Power Electronics

Hard-Disk Motor Controller Maximizes Battery Life

STMicroelectronics’ compact and highly-integrated hard disk-drive (HDD) Motor Controller targets 1.8-in. and sub-1.8-in. drives used in portable products such as MP3 and video players. The L7208 HDD Motor Controller integrates all of the circuits needed to control and drive the HDD spindle motor and voice coil actuator – including all the necessary power-FET devices – and is designed to save space and to minimize the drive’s power consumption. The IC includes two technologies: ST’s Smooth Drive pseudo-sinusoidal digital-drive technique for minimizing acoustic noise from the spindle motor and a free-fall sensor interface.

Power consumption is extremely low in all operating modes, including a highly efficient sleep mode. The class AB output stage has zero dead-band and minimal crossover distortion, and the power FETs can deliver up to 0.5 Apk. The voice-coil section includes a 14-bit D-A converter for current commands and load/unload circuits.

In addition to the Smooth Drive feature, the spindle-motor section includes circuits for spindle-current limiting, start-up position sensing, and spindle braking during power down. The L7208 is register controlled, and connects to the host system through a serial bus running at up to 50 MHz.

The HDD motor-controller family also includes the L7207, which is firmware compatible with the L7208 and is designed both for the 5-V drives made for mobile applications such as laptop computers, and for 12-V desktop computer drives. Available in an ultra-thin LGA package, the L7208 is priced at $15.00 each.

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