Testing mobile memories: it's a phone. No, it's a camera ... a computer ... a TV. Whatever you call it, it's a huge test challenge for memory manufacturers.(MEMORY TEST)(Cover Story)

As we expect our mobile phones to play MP3s, take still pictures, provide PDA functionality, and stream video, the required amount and types of memory increase. This convergence in the mobile communications market combined with ever-shrinking form factors drives manufacturers to consider different packaging solutions for mobile memories.

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One solution is to package the various types of memory required for these devices in a single multichip package (MCP). This helps manufacturers offer new multifunction devices without increasing the overall size of the end product. With the enhanced functionality that the MCPs enable come new test challenges for memory manufacturers.

Divergent Requirements

In 1990, I was sure to impress those around me whenever I pulled out my mobile phone. Immediately everybody knew that I was too important to ever be out of touch.

Now the world has changed. My stepfather uses his mobile phone to watch the Kings basketball team while he takes his grandson for a walk. Going outside no longer stops my nephew from playing his games. And my boss never is really in a meeting but rather in two or three since he always is either TXTing or e-mailing somebody with his phone.

With mobile phones, one thing is certain: They are no longer just for talking. As they become our means of staying connected to each other and the Internet, trade-offs must be made among functionality, battery life, price, and size.

Many of these trade-offs relate directly to the types of memory chosen for the phone. My first mobile phone had a small amount of NOR flash, maybe 8 Mb, for storing the program that ran the phone. It also had an even smaller amount of low-power SRAM, maybe 1 Mb, that served as working memory because the program time of flash is too long.

This combination worked well, and the natural bit growth of the NOR and SRAM met the growing requirements for phones until the inclusion of large color screens, high pixel-count cameras, and MP3 player capability drove the need for the ultra-high densities of NAND flash. Now the applications processors that allow phones to perform as PDAs, portable game players, and televisions require NAND flash to store the complex programs and mobile SDRAM performance to provide the user with the best possible experience. …

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