Highly integrated hard-disk-drive motor controller designed for next-generation enterprise drives
(Product News, 30 Jan 2008 )
STMicroelectronics has launched 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.
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.
