How long is the life of flash memory?

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nvd

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What is the life of flash memory. Are bad sectors possible in this type of memory?
 

Re: Flash memory


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    nvd

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Re: Flash memory

hi,
Flash memory refers to a particular type of EEPROM, or Electronically Erasable Programmable Read Only Memory. It is a memory chip that maintains stored information without requiring a power source.

Flash memory differs from EEPROM in that EEPROM erases its content one byte at a time. This makes it slow to update. Flash memory can erase its data in entire blocks, making it a preferable technology for applications that require frequent updating of large amounts of data as in the case of a memory stick.

Inside the flash chip, information is stored in cells. A floating gate protects the data written in each cell. Tunneling electrons pass through a low conductive material to change the electronic charge of the gate in "a flash," clearing the cell of its contents so that it can be rewritten. This is how flash memory gets its name.
 

Re: Flash memory

Flash memory utilizes direct tunneling in NAND type flash memory and hot electron in NOR type flash memory. To do this flash memory cells require high voltages. The required voltage level in NAND type is higher than in NOR type because NAND type utilizes direct tunneling. This kind of stress degrade the dielectric quality in flash memory. (Even in just COMS logic gate the switching degrade the dielectric quality) After a number of read/write cycles, when large amount of carriers are trapped in dielectric or some defects grow up, the memory cell can not guarantee the correct data due to the Vt change or leakage, which is the life of flash memory.

In spec, NAND type allow 1 or 2bit error but NOR type doesn't. So NAND type memory uses ECC (error correction code) to recover the bit error.

It is possible to have some bad sectors but they should be controlled by controller (like hard disk).
 

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