Flash drives use non-volatile flash memory to allow for portable data storage. They consist of a small circuit board with NAND flash memory chips, controllers, and a USB connector. Flash drives offer advantages over hard drives like smaller size, lighter weight, lower power consumption, and greater shock resistance. However, flash memory has a limited number of write/erase cycles and is more expensive per unit of storage than hard drives. Flash drives are commonly used to transfer files between computers and store data on devices like cameras, phones, and music players.

1. Flash Drives
Submitted by:
Animesh Shaw
Narula Institute of Technology

2. Content
INTRODUCTION
WHAT IS COMPUTER MEMORY ?
WHAT IS FLASH DRIVE ?
HISTORY
COMPOSITION
DESIGN AND IMPLEMENTATION
ESSENTIAL COMPONENTS
ADDITIONAL COMPONENTS
COMPARISON WITH OTHER DRIVES
USES OF FLASH DRIVE
ADVANTAGES
DISADVANTAGES
FUTURE ENHANCEMENTS

3. INTRODUCTION
A flash memory combines a number of older technologies
with the low cost ,low power consumption and small size
which is possible by recent advance in microprocessors
technology. These have a limited capacity and can be erased &
overwritten for many number of times ,they do require
complex high voltage drive circuitry.

4. What is Computer Memory?
Computer data storage, often called storage or memory, refers
to computer components, devices, and recording media that
retain digital data used for computing for some interval of time.
Computer data storage provides one of the core functions of the
modern computer, that of information retention.
 It is one of the fundamental components of all modern
computers, and coupled with a central processing unit (CPU, a
processor),implements the basic computer model used since the
1940s.

5. Types Of Storage
Primary storage, presently known as
memory, is the only one directly accessible
to the CPU. The CPU continuously reads
instructions stored there and executes
them.
Example..RAM
Secondary storage, or storage in popular
usage, differs from primary storage in that it
is not directly accessible by the CPU.
Example..Hard Disk, Flash Memory

6. Continue…
Static Memory
A form of volatile memory similar to DRAM with the exception that it does
not refresh on occasion.
Dynamic Memory
A form of volatile memory which also requires the stored information to be
periodically re-read and re-written, or refreshed, otherwise it would vanish.
 Volatile Memory
Requires constant power to maintain the stored information. Since primary
storage is required to be very fast, it predominantly uses volatile memory.
Non- Volatile Memory
Will retain the stored information even if it is not constantly supplied with
electric power. It is suitable for long-term storage of information.

8. What is Flash Memory ?
Flash memory, sometimes called flash RAM, is a type of
semiconductor device that combines important features of both
memory & storage. These features include high-speed access
and retention of data in the absence of a power supply.
Flash memory gets its name because the microchip is organized
so that a section of memory cells are erased in a single action or
"flash."
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.

10. HISTORY
In 2000 IBM first start selling pen drives in collaboration
with TREK technology.
The first Pen drive have the capacity of 8 MB.

11. COMPOSITION
•A flash drive consists of a small printed circuit board
protected by a plastic body
•A USB flash drive consists of a NAND-type flash memory
data storage device
•It consists of standard type- A USB connection allowing
plugging in the port of personal computer

12. DESIGN & IMPLEMENTATION
One end of the device is fitted with a USB connector
Its chip consist of a printed board with power circuits and
ICs mounted on it
It typically use the USB mass storage device class to
communicate with the host

13. ESSENTIAL COMPONENTS
A USB connector
Crystal oscillator -controls device
data output
Mass storage controller
containing microcontroller,
RAM & ROM
NAND flash memory chip-used
for storing data.
Mohd wasif (1 year,2nd semester)

14. ADDITIONAL COMPONENTS
Jumpers and test pins -for testing and loading codes into
the microprocessor
LEDs -indicates data transfer
Write protect switches -indicates whether the drive is in
“write protection” mode
USB connector cap

15. How Flash Memory Works?
It has a grid of columns and rows with a cell
that has two transistors at each intersection.
The two transistors are separated from each
other by a thin oxide layer. One of the
transistors is known as a floating gate, and
the other one is the control gate.
The floating gate's only link to the row, or
wordline, is through the control gate. As
long as this link is in place, the cell has a
value of 1.
To change the value to 0 requires a curious
process called Fowler-Nordheim
tunneling.

16. Flash Memory: Tunneling and Erasing
Tunneling is used to alter the placement of electrons in the
floating gate. An electrical charge, usually 10 to 13 volts, is
applied to the floating gate. The charge comes from the column,
or bitline, enters the floating gate and drains to a ground.
This charge causes the floating-gate transistor to act like an
electron gun. The excited electrons are pushed through and
trapped on other side of the thin oxide layer, giving it a negative
charge.
These negatively charged electrons act as a barrier between the
control gate and the floating gate.
A special device called a cell sensor monitors the level of the
charge passing through the floating gate.

17. Continue…
If the flow through the gate is above the 50 percent threshold, it has a
value of 1. When the charge passing through drops below the 50-
percent threshold, the value changes to 0. A blank EEPROM has all of
the gates fully open, giving each cell a value of 1.
The electrons in the cells of a flash-memory chip can be returned to
normal ("1") by the application of an electric field, a higher-voltage
charge.
Flash memory uses in-circuit wiring to apply the electric field either
to the entire chip or to predetermined sections known as blocks. This
erases the targeted area of the chip, which can then be rewritten.
Memory works much faster than traditional EEPROMs because
instead of erasing one byte at a time, it erases a block or the entire
chip, and then rewrites it.

18. Removable Flash Memory Cards
While your computer's BIOS chip is the
most common form of Flash memory,
removable solid-state storage devices
are also popular.
SmartMedia and CompactFlash cards
are both well-known, especially as
"electronic film" for digital cameras.
Other removable flash-memory
products include Sony's Memory Stick,
PCMCIA memory cards, and memory
cards for video game systems.

19. Continue…
As shown below, SmartMedia cards
are extremely simple. A plane
electrode is connected to the flash-
memory chip by bonding wires.
The flash-memory chip, plane
electrode and bonding wires are
embedded in a resin using a technique
called over-molded thin package
(OMTP).
This allows everything to be integrated
into a single package without the need
for soldering.
The OMTP module is glued to a base
card to create the actual card.

20. Comparison with other devices
Floppy
Optical media(CD & DVD)
Tape
External hard disc

21. USES OF PEN DRIVE
Personal data transport.
Booting operation system.
Audio players.
Music storage and marketing.

22. Advantage Of Flash Memory
The advantages of flash memory as compared with HDDs
are substantial.
 Smaller in size
 Light weight
Low power consumption
Longer life expectancy
Greatly improved shock resistance.

23. Disadvantage…
The main disadvantage at present is that the cost per unit of
storage capacity is still much higher than that for HDDs.
However, the gap is gradually narrowing.
In contrast to RAM and like all types of EEPROMs, it wears out
after a certain number of write and erase cycles. This is due to
the degradation of the insulating oxide layer around the
microscopic cells that are used to store data. Fortunately,
however, the number of cycles in most applications is sufficiently
low that this situation is not frequently encountered.
Bad Blocks

24. Applications
Flash memory is very useful in a
variety of applications including:
Your computer BIOS
Memory Cards
Mp3 players
Modems
Video game cards
Digital cellular phones
Digital cameras