Title: FERROELECTRIC RAM [FRAM]
1FERROELECTRIC RAMFRAM
- Presented by
- Javad.P
- N030
2- FEATURES OF FRAM
- 1.FRAM allows systems to retain information even
when power is lost i.e. non-volatile. - 2.The number of write cycles supported by the
FRAM components is - nearly unlimitedup to 10 billion read/writes.
- 3.Low power requirements.
- 4.When an electric field is applied to a
ferroelectric crystal, - the central atom moves in the direction of the
field. - 5.As the atom moves within the crystal, it passes
through an energy barrier, causing a charge
spike. - 6.Internal circuits sense the charge spike and
set the memory - If the electric field is removed from the
crystal, the central atom stays in position,
preserving the state of the memory. This - makes FRAM non-volatile, without any periodic
refresh. - 7.Once a cell is accessed for a read operation,
its data are presented in the form of an
analSignal to sense amplifier, where they are
compared against a reference voltage to findthe
logic level.
3BASIC MEMORY CELL STRUCTURE
Bitline(BL)
word line (WL)
Plateline(PL)
4- A ferroelectric memory cell, known as IT- IC (one
transistor, one capacitor) structure which is
similar to that of DRAM. - The difference is that ferroelectric film is
used as its storage capacitor rather than
paraelectric material as in DRAM. - Figure above shows memory cell structure,
consists of a single ferroelectric capacitor that
is connected to a Plateline(PL) at one end and,
via an access transistor, to a Bitline(BL) at the
other end. Raising the wordline (WL) and hence
turning ON the access transistor accesses the
cell.
5FERRO ELECTRIC CRYSTAL
Ferroelectric CrystaI The center atom moves to
store ones and zeros
- Consist of 8 atom of lead at corners
- 6 atom of oxygen at face centers
- 1 atom of titanium at cube centers
6FRAM TECHONOLOGY
- When an electric field is applied to a
ferroelectric crystal, the central atom moves in
the direction of the field. - As the atom moves within the crystal, it passes
through an energy barrier,causing a charge spike. - Internal circuits sense the charge spike and set
the memory. If the electric field is removed from
the crystal, the central atom stays in position,
preserving the state of the memory. - This makes FRAM non-volatile, without any
periodic refresh
7-
- An electric field is applied.
-
- If the atoms are near the cube "floors" and the
electric field pushes them to the top, the cell
gives off a current pulse. - This pulse, representing a stored 1 or 0, is
detected by a sense amplifier. If the atoms are
already near their cubes' "ceilings," they don't
budge when the field is applied and the cell
gives off a smaller pulse. - Reading an FRAM cell destroys the data stored in
its capacitor. So after the bit is read, the
sense amplifier writes the data back into the
cell, just as in a DRAM.
FRAM READ OPERATION
8FRAM WRITE OPERATION
- To write a "1" into the memory
cell, - the BL is raised to Vdd-
- Then the WL is raised to Vdd Vt.
- This allows a full Vdd to appear across the
ferroelectric capacitor - At this time the state of ferroelectric is
independent of its initial state. - Next, the PL is pulsed, WL stays activated until
- the PL is pulled down completely and the BL is
driven back to zero. - The final state of the capacitor is a negative
charge state S1. -
9To write a "0" into the cell
-
- the BL is driven to 0V prior to activating the
WL. - The rest of the operation is similar to that of
writing a "1 - The written data is held in the cell even though
the selection of the wordline is changed to non
selected state (i.e. transistor is OFF), so it is
nonvolatile.
10 FRAM AS RAM AND ROM
FRAM memory fills the RAM and ROM performance gap
- The key advantage to FRAM over DRAM is what
happens between the read and write cycles. In
DRAM, every cell must be periodically read and
then re-written, a process known as refresh.. - In contrast, FRAM only requires power when
actually reading or writing a cell. The vast
majority of power used in DRAM is used for
refresh power usage about 99 lower than DRAM.
11RAMTRON-FRAM
12COMPARISON
FRAM EEPROM Flash Memory DRAM SRAM
Memory Type Non-volatile Non-volatile Non-volatile Volatile Volatile
Read Cycle 100ns 200ns 120ns 70ns 85 ns .
Write Cycle 100ns 10ns 100ns 70ns 85ns
Power Consumption 1nJ lnJ 2nJ 4nJ 3nJ.
Current to retain Data Unnecessary Unnecessary Unnecessary' Necessary Necessary
Internal Write Voltage 2V-5V 14V 9V 3.3V 3.3V
Cell Structure 1T-1C 2T IT 1T-1C 6T,4TR
Area/Cell 4 3 1 2 4 -
13- ADVANTAGES
- FRAM allows systems to retain information even
when power is lost, without resorting to
batteries, EEPROM, or flash. - Access times are the same as for standard SRAM,
so there's no delay-at-write access as there is
for EEPROM or flash. - Low power consumption, low voltage operation and
high write endurance make it superior than
other non-volatile memories like EEPROM FLASH. - It is less expensive than magnetic memories.
14- DISADVANTAGES
- Present high cost.
- Low density compared to DRAM SRAM.
- FUTURE OF FRAM
- Increased memory capacity
- High density, to operate under very high
temperatures. - Combine FRAM with other logic technologies to
offer more enhanced devices.
15- APPLICATIONS
- Personal digital assistants (PDAs), handheld
phones, power meters, and smart card, and in
security systems - SMART CARDS USING FRAM
- Dial a connection on a mobile telephone and be
charged on a per-call basis - Establish your identity when logging on to an
Internet access provider or to an online bank - Pay for parking at parking meters or to get on
subways, trains, or buses - Give hospitals or doctors personal data without
filling out a form - Make small purchases at electronic stores on the
Web (a kind of cybercash) - Buy gasoline at a gasoline station
16CONCLUSION
- Ferroelectric memories are superior to EPROMs
Flash memories - in terms of write access time overall power
consumption.Two eg of - such applications are contactless smart cards
digital cameras. - Future personal wireless connectivity
applications that are battery - driven will demand large amounts of non volatile
storage to retain - accessed internet webpages, contain compressed
video, voice and - data. The density and energy efficiency of
writing data to memory - would seem to indicate that ferroelectric
memory will play a major role - in these types of consumer products.
17THANK YOU