SAN MATEO, Calif. -- Samsung Electronics said it has started offering NAND flash memory, used mostly as data storage memory in flash cards, as an alternative to NOR flash devices in multichip packages aimed at cell phone makers.
Though it may not have the random access performance of NOR-type codeflash devices, NAND may provide cell phone makers with a way to get to
higher densities at a lower cost.
"There was a worry about shortages of high-density NOR in the summer,
and some felt they should have a fallback position," said Alan Niebel of
Web-Feet Research Inc. in Monterey, Calif. "If it functions according to
speed, it may be a low-cost alternative. NAND tends to be cheaper than
NOR overall in the marketplace, though that doesn't mean the silicon-manufacturing costs are cheaper."
More density, less cost
As the latest Internet-browsing phones and forthcoming third-generation (3G) phones pack in more volatile and nonvolatile memory to keep up with new services, cell phone makers are looking to boost memory density while keeping costs and power consumption to a minimum.
"The higher-density flash is needed," Niebel said. "It's not only for protocol setups but also for messaging, voice answering, GPS global positioning satellite, storing different fonts and Web access."
As one of only a handful of NAND-type flash memory suppliers, Samsung may find even the small slice of the market it gets to be a lucrative slice. The company believes the wireless handset market will reach 420 million units in 2000 and will continue to grow 30% a year. Samsung expects the market for 3G handsets to hit 50 million units by 2003.
Samsung said it has already shipped its first engineering samples of stacked multichip modules with 8 Mbits of SRAM and a 64-Mbit NAND device.
The devices come packaged in an 8-by-13-by-1.2-mm ball-grid array with 69 signals. The NAND and SRAM share I/O and control pins, and the pin-out will accommodate SRAM as dense as 64 Mbits and NAND-type flash chips with 512 Mbytes of storage capacity, according to Samsung.
The MCP is set to operate between 2.4 and 3 volts. Designed with 0.18-micron geometry rules, 8-Mbit SRAM has an access time of 85 nanoseconds.
The NAND access speed will likely be slower than NOR flash, though slower flash speeds may not be a problem with "middle of the road" applications, Niebel said.
"The main problem with NAND is the initial read. You're getting up to 50 microseconds for the initial read, then 50 nanoseconds for subsequent reads," he said. "NOR's initial read can be as low as 70 nanoseconds and up to 150 nanoseconds, and then the subsequent reads in burst or
page mode can go down to the twenties or teens with some of them."
Samsung is planning to extend its NAND offering for cellular phones even further. Sometime in the first quarter of 2001, the company will introduce an MCP with 32 Mbits of what it calls unit transistor RAM and 64 Mbits of NAND flash.