© dsi confidential arithmetic operations within memristor-based analog memory mika laiho, eero...
Post on 20-Dec-2015
218 views
TRANSCRIPT
© DSI CONFIDENTIAL
Arithmetic Operations within Memristor-Based Analog Memory
Mika Laiho, Eero LehtonenMicroelectronics Laboratory, University of Turku
© DSI CONFIDENTIAL
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
© DSI CONFIDENTIAL
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
© DSI CONFIDENTIAL
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
© DSI CONFIDENTIAL
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
© DSI CONFIDENTIAL
Modeling Memristor
The window function
The time derivative of the state variable W
The current through the memristor
• 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
© DSI CONFIDENTIAL
Simulated Memristor Characteristics
Device simulation based on SPICE model
© DSI CONFIDENTIAL
Simulated Memristor Characteristics
Device simulation based on SPICE model
© DSI CONFIDENTIAL
Memristor Analog Memory/Computing Circuit
VSSR
© DSI CONFIDENTIAL
Memory/Computing Circuit Simulation
V1
Vin
Imem
Ir
CT
W
Circuit simulation based on SPICE model
© DSI CONFIDENTIAL
Processing as Summation
Monitoring phase Programming phase
gm1 = gm4 + gm5.
© DSI CONFIDENTIAL
Processing as Invertor
© DSI CONFIDENTIAL
Processing as Universal Addition
© DSI CONFIDENTIAL
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
© DSI CONFIDENTIAL
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