Winbond stacks NOR and NAND dies in 8-pin memory package
The SpiStack W25M Series allows the “stacking” of homogeneous or heterogeneous flash, thus achieving memories of varying densities for code and/or data storage, while providing designers with the flash solutions most appropriate for their design requirements in the well-established 8-pin package. Additionally, W25M memories feature the popular, multi-IO SpiFlash interface and command set. SpiStack homogeneous memories are achieved by stacking SpiFlash dies – for example, two 256Mb dies combining to form a single SpiFlash 512Mb NOR memory – in the industry-standard 8-pin 8x6mm WSON package.
This stacked product, W25M512JV, is also available in the widely used 16-pin SOIC or 24-pad BGA packages and is sampling now. SpiStack heterogeneous memories call for the stacking of a NOR memory with a NAND die, such as a 64Mb SpiFlash NOR blended with a 1Gb Serial NAND die, which gives designers the flexibility to store code in the NOR die and data in the NAND memory. Winbond will offer multiple SpiFlash configurations, each with density ranging from 16Mb to 2Gb, to be stacked with any combination of NOR and NAND dies.
Each die can be used according to its specifically beneficial characteristics. A NOR die can be used to store the boot code, thanks to its cell characteristics that deliver better endurance and retention, and fast random access time. A NAND memory can be used to store data and/or to back up the boot code.
A NAND die can also be used to upload the working memory data quickly whenever the system power goes down, thanks to its programming time that’s much faster than NOR. It improves the system quality by storing up-to-date code residing in the working memory for later usage.
SpiStack supports concurrent operation so that code execution is not interrupted for data updates. All SpiStack features are supported in an 8-pin package along with the standard QSPI command, so that backward compatibility is conserved. This is done with the addition of a simple software die select instruction (C2h) and a factory-assigned die ID number. The dies are stacked based on Winbond’s unique stacking process technology.
Winbond SpiFlash memories are manufactured in the company’s 12-inch wafer fabrication facility in Taichung, Taiwan.
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