welcome. SEMINAR ON…. magnetic random access memory ( mram ). Why can’t your pc simply turn on like your television? MRAM uses magnetism rather than electrical power to store bits of data. No refresh is needed to retain the data. For users of laptops and other mobile
MRAM uses magnetism rather than electrical power to store bits of data.
No refresh is needed to retain the data.
For users of laptops and other mobile
devices, such as MP3 players and cell phones,
MRAM is the holy grail of longer battery life.
MRAM is on the path to become the universal memory to replace DRAM, SRAM and Flash memory.
MRAM is the enabling technology for computer systems on a single chip.
MRAM Promises to be,
Low power alternative
MRAM uses magnetic cells to store data.
Because magnetic memory cells maintain their
state even when power is removed
MRAM possesses a distinct advantages over electrical.
MRAM threatens to replace not only DRAM, but also
Because it is much faster to write on to MRAM.
which uses magnetic storage & magneto resistance(MR) to read the stored data.
MRAM is memory technology that uses electron spin to store information.
Unlike conventional RAM chip technologies, data is not stored as electric charge or current flows, but by magnetic storage elements.
MRAM has been called "the ideal memory“
MRAM can resist high radiation, and can operate in extreme temperature conditions, very suited for military and space applications.
An MRAM chip is made up of millions of pairs of tiny ferromagnetic plates (like the one covering hard drives) called memory cells, i.e., magnetic sandwiches consisting of two magnetic layers separated by a very thin insulating layer.
One of the two plates is a permanent magnet set to a particular polarity, the other's field will change to match that of an external field. A memory device is built from a grid of such "cells".
Like Flash memory, MRAM is a nonvolatile memory--- a solid-state chip that has no moving parts.
Unlike with DRAM chips, you don’t have to continuously refresh the data on solid state chips.
Flash memory can’t be used for instant-on PC’s because it hasn’t demonstrated long-term reliability.
MRAM will likely compete with Flash memory in the portable device market for the same reason that it will replace DRAM –it reduces power consumption.
2-D Management Write Selection.
2. 1-D Management Write Selection.
Early magnetic random access memory (as opposed to serial memories like tape and disk) used the natural hysteresis of magnetic materials to store data (‘1” or “0”) by using two or more current carrying wires or straps.
Most of today’s MRAM concepts still use this write selection technique
Ix,Iy together switch the cell
Ix,Iy Alone Doesn’t Switch Cell
In this new scheme, a select transistor per memory cell is used for writing and a much smaller current is used for reading than for writing.
This should result in substantially wider process margins, but probably at the sacrifice of density due to the size of the required transistor in the cell.
. This “1D magnetic select" scheme is potentially ideal for small, high performance nonvolatile RAM .
The transistor provide the selection of the memory cell and not the magnetic switching properties of the cell.
A very large current can be used to write and a small current can be used to read the cell, thus providing potentially very large margins.
Inductive readout scheme
Magnetoresistive readout scheme
A current through the stripe magnetized the NiFe clockwise or counterclockwise when aided by a current (field) from an orthogonal strip line
Current in either strip by itself would not change the storage state. Thus, a single memory cell could be selectively written in a 2D array.
Despite improvements in reading methods , the maximum differential resistance of the cell between a “1” and a “0” when it was read was about ¼ of the 2% magneto resistance, or about 0.5%.
In real arrays with practical sense currents, this gave differential sense signals of 0.5 to 1.0 mV
A Giant Magneto resistance was discovered in 1988 independently by Baibich et al. in Paris and Binasch et al.in Jülich.
It is the phenomenon where the resistance of certain materials drops dramatically as a magnetic field is applied
It is described as Giant since it is a much larger effect than had ever been previously seen in metals.
The memory arrays in these memories sense relatively small signals (1mv) , leading to a read access time of about 250 ns.
GMR materials showed a magneto resistance ratio of about 6% .Since the read access times tends to improve as the square of the signal, normal scaling would indicate that the improvement of a factor of 3 in magneto resistance would lead to a 9 times improvement in read access time.
The competition – semiconductor memory – was still faster because of the low MRAM sense signal.
Due to exchange, there are limits to how quickly the magnetization can change directions with distance, and near the center of a 1 micron stripe, the magnetizations of the two magnetic layers in the sandwich would be directed substantially along the stripe, thus storing data very marginally.
The electrically erasable programmable read only memory boasts fast, unlimited readout. However, the write cycle is very slow (10 msec), requires high voltages, and can only be done 10 5 times before the memory fails.
Like EEPROM, most flash memories require high voltage for writing and has low cycling endurance, 10 6 cycles. At 5 to 10 msec, the write speed is considerable faster than EEPROM
Unlimited cycling endurance and high speed read and write are key advantages of MRAM over most other nonvolatile technologies
MRAM is intrinsically radiation immune and can also be used in high temperature applications.
MRAM has potential in all memory applications
Finally, the storing of use data for word addresses could be done in MRAM, once again extending the life of the system.
The Future of MRAMExpected to Replace SRAM, DRAM, & FLASHPredicted to be the Memory Standard in both Computers & Consumer Electronics
MRAM will become the standard memory for the next couple of year
MRAM will be use in other devices