Datasheet

MICRO DRIVES: TECHNOLOGY GOES TINY
Figure 3 is a picture of a micro hard drive. The aerodynamic electromagnetic head lies at
the end of a lightweight access arm that can position the head anywhere on the hard disc
platter in thousands of a second. Instead of multiple 2-foot (0.6-meter) platters, the micro
hard drive discs measure a mere 0.85, 1, or 1.8 inches (38.8, 45.7, or 25.4 mm) in
diameter. The disc spins at speeds of 3,200 to 4,200 rpm; and in some large-capacity
versions of these tiny drives, there are two discs in each drive. A very thin coating of
cobalt/chromium/platinum alloy deposited on the platter gives the disc its magnetic
properties. The design of the micro drives is nearly identical to that of standard hard
drives used in all computers today except that all the parts are smaller and the speeds are
somewhat slower. These drives lack the IDE or SATA cable connectors of their larger
brothers because they are often designed to transfer data through other interfaces such
as Compact Flash or USB connections. In many cases, the drives are permanently
embedded in a device and as in the Apple iPods. Figure 3 is an example of such an
embedded drive with its ribbon cable connector.
Access arm
Hard disc platter
Flying head
Figure 3
Although the design of micro hard drives is amazingly miniaturized, the concept of
magnetic recording in the laser age seems rather crude. Laser light does not wear out the
medium any more than flying heads would, and lasers are so much more “high-tech” than
modifications to devices dating from the 1950s. The laws of physics, however, are
immune to fashion. The fact is that thousands of magnetic particles laid end to end can fit
in a wavelength of light—even blue laser light. That means there is much greater storage
density potential in magnetic materials than in optical discs.
One problem has been that when these tiny particles, each of which is a single magnetic
domain, lie end to end, there is some cancellation of magnetic flux (energy) where positive
poles lie directly next to negative poles. That cancellation can lead to self-erasure when
the magnetic material cannot sustain the smallest magnetic patterns that a record head is
capable of producing.
4