M-Systems Flash Disk Pioneers Flash Memory - Manual (Page 13)

Implementing MLC NAND Flash for Cost-Effective, High-Capacity Memory
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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
µA. 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
performance
~800KB/sec ~350KB/sec ~700KB/sec
Reliability Occasional random
errors
Frequent random errors Perfect device