetic storage devices, such as hard disks.
NAND flash memory is based on technology like non-volatile storage. It does not require continuous power to keep the data secure. The main reason for creating NAND flash memory is to make the bit’s cost and the cost of making chips minimum. This flash memory can be brought up to make the cost equal to the hard disk so that the common customer can easily buy it. We can easily store the largest number of files on a hard disk, but NAND is currently not possible in flash memory as its cost is very much higher in the market. The company currently uses NAND flash memory in the camera, music players, and smartphones.
NAND memory cells are made of two gate types that are control and floating gates. Both gates can assist in managing data flow. A voltage charge is sent to the control gate to program one cell. NAND flash memory vendors include Samsung, Toshiba, Intel, and Western Digital & Micron Technology.
NAND Flash Memory Operations
NAND set the number of writing cycles. NAND degradation is typically incremental; a term is known as wear-out, as individual cells fail, and overall output degrades. Few vendors over-provide their systems by providing more memory than stated to help compensate for that.
The user simply buys a new one when a NAND card wears out, and the system continues to work. Manufacturing companies have dramatically reduced the price of consumer electronic products bypassing the cost of extra capacity to the consumer.NAND flash can accept only a small amount of write cycles per row. It delivers easy-to-read access, but it is not as fast as static ROM or RAM. The system is shock resistant and can withstand high and low temperatures as well as water submersion, so it performs better in handheld devices than hard discs.
Types of NAND Flash Memory
The popular types of NAND flash storage include SLC, MLC, TLC, QLC, and 3D NAND. What’s distinguishing each form is the number of bits used by each cell. The more bits in each cell, the less costly it would cost to store NAND flash.
SLC cells, or single-level cells, store each cell one bit. SLC has maximum endurance but is also the most expensive NAND flash storage type.
MLC contains two bits in each cell. Since erasures and writings occur twice as frequently, MLC has less stamina compared to SLC.
TLC stores three bits in each cell, or triple-level cells. Many consumer-level products will use this as it is less expensive, though less performing.
Four bits are contained in each cell by QLC or quad-level cells. PLCs have much less durability and are therefore less expensive.
NAND flash shortage
In 2016, a flash shortage of NAND started. The shortage is partly the result of demand, but it is also due to the shift of vendors from 2D or planar NAND manufacturing to much denser 3D NAND technology. Making 3D NAND chips is a trickier process.
NAND flash vs. NOR flash
NAND and NOR flash memory are the two main types of flash, which get their names from their respective logic gates. NAND flash memory is written and read in blocks smaller than the computer, while NOR flash memory reads and automatically creates bytes. NOR and NAND flash memory use cases include laptop and desktop computers, digital cameras and audio players, manufacturing, and medical electronics.
Where is it used?
NAND is primarily found in memory cards, USB flash drives, and solid-state drives. NAND Flash is all around us – in our smartphones, on modern televisions, and on the computers and tablets in our homes and offices. It is also found outside, in all sorts of equipment from traffic lights to digital advertising panels, passenger announcement systems, and displays. Anything that has artificial intelligence (AI) and needs to transfer and retain data is likely to contain NAND Flash.
NAND Flash is available in different grades; industrial and consumer. There are significant differences between industrial and consumer-grade NAND, so it is important to consider the impacts these differences have on reliability, endurance, compliance, and total cost of ownership (TCO) before selecting the NAND Flash that is fit for purpose in your application.
Why is it used?
Devices made using NAND Flash offer mechanical shock resistance, and high durability and can withstand high pressure and temperature when compared to traditional hard disk drives. There are no moving parts, unlike HDDs, so are ideal for systems that vibrate and shake. NAND also offers fast read access times which is crucial when processing lots of data.
What are its limitations?
NAND has a finite number of reading/write cycles in a specific block (each time a bit is written or erased constitutes a program/erase cycle). Once a device reaches the user and is in operation (following manufacturer early life failure tests) its first day is always its best. NAND failure is inevitable once the program erases the cycle limit is reached. Individual cells fail and overall performance degrades, a concept known as wear-out.
Why is wear-out important?
When the NAND fails the device becomes unusable, resulting in the loss of data and application functionality.
How can I prevent this from happening?
The simple answer is you can’t! Advanced wear-leveling, overprovisioning, and firmware algorithms, can all help to increase NAND endurance. However, the best method is to understand your data usage and what the limitations are of each type of NAND used. Together with endurance technology you can protect your application’s functionality and data.
How is NAND made?
The way that NAND Flash is made can have a dramatic outcome on the performance characteristics.
NAND Flash goes through over 800 different manufacturing processes and it takes around 30 days to make just one wafer which is the size of a large pizza, typically 300mm in diameter. NAND factories or ‘FABS’ are huge, run 24/7, 365 days a year for maximum efficiency, and are 100 times cleaner than a hospital operating theatres. FABS can make different types of NAND Flash (SLC, MLC, 3D LTC – more on that below) and come in different sizes. Some of the largest FABS can make over 100,000 wafers a month.
Once the wafer is divided, or cut into separate chips, these are analyzed and graded as 1,2,3, or 4, with 1 being the highest quality. The chips are then shipped to a vendor, such as Kingston Technology, who uses the NAND in their products. The highest quality chips will have the best performance characteristics and therefore a price premium.
