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New technology doubles storage capacity in NOR flash devices

Posted: 27 Jun 2005 ?? ?Print Version ?Bookmark and Share

Keywords:stb? pda? nor flash? macronix? nbit?

Offers twice the density in the same die sizeDesigners of STBs, PDAs, or any other system that requires high-density NOR flash can get twice the memory density in the same die size vs. conventional technologies with Macronix's latest family of devices that employ the company's newest technology called NBit.

NBit is a nitride-based multiple bits/cell technology that stores two bits of information per cell. With alternative technologies, like multi-level cell (mlc), four cell levels are needed to store two bits of information.

By equipping its latest devices with NBit, Macronix can offer designers twice the density in the same die size, said K.C. Shekar, director of strategic marketing at Macronix.

For example, storing 32Mb of information using NBit technology consumes approximately the same die area as a flash device based on the older 1-bit/cell technology that stores 16Mb.

"The technology is simple, and reliable and the cell is very compact," Shekar said. "In comparison to the single bit/cell products, these NBit, 2bits/cell products also offer a page read/write function, which provides faster system operation."

To physically store 2-bits of information in a cell, two levels, '1' and '0', are required and can be done in two different locations on the cell. Unlike technologies based on floating gate cells, the nature of nitride technology is such that the charge that is stored on one side of the cell does not drift over the other side of the cell; therefore, the two locations on the same cell are physically distinct.

"In the case of MLC technology, the way they do it is they store '00' '01' '10' '11' so they need four different voltage levels to be detected within each cell to store two bits of information. To store three bits, they need eight levels, and to store 4 bits they need 16 levels. The complexity becomes significant."

One of the key features of NBit flash is its compatibility to Spansion MirrorBit compatible flash products. They are pin compatible, command compatible and socket replaceable, Shekar said. "We are the only second source to those products in the industry."

Programming of each bit is performed by hot electron injection, erase is performed by band-to-band tunneling and read by the reverse and read mechanism. NBit is also more scalable than competitive technologies.

"NBit is the technology of the future for the company, and we are offering our high density flash and ROM products starting with 32Mb going to 1Gb and beyond," said Dr. C.Y. Lu, senior vice president and CTO of Macronix.

The products
The 32Mb and 64Mb NOR flash devices are available in production quantities today, Shekar said. A 128Mb device is sampling now and will be in production within a month, he added.

The parts operate over a voltage range of 2.7V to 3.6V and are available in Boot and Uniform Sector architectures with x8, x16 and x8/x16 selectable configurations.

The family also supports advanced page mode operation for read and program functions to enhance system efficiency. NBit Flash offers 20-year data retention and a minimum of 100,000-cycle endurance over the life of the device. Each device complies with JEDEC industry standard software commands, pin-outs and package types.

The devices are offered in 48-, and 56-TSOP and 48- and 64-ball CSP, using Pb-free technology for RoHS-compliance.

Since the latest devices implementing NBit can store twice the density of those using 1-bit/cell technology, they are naturally much cheaper. Macronix's latest 64Mb device in 10,000-unit quantities costs $3.25 compared with the single-bit per cell technology version, which costs $4. "It's significantly cheaper," Shekar said.

The 64Mb device is also more powerful. Operating at 2.7V to 3.6V, the device provides a random access time of 90ns and page-access time of 25ns. At 3V to 3.6V, it can achieve a random access time as fast as 70ns. All of the NBit flash products are compatible to Spansion's equivalent MirrorBit flash devices.

"As Macronix develops the NBit family of NROM-based products, the storage side of the non-volatile market opens them up," said Alan Niebel, principal analyst at Web-Feet Research. "This expansion into the storage market validates the NROM-type flash offered through Spansion, Infineon and Saifun, and positions Macronix as a world-class memory manufacturer."

- Ismini Scouras

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