MRAM (MagnetoResistive Random Access Memory) By : Dhruv Dani - - PowerPoint PPT Presentation
MRAM (MagnetoResistive Random Access Memory) By : Dhruv Dani 200601163 Shitij Kumar 200601084 Team - N Flow of Presentation Current Memory Technologies Riddles Introduction Principle, Structure and Working Working Modes
By : Dhruv Dani 200601163 Shitij Kumar 200601084 Team - N
(MagnetoResistive Random Access Memory)
Current Memory Technologies Riddles Introduction Principle, Structure and Working Working Modes Schematic Overview MRAM v/s Other Memory Elements Applications in Embedded Systems Case Studies Supported Microcontrollers and Companies Constraints References
Volatile
increase of idle time.
Non -Volatile
Commonly Known Memories
A car component manufacturing company ‘X’ has to built Air Bag
systems for a range of cars.
The requisites of building such a system are that it has to interact
with the various sensors which detect and record passenger weight and are employed in other safety devices on the vehicle which perform various crucial tasks like detecting the impact of the possible collision.
Such a real time system requires the memory to be susceptible to
continuous reads, writes and overwrites in each clocked interval.
As an embedded engineer for this company X which kind of
memory would you use to implement such a system?
The Defense Research and Development Organization of a nation
‘C’ has to build a system which can be employed by them for their military and aerospace applications.
These systems at present require constant power supply to
maintain various kinds databases consisting of confidential information.
The battery generally acts as the power supply and is entrusted to
keep the information accessible and safe at all times.
But it has been experienced day in and day out that systems which
use battery back-up have an inherent reliability problem.
As an embedded engineer what modifications would you do to
such a system?
Magneto-resistive RAM, or Magnetic RAM is a form of
non-volatile RAM memory technology that uses magnetic charges to store data instead of electric charges.
In the early 1990’s the company Honeywell
conceived a new class of Magnetoresistence memory devices which offered promise for high density, random access and non–volatile memory.
Commercially, the first mass production of
MRAMS was started by Freescale – Everspin.
Principle
an effect known as Magnetoresistance.
measured on the basis of the magnetic moment of the inherent layers of the MRAM.
MRAM is constituted of various storage elements called
Magnetic Tunnel Junctions (MTJ) integrated with CMOS processing.
Each MTJ is composed of two layers (ferromagnetic plates),
fixed and free separated by a thin dielectric material.
Fixed layer : Magnetic polarity is fixed Free Layer : Magnetic polarity is subject
to change in accordance with the magnetic field which is the resultant of the applied current.
When a bias is applied to the MTJ, electrons that are spin polarized by
the magnetic layers traverse the dielectric barrier through a process known as tunneling.
The MTJ device has a low resistance when the magnetic moment of the
free layer is parallel to the fixed layer and a high resistance when the free layer moment is oriented anti-parallel to the fixed layer moment.
The data is stored as a magnetic state rather than a charge, and sensed by
measuring the resistance without disturbing the magnetic state.
The magnetic polarization does not leak away with time like charge
does, so the information is stored even when the power is turned off.
Switching the magnetic polarization between the two states does not
involve actual movement of electrons or atoms, and thus no known wear-out mechanism exists.
Write Mode
digit line and a bit line, writing only the bit at the cross point
Read Mode
turned on to bias the MTJ, and the resulting current is compared to a reference to determine if the resistance state is low or high using the sense line.
Flash - Continuous writes can wear out some flash
memories in 10 days. Meanwhile, MRAM can endure infinite write cycles because no charging or discharging is involved. Rotation of magnetic polarities during , is a non-destructive and non - degrading operation. MRAM uses current that creates a magnetic field to program the free layer. Furthermore, flash performs a write or erase operation on a large block of the memory array. MRAM perform writes on individual addresses.
SRAM - It requires power to retain memory contents.
MRAM memory contents are held in the polarity of its free magnetic layer. Since it is magnetic, this layer retains its state even without power. The leakage effect comes into the picture in the case of SRAMs technologies shrink. Given MRAM's non-volatility, power down techniques can be used in the system for zero current leakage.
Battery – Backed SRAM - This consists of an SRAM unit
and an accompanying battery in the same package to make it non - volatile. Meanwhile, MRAM performs read/ write at a speed faster than battery-backed SRAM. This improves reliability and dismisses environmental issues linked with battery disposal.
EEPROM:This standalone memory has much slower
programming speeds compared with MRAM, and limited write-cycling capability.
DRAM: Memory has to be frequently refreshed to retain
data because capacitors are used to store the data and there is a continuous charge leakage. So more power is used.
FRAM: Ferroelectric RAM (FRAM) is non - volatile has
typical small array sizes ranging from 4Kbit to 1Mbit. The array sizes are small because this technology has limited
programmed faster than FRAM.
Data Storage Industrial Automation Gaming Energy Management Communication Transportation
Automotive applications using sensors can benefit from
memories have difficulty keeping up with such data flow. New airbag systems also have sensors to detect and record passenger weight, interactions with other safety devices on the vehicle and the impact of collision.
Other automotive systems such as odometers, tire pressure
log and ABS require frequent writes to memory that easily exceed the write-erase capabilities of flash and wear out its
a more reliable system for mission-critical devices such as airbags and ABS.
The use of MRAM in the military is also gaining wide
have inherent reliability issues with battery use.
We have already seen that MRAMS are faster than battery
backed SRAMs and are more environment friendly.
On similar grounds we feel that in future years MRAM can
be integrated with a GPS to replace its inherent battery – backed memory.
Rad – Hard MCS8051 instruction-compatible microcontrollers (MCUs)
that can directly interface with Honeywell's new HXNV-0100 64k x 16 radiation-hardened Magnetic RAM (mram).
Most readily available MRAM – Freescale’s MR2A16A.
IBM, Motorola, Infineon Technologies, Sony, HP
, NVE Corporation are some other manufacturers.
Renesas Technologies Plans to Launch MCU with Embedded MRAM in
2008, use MRAM to provide unified memory for MCUs
Power Efficiency
Size
Manufacturing
magnetic device varies exponentially with the thickness.
Cost
www.everspin.com/technology.html - TSP – 12545_MRAM.pdf http://www.industrial-embedded.com http://www.nve-spintronics.com/mram-operation.php http://www.mram-info.com/ http://www.eetasia.com Freescale Semiconductor Datasheet – MR2A16A http://www.scribd.com/doc/13178752/Magneto-Resistive-RAM-or-MRAM http://www.freescale.com/files/memory/doc/fact_sheet/MRAMTECHFS.p
df
http://www.radio-electronics.com/info/data/semicond/memory/mram-
memory-technology.php
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