MRAM vs SRAM vs DRAMDifference between
MRAM,SRAM and DRAM
This page compares MRAM vs SRAM vs DRAM and
mentions difference between MRAM, SRAM and
DRAM. MRAM stands for Magnetoresistive RAM, SRAM
stands for Static RAM and DRAM stands for Dynamic
RAM. RAM stands for Random Access Memory.
MRAM-Magnetoresistive RAM
The term MRAM is the short form of Magnetoresistive
Random Access Memory. Unlike semiconductor memories
which use electron charge to store the data, MRAM uses
magnetic elements to store the data. It uses electron spin
which is inherently permanent unlike charge.
MRAM combines speed of SRAM, density of DRAM and
non-volatility of flash memory and hence it is often called
ideal memory.
The figure-2 depicts classical MRAM. As shown each bit
has spin dependent tunnel junction memory cell and
magnetic row and column write lines. The spin dependent
tunnel junction produces a large change in resistance
depending on predominant electron spin in a storage
layer. The tunnel barrier is as thin as a few atomic layers. It
depends on spin polarizations. Due to this, electrons can
tunnel through the normally insulating material which
causes change in resistance.
Hence in MRAM data is read as the tunnel junction
resistance while data is stored in the spin polarization of a
tunnel junction magnetic layer. The write lines create
magnetic fields which store data bits by setting magnetic
spin polarization.
Typically, the low resistance state is taken as logic-0 and
high resistance state is taken as logic-1.
As explained above,
• Magnetic cells are used to store the data.
• Reading is done by measuring the resistance of the cell
being read. MAgnetic tunnel effect alters the resistance of
the cell based on orientation of magnetic fields in the
surrounding plates.
• Writing is done in a number of ways. Earliest method
was to simply use induced magnetic fields to change the
fields of the plates. Writing has evolved into numerous
methods dependent on applications and resources
available.
Implementation of MRAM involves number of underlying
methods and technologies as mentioned below.
• Toggle mode
• Spin-transfer torque
• Thermal assisted switching
The next generation MRAM technologies could further
reduce the cell size and power consumption.
SRAM-Static RAM
• SRAM is the short form of Static Random Access
Memory.
• Array of storage cells used to implement static RAM.
Information is stored in latches.
• Following are features of Storage Cell.
-SR Latch
-Select input for control
-Dual Rail Data: Inputs B and B
-Dual Rail Data: Outputs C and C
DRAM-Dynamic RAM
• DRAM is the short form of Dynamic Random Access
Memory.
• Basic Principle: Storage of information on capacitors.
Charge leaks off and hence periodic refresh of charge is
needed.
• Charge and discharge of capacitor to change stored
value.
• Use of transistor as "switch" to:
-Store charge
-Charge or discharge
DRAM types are as follows:
• Synchronous DRAM (i.e. SDRAM)
• Double Data Rate DRAM (i.e. DDR DRAM)
• RAMBUS DRAM (RDRAM)
Comparison between MRAM,SRAM and
DRAM
Following table mentions comparison between MRAM,
SRAM and DRAM memory types.
Specifications
MRAM
SRAM
DRAM
volatile
NO
YES
YES
Speed
Fast
Fastest
Medium
Power consumption
Lowest
Medium
High
Density
Medium
Low
High
Infinite durability
YES
YES
YES
Following points mention comparison between MRAM and
SRAM:
➨MRAM is slightly slower than SRAM but still remains
competitive enough in speed.
➨SRAM has more complex design while MRAM is higher in
density.
➨MRAM is non-volatile while SRAM is volatile and will lose
the data without the power.
Following points mention comparison between MRAM and
DRAM:
➨MRAM performs faster read/write compare to DRAM
which requires capacitor charge/discharge.
➨Both MRAM and DRAM feature similar densities.
➨MRAM is non-volatile unlike DRAM.
➨MRAM has lower cell leakage.
➨MRAM has lower voltage requirements compare to
DRAM, which refresh its data often.
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