Wireless Systems Design

Flash-Density Doubling Leads To More Handset Memory

Mobile handsets are evolving rapidly. Much of this evolution is dependent upon memory advances. For example, look to Spansion (www.spansion.com), the Flash-memory subsidiary of AMD and Fujitsu Ltd. It expects Flash-memory requirements for mainstream phones to jump from about 150 Mb per phone in 2004 to over 500 Mb in 2007. High-end phones require even more Flash memory. They'll rise from about 750 Mb today to an estimated 5 Gb and beyond in 2007.

In keeping with this outlook, Spansion has unveiled plans for a new family of Flash-memory devices. This family will be part of its strategic MirrorBit technology initiative. The forthcoming RS family will simplify mobile-phone design with a single Flash-memory platform. Because it is based on the density-doubling MirrorBit technology, the RS family of devices is designed to offer the reliability and read performance that's expected from NOR-type products. Yet its die sizes will rival those of alternative NAND-type products. The initial 1.8-V, 512-Mb product is planned for early this year.

With Spansion's data-storage platform, cell-phone manufacturers will be able to design complete MirrorBit-technology-based memory subsystems for both code and data storage. They'll design those subsystems at densities that range from the low 16 Mb, which is on the market now, to as high as 5 Gb.

This single-platform concept will allow handset manufacturers to incorporate advanced multimedia capabilities, such as photos, video, and music, in the same handset platform that provides simple voice and SMS text-messaging services. In addition, mobile-phone makers should be able to lower their overall development costs while achieving faster time to market for new products. They also will be able to better allocate engineering resources to produce a wide range of phone designs. By pairing multiple densities of code-optimized Flash memory with high-density, data-optimized storage memory, the RS family will represent a broad selection of Flash densities. Each one will be suited for specific phone models and feature sets.

Essentially, the MirrorBit technology is a comparatively simple approach to storing two bits of data in a single Flash-memory cell. The technology is designed to be versatile enough to scale to a full range of densities. From 1-Mb serial-Flash products, it will scale to the highest-density NOR device that's currently on the market at 512 Mb. By 2007, it vows to scale to a planned 8 Gb using QuadBit technology. In addition, the technology will allow the company to easily integrate logic functions with very high densities of Flash. It also plans to extend performance to higher burst-write speeds.

To support a wide variety of mobile-phone designs while minimizing circuit-board-space requirements, Spansion will introduce its data storage devices in stacked multi-chip products (MCPs). It plans to sample multiple MCP configurations, which will feature up to 1.25 Gb of Flash memory, during this quarter.

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