Instrumentation • Electronics
4 With manufacturers striving to extract more performance from electronic devices, there is an accelerating trend towards alternative types of memory. Paul Stevens considers magnetoresistive random access memory (MRAM) and some of this technology’s variants.
4 Les efforts des fabricants pour mettre au point des produits électroniques toujours plus performants s’accompagnent d’une tendance croissante parmi les types de mémoire alternatifs. Paul Stevens prend en considération la mémoire MRAM (pour magnetoresistive random access memory, la mémoire non volatile de type magnétique).
4 Weil Hersteller versuchen, immer mehr Leistung aus Elektronikgeräten herauszuholen, sind alternative Speichermedien mehr und mehr gefragt. Paul Stevens hat sich mit dem Magnetoresistive Random Access Memory (MRAM) und einigen Varianten dieser Technologie beschäftigt.
Magnetoresistive random access memory is an attractive alternative
T
en years ago a 32MB Compactflash memory card would have been considered adequate for a digital camera, but today a digital camera with limited camcorder capability
could benefit from one of the many relatively low- cost memory cards with a capacity of 32GB. This requirement for a 1000-fold increase in memory capacity is not atypical; in other applications, from computers to industrial controllers, designers are demanding memory that is both of a higher capacity and faster. One of the alternatives to conventional non-
volatile memory is magnetoresistive random access memory (MRAM), in which data is stored by means of magnetic storage elements instead of as electric charges or current flows. A variation of MRAM is spin-transfer torque RAM (STT-RAM), which relies on spin-aligned electrons. While the different variations of MRAM technology are, compared with conventional memory, still in the early days of commercialisation, proponents of MRAM believe this technology offers an attractive combination of faster operation, reduced power consumption and, unlike flash RAM that can degrade when it is written to repeatedly, the potential for an indefinitely long life without degradation. Furthermore, while static random- access memory (SRAM), dynamic random- access memory (DRAM), electrically erasable programmable read-only memory (EEPROM) and flash memory all have slightly different characteristics, it is thought that MRAM could potentially replace all of these diverse types. In June 2011, Crocus Technology, a developer
communications, high-performance network processing, and high-temperature automotive and industrial applications.
Logical development
Most magnetic memories are based on arrays of memory cells, each of which contains two magnetic layers. The first, often called the reference layer, is always magnetised in one direction, while the second, called the storage layer, is magnetised in either the same direction as the reference layer to store a ‘1’ or the opposite direction to store a ‘0’. However, Crocus’ MLU architecture can be configured with fixed magnetisation to implement a traditional logical NOR (not Or) function, with floating magnetisation to implement a logical NAND (not And) function, or with driven magnetisation to implement a logical XOR (eXclusive Or) function. In high-
density memory applications, the MLU architecture enables
NAND configurations
Fig. 1. e2v offers the EV2A16A MRAM chip with an operating temperature range of -5 to +125˚C for extended-reliability applications.
to be implemented in magnetic memory; this was previously possible only with flash memory technology. According to
of magnetic semiconductors, unveiled its Magnetic- Logic-Unit (MLU) architecture, which it described as a scalable evolution of its Thermally Assisted Switching (TAS) technology for advanced memory and logic. Claiming this to be a first for the industry, Crocus said its innovative MLU architecture had the potential to create new applications in high-density data storage, secure commerce and
Crocus, MLU NAND memory can be two to four times denser than conventional magnetic memory, with the added benefit of fully random access. Crocus also offers an MLU XOR, called Match-In-Place, which implements ultra-secure compare and encryption functions that are claimed to make smart cards, identity cards, SIM cards and near-field communications (NFC) devices tamper-proof. Match-In-Place also implements the search and compare functions required in network routing applications and high-performance computing, and can achieve up to 50 times the density of conventional complementary metal- oxide-semiconductor (CMOS) hardware search processors. In addition, MLU is capable of operating at temperatures of up to 200°C, making it suitable for use in automotive and industrial electronics.
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