Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

RAM cells need constant refreshing, however NAND FLASH cells can retain data for years together. What makes this possible ?

share|improve this question
Not all RAM cells need constant refreshing. – Ignacio Vazquez-Abrams Apr 28 '14 at 9:49

What makes NAND memories non-volatile is that the logic state is retained in a physical state that doesn't depend on the supply voltage.

For EEPROM memories in general (including Flash), this is a charge trapped in a floating gate.

share|improve this answer

As clabacchio pointed out, NAND flash memories can stores information in an array of memory cells made from Floating-gate MOSFET. Also some newer flash memory(included NAND memories) has a new technology. it's Multi-level cell.

I think these links will be very helpful and useful:

How Does Flash Memory Work?


How Flash Memory Works

Note: I know that they have spoken about Flash memory in these links but the technology that they have spoken about it is NAND type.

share|improve this answer

Also note that data retention is usually guaranteed for a period, e.g. 10 years. Also note that bit flipping can occur. SD cards for example usually have ECC built in to correct this, to some extent.

share|improve this answer
While true this doesn't really answer the question of how they work, as opposed to the implications of using FLASH memory. – PeterJ Jun 4 '14 at 1:39

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.