MRAM vs SRAM vs DRAM-Difference 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.
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 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.
-Select input for control
-Dual Rail Data: Inputs B and B
-Dual Rail Data: Outputs C and C
• 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:
-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.
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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