How does flash devices work?
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Transcript of How does flash devices work?
HOW DOES FLASH MEMORY WORK?
By Sarat Bhargavaee13b1008
Table of Contents
Introduction to Flash Memory.
The Basic Storage element of a Flash Storage devices
How to read, write, erase data to a Floating gate Transistor(FGT) ?
Comparison between NOR and NAND architectures.
How to read , write , erase data in each of NOR , NAND architectures ?
Introduction to Flash Memory
What is Flash Memory ?
Flash memory belongs to the class of Electronic Non-volatile memories.
It was first introduced by Toshiba in 1984.
There are mainly 2 Types of Flash memory technologies• Nand Flash • Nor Flash
Floating-gate Transistor
The basic storage element of Flash memory is Floating gate Transistor.
Floating gate Transistor MOSFET
The Floating gate is electrically insulated on all sides
SLC (Single level cell)
MLC (Multi level cell)
Reading from Floating gate transistor
Writing to a Floating gate transistor
How to change the charge stored in Floating gate when it is electrically isolated ?
Hot electron injection
In this process we apply Very High Voltage (5V) at the Control gate
and across the Source and drain.
Quantum Tunnelling
In this process we apply very high Negative Voltage across the control gate
and the source.(Erasing making 1’s).
Very high Positive across Cg , Source for programming.
NOR and NAND Architectures
FGT’s are connected in parallel in NOR architecture
Have Low latency time or High read speed. Less bit density Used in places where Random access is
required
FGT’s are connected in series (8) Writing speed is much faster than
NOR at the cost relatively high latency.
More bit density Used in USB devices
Reading data
NOR Architecture:NAND Architecture:
Erasing data
NOR Architecture: NAND Architecture:
Writing data
NOR Architecture:NAND Architecture:
Conclusion
Now a days the flash memory technology is trying to replace the traditional Hard drives with SSD’s because of low latency and low power consumption.
But the challenge is the cost
In recent times there are attempts to replace them with DRAM.
But here the challenge the low access speed compared to DRAM.
Sources
http://en.wikipedia.org/wiki/Flash_memory#cite_note-32
https://www.youtube.com/watch?v=s7JLXs5es7I&index=211&list=WL
http://images.google.co.in/