M-Systems Flash Disk Pioneers Flash Memory Power Consumption, Summary, Parallel Multiplane Access

Implementing MLC NAND Flash for Cost-Effective, High-Capacity Memory

Parallel Multiplane Access

As discussed earlier, the MLC flash media is built of two planes that can operate in parallel. This architecture is one of the most powerful, x2 technology innovations, doubling read, write and erase performance. Two pages on different planes can be concurrently read or written if they have the same offset within their respective blocks, even if the blocks are unaligned.

Power Consumption

M-Systems’ Mobile DiskOnChip was designed for mobile systems that require very low power consumption. Therefore, the design incorporates power management features, such as Deep Power- Down mode, which consumes only 10 ∝A. Since the design is completely static (requiring no free- running clocks), it automatically goes into standby mode when not accessed. In addition, TrueFFS places Mobile DiskOnChip in Deep Power-Down mode at the end of every sector transfer. This design provides for a quick transition from Deep Power-Down mode to operational mode with minimal latency to minimize performance penalties.

Because x2 technology is seamlessly integrated into the existing DiskOnChip technology, power consumption levels for Mobile DiskOnChip G3 are equally as low. This is true despite the additional benefits of MLC and x2 technology.

Summary

The major improvements in flash NAND devices brought about by MLC technology are: much smaller size per bit, and consequently, a greatly reduced silicon size. These advantages come with added complexity in both device hardware architecture and device driver software. However, this document shows that x2 technology, by cleverly customizing the thin controller, TrueFFS and the flash media, provides a flash disk storage device based on MLC NAND that is as reliable and as fast as Binary flash devices in common use today.

Mobile DiskOnChip G3 512Mbit is M-Systems’ first product to implement MLC NAND and x2 technology. This product meets OEM storage requirements for highly reliable, high performance, high-capacity data storage in 2.5G and 3G mobile devices, using a greatly reduced silicon size in a the industry’s smallest BGA package, 7x10mm. Mobile DiskOnChip G3 is the most cost-effective memory solution available (Table 2). Future products that will use MLC NAND and x2 technology include Mobile DiskOnChip G3 in 256Mbit (32MByte) and 1Gbit (128MByte) capacities, as well as M-Systems’ highly successful DiskOnKey keychain storage device.

Table 2: Comparing NAND Flash Alternatives

		Binary NAND	MLC NAND	DiskOnChip G3 MLC
				NAND and x2
	Size	100%	~50% of Binary NAND	~53% of Binary NAND
	Sustained write	~800KB/sec	~350KB/sec	~700KB/sec
	performance
	Reliability	Occasional random	Frequent random errors	Perfect device
		errors
91-SR-014-02-8L				13