Transcript Slides
Arithmetic Operations within
Memristor-Based Analog Memory
Mika Laiho, Eero Lehtonen
Microelectronics Laboratory, University of Turku
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Key Points
Be able to program the memristor to the
reference resistance using the cyclincally
programming scheme
Computing capability, such as addition,
both on negative and positive analog
conductance, is demonstrated
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Digital Memory verse Analog Memory
Digital memory (1-bit information
depending on ON/OFF state, including
SRAM, DRAM, PCRAM, MRAM, Flash, etc.)
Analog memory (many intermediate states
between ON/OFF states)
Memoristor can be used for both digital
and analog memory
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Memristor
Without programming threshold
–
–
–
Linearly programmed with charge flowing through
the device
AC readout for memory application
Pose high requirements on R/W cycles
With programming threshold
–
–
Nonlinear programmed with charge flowing
through the device
DC readout possible
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Memristor With Programming Threshold
Bipolar reversible and nonvolatile switching of nanoscale TiO2-x devices
J. J. Yang et al., Memristor switching mechanism for metal/oxide/metal nanodevices, Nature Nanotechnology, 2008, 3, 429-433
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Modeling Memristor
The current through the memristor
The time derivative of the state variable W
The window function
• ᵅ and ᵝ are fitting constants that are used to characterize the ON state
• ᵡ and ᵞ are the fitting constants used to characterize the net electronic barrier
when the memristor is switched OFF
• a, b, p and q are constants depending on the physical properties of the memristor
• w is the state variable of the memristor
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Simulated Memristor Characteristics
Device simulation based on SPICE model
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Simulated Memristor Characteristics
Device simulation based on SPICE model
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Memristor Analog Memory/Computing Circuit
VSSR
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Memory/Computing Circuit Simulation
V1
CT
Vin
Imem
W
Ir
Circuit simulation based on SPICE model
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Processing as Summation
Programming phase
Monitoring phase
gm1 = gm4 + gm5.
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Processing as Invertor
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Processing as Universal Addition
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Conclusions
Memristors could be used as analog
memories and for computing
A two-memristor configuration was
proposed to be used as a memory element
so that addition operations of both positive
and negative numbers could be performed
Further study on performing multiplication
and division is expected
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Limitations
Control circuits for programming the
memristors is too complicated increasing
design complexity
Many sequences are required leading to
slow programming
The programming time is unpredictable
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