STMicroelectronics Introduces the L7250 Voice-Coil and Spindle-Motor Drive Combo Chip
STMicroelectronics (ST, Lexington, MA) has introduced a voice-coil and spindle motor-drive combination chip for all 12V and 5V disk-drive applications. Designed to allow a single device to be used across a broad range of disk-drive applications, the new L7250 is based on a digital architecture.
The L7250 includes all of the circuits needed to control and drive the voice-coil actuator and spindle motor, including all the necessary power FET devices and ST's proprietary Smooth Drive pseudo-sinusoidal digital drive technique, which minimizes acoustic noise in the drive. Controlled through a three-wire serial bus running at up to 33MHz, the L7250 is controlled through registers loaded and read by the system processor. ST's bipolar CMOS-DMOS technology is used to manufacture the chip.
Capable of 2.5A peak current, the spindle-motor section includes all power FETs with a maximum on resistance of 0.9Ohms at 125 degrees C. Circuits are included for spindle current-limiting, start-up position-sensing and spindle braking during power-down. Synchronous rectification during pulse-width modulation reduces power dissipation, and a dedicated analog-to-digital converter compensates for power-supply variations.
The power FETs in the voice-coil actuator section deliver up to 2A peak current with an on resistance of 0.9Ohms at 125 degrees C. This Class AB output stage has a zero dead band and minimal crossover distortion. The voice-coil section includes a 15-bit digital-to-analog converter for current commands, a sense amplifier gain switch and ramp load/unload circuits, plus a constant voltage-retract function. Auxiliary functions integrated on the chip include an internal Isofet, 10-bit ADC, 3.3V and 1.8V linear regulators, a shock sensor circuit suitable for piezoelectric or charging elements, power monitors for all voltages, and a negative voltage regulator.
The L7250 uses a TQFP64 surface-mounting plastic package. Samples will be available in the fourth quarter of 2001, with production quantities expected in the first quarter of 2002. The L7250 will be priced at $3.80 for quantities of 100.
