There are 3 types of NAND flash, SLC, MLC and TLC. SLC is first invented by Toshiba in 1987, but it has only small capacity and very expensive, usually use in thumb drive. After that MLC with higher capacity and lower cost was invented, but it is still expensive compare to HDD, so it is only used in enterprise level or high-end consumer. Finally, TLC came to the market, it has even higher capacity and an acceptable price for normal consumer. People start to use it in computer, mobile phone and other consumer product.
SLC: Single-Level Cell, store 1-bit data per cell
MLC: Multi-Level Cell, store 2-bit data per cell
TLC: Trinary-Level Cell or 3-bit MLC, store 3-bit data per cell
How NAND flash works?
There is a silicon dioxide on each cell, it works as a cap of the cell, to prevent electron going in or coming out accidentally. When writing data, voltage will be increased to let electron pass through the silicon dioxide into the cell. To erase data, voltage will be increased again so electron can leave the cell by passing through silicon dioxide again.
As TLC can store 3bit data, it needs 8 different level of voltage to allow different number of electrons into the cell.
Performance: SLC > MLC > TLC
To read or write data, SLC is very simple, only 0 or 1, therefore SLC is the fastest. MLC has 4 different electron level, performance is slower than SLC. As for TLC, it has 8 different level, so it takes more time to determine the electron level. And sometimes there will be mistake when operating, therefore TLC need extra error correction to make sure the data is correct.
Life Endurance: SLC > MLC > TLC
SLC has up to 100,000 erase cycles, MLC has 5,000~10,000 erase cycles, but TLC has only less than 3,000 erase cycles.
It is due to TLC need 8 different voltage level and it can store more bits in single cell, the usage for electrons to pass through the silicon dioxide is much more frequent, it makes silicon dioxide layer wear out faster. Therefore, the life endurance for TLC is much shorter.
Capacity: SLC < MLC < TLC
TLC can store 3bit data in single cell, therefore compare SLC and TLC in the same chip size, TLC can store more data than SLC. It makes capacity of SSD getting closer to HDD.
Reliability: SLC > MLC > TLC
SLC only has 2 electron level, it is very easy to read and write. MLC and TLC have more than 2 electron level, especially for TLC, there are 8 different electron level, as the differences between each level are very small, error may occur when writing data. Therefore, SLC has the highest reliability compare to MLC and TLC.
Kogen works with top Taiwan ODM factory to provide SSD with all kinds of NAND flash depend on customer application. For industrial or military application, we recommend MLC and SLC to get best life endurance and reliability. For consumer product, we recommend TLC for more competitive price and higher capacity.
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