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Hard-disk-drive motor controller from ST Microelectronics

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ST Microelectronics , provider of disk drive and system-on-chip solutions, unveiled a hard-disk drive (HDD) 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 Microelectronics provides HDD controllers, with a level of integration, enabling drive manufacturers to significantly reduce their bill of materials (BOM) and save space within the drive. ST Microelectronics offers server and workstation hard disk drives to benefit from smaller controller footprint, multiple efficient switching regulators, and lower acoustic noise

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. The new controller also eliminates 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 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.

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