New HDD Motor Controller Chip From STMicroelectronics

STMicroelectronics
announced a hard-disk drive motor-control chip intended for
demanding enterprise- level HDD applications. The new L7220 controller
integrates all of the circuits required to drive both the spindle motor
and the voice-coil motor (VCM), plus the motor drive power FETs and
multiple high-efficiency voltage regulators. It continues and
complements ST’s HDD controller family, which includes the L7207 HDD
controller for mobile and desktop drives.

ST is the market
leader in enterprise HDD controllers. No other manufacturer offers such
a high level of integration, enabling drive manufacturers to
significantly reduce their bill of materials (BOM) and save space
within the drive. Enterprise HDDs – typically used in server farms,
workstations and high-performance desktop systems – are moving to Small
Form Factor (SFF) sizes, where achieving a smaller PCB footprint is
critical; the integration in the L7220 of the power FETs for both
spindle and voice coil motors is a major contribution.

The new
controller embeds four highly-efficient hysteretic positive switching
regulators, and one -5V regulator, all with voltage margining. As well
as eliminating the need for external regulators for the various
voltages required by the drive, hysteretic control provides fast
transient response and very high efficiency, increasingly important in
server farms in particular, where reducing power consumption is a
principal requirement.

In addition, the L7220 contains the
latest version of ST’s respected Smooth Drive pseudo-sinusoidal
digital-drive technique for minimizing acoustic noise from the spindle
motor, plus other circuits to limit spindle current, sense the start-up
position and slow the spindle during power down.

The
spindle-motor section power FETs are capable of delivering 3.0A peak
current; ON-resistance is 0.3-ohms maximum at 125 degrees C. The VCM
driver has 2.5A capability and 0.3-ohms maximum bridge impedance. It
includes circuitry for discontinuous mode ramp unload at power off,
with end of travel detection; an alternative voltage-mode power-off
scheme; and a 15-bit linear DAC with gain switch, for current commands.

Evaluation
samples of the L7220 are available now, and volume production in
planned for mid-2008. The controller is priced at $15.00, in a 64-pin
10 x 10 x 1mm ePad package.

STMicroelectronics