magnetic ram (ashley jefferson)

7/30/2019 Magnetic RAM (Ashley Jefferson)

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Magnetic RAM

By: Ashley Jefferson

a.k.a Magnetoresistive Random Access Memory


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What is Magnetic RAM?

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.
http://en.wikipedia.org/wiki/Random_Access_Memoryhttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Magnetismhttp://en.wikipedia.org/wiki/Magnetismhttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Random_Access_Memory


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Magnetic RAM ArchitectureShows how MRAM reads and writes

Credit: http://domino.research.ibm.com
http://domino.research.ibm.com/http://domino.research.ibm.com/http://domino.research.ibm.com/comm/pr.nsf/pages/rscd.mramimages-picf.html


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What is Magnetic RAM? How

does it work? 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 insulatinglayer

One of the two plates is a permanent magnet set to a

particular polarity, the other's field will change to matchthat of an external field. A memory device is built from a

grid of such "cells".


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An image of the layers involved

in an MRAM storage device.

Credit: http://domino.research.ibm.com
http://domino.research.ibm.com/http://domino.research.ibm.com/http://domino.research.ibm.com/comm/pr.nsf/pages/rscd.mramvlsi-1.html


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How does it work?

MRAM works like the read/write head of ahard drive.

But unlike a hard drive, which includesmechanical parts (the moving arm holdingthe read/write head and the rotating plates

on which the information is stored), MRAMis a solid state device and, as such, hasmuch greater speed and durability


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How does it Read?

An MRAM chip reads information by measuring theelectrical resistance of a specific cell that, in turn,depends upon the alignment of the magnetic momentsof the layers of the cell.

To read a bit of information, a current is passedthrough the memory cell.

If the magnetic moments are in a parallel orientation,then the detected resistance would be smaller than ifthey were in an anti-parallel orientation.


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Diagram of Read Process

Credit: http://www.tfot.info/
http://www.tfot.info/http://www.tfot.info/


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How does it Write?

Write is achieved by the alignment of the magneticmoments of the two memory layers into one or theother relative orientation.

Current is passed through two sets of parallel wiresor write lines (called a bit line and a digit or wordline), which pass over and beneath the memory

cells, respectively

To write to a particular memory cell (bit), currentis passed through the two wires that intersect at

that memory cell.


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Diagram of Write Process



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Advantages of Magnetic RAM

MRAM has been called the ideal memory-

potentially combining the density of DRAM with the

speed of SRAM and non-volatility of Flash memory

or hard disk, and all the while consuming a very low

amount of energy

MRAM has much faster write speeds than Flash and

has an unlimited endurance, meaning that MRAM is

not subject to the degradation suffered by Flash.


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Advantages of MRAM

MRAM can resist high radiation, and can operate inextreme temperature conditions. It is likely that wellsee the first MRAM in applications that need such

properties

Like Flash, MRAM retains data after a power supplyis cut off, potentially eliminating that seeminglyendless boot time of conventional computers when

data from the hard drive is transferred to RAM, aswell as loss of data when the computer is suddenlyshut off.


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Advantages of MRAM

The magnetic architecture of the chip can bereprogrammed on a whim and its adaptability couldmake it very popular with manufacturers of special-

purpose computing hardware, from video-gameplatforms to medical diagnostic equipment.

The chip's nanomagnets -- on the order of 110nanometers wide -- can be assembled into arrays that

mirror the function of transistor-based logic gates inaddition to storing information. These logic gates arethe building blocks of computer technology, givingmicrochips the power to process the endless rivers of

binary code.


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Advantages of MRAM

Using a magnetic state for storage has two main

benefits:

1) the magnetic polarization does not leak away withtime like charge does, so the information is stored

even when the power is turned off; and

2) switching the magnetic polarization between the

two states does not involve actual movement ofelectrons or atoms and thus has no known wear-out

mechanism.


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Disadvantages of Magnetic RAM

Is (currently) expensive

Power consumption of MRAM technology

is still high

Freescales MRAM technology only holds

4M. So it cant currently be widely used


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Comparison Table



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What is MRAM going to be

used for? Proposed uses for MRAM include devices such

as:

Aerospaceand military systems Digital Cameras

Notebooks

Smart Cards

Mobile Telephones

Cellular base stations

Personal Computers


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Is it available today?

Although MRAM has many advantages over virtually every existingmemory type, it is still in its infancy.

Many had hoped MRAM would usher in the age of instant-on

computers able to replace the computer main memory and harddrives, but, due mainly to its cost, these hopes remain a dream

Even though many large companies such as IBM, Intel and HP, areworking on MRAM,Only two vendors have succeeded in bringingMRAM parts to the mass market - Cypress and Freescale.

Cypress, however, has discontinued their offering shortly afterrelease


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Is it available today?

In February, Toshiba and NEC announced a 16 Mbit MRAMchip with a new "power-forking" design. It achieves a transferrate of 200 MB/s, with a 34 ns cycle time - the best

performance of any MRAM chip. It also boasts the smallest

physical size in its class -- 78.5 square millimeters -- and a lowpower requirement of 1.8 volts.

In July 2006, Freescale started selling the first commercialMRAM module, with 4Mbit of memory, for $25 a piece.

This is still very expensive and low density, and probably suitsa very small list of select customers. A realistic timeframe for acell phone with MRAM or a MRAM-Disk-On-Key is probably2010 at least.

magnetic ram (ashley jefferson)

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