Multi-level cell: Difference between revisions

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{{short description|Memory cell capable of storing more than a single bit of information}}

In [[electronics]], a '''multi-level cell''' ('''MLC''') is a [[memory cell (computing)|memory cell]] capable of storing more than a single [[bit]] of information, compared to a '''single-level cell''' ('''SLC'''), which can store only one bit per memory cell. A memory cell typically consists of a single [[floating -gate [[MOSFET]] (metal-oxide-semiconductormetal–oxide–semiconductor field-effect transistor), thus multi-level cells reduce the number of MOSFETs required to store the same amount of data as single-level cells.

'''Triple-level cells''' ('''TLC''') and '''quad-level cells''' ('''QLC''') are versions of MLC memory, which can store three and four bits per cell, respectively. The name "''multi''-level cell" is sometimes used specifically to refer to the "''two''-level cell". Overall, the memories are named as follows:

# Single-Levellevel Cellcell or SLC (1 bit per cell)

# Multi-Levellevel Cellcell or MLC (2 bits per cell), alternatively Doubledouble-Levellevel Cellcell or DLC

# Triple-Levellevel Cellcell or TLC (3 bits per cell) or 3-Bit MLC

# Quad-Levellevel Cellcell or QLC (4 bits per cell)

# Penta-Levellevel Cellcell or PLC (5 bits per cell) – currently in development

Typically, as the '"level'" count increases, performance (speed and reliability) and consumer cost decrease; however, this correlation can vary between manufacturers.

Examples of MLC memories are MLC [[NAND flash]], MLC PCM ([[phase -change memory]]), etc. For example, in SLC NAND flash technology, each cell can exist in one of the two states, storing one bit of information per cell. Most MLC NAND [[flash memory]] has four possible states per cell, so it can store two bits of information per cell. This reduces the amount of margin separating the states and results in the possibility of more errors. Multi-level cells whichthat are designed for low error rates are sometimes called '''enterprise MLC''' ('''eMLC''').

New technologies, such as multi-level cells and 3D Flash, and increased production volumes will continue to bring prices down.<ref>{{cite web |url=https://www.hyperstone.com/en/NAND-Flash-is-displacing-hard-disk-drives-1249,12728.html |title=NAND Flash is Displacing Hard Disk Drives |access-date=29 May 2018 }}</ref>