Electronic Design

Combo Chip Targets All 12- And 5-V Disk-Drive Applications

The L7250 voice coil and spindle motor-drive combo is designed to allow a single device to be used across a broad range of disk-drive applications. Based on a flexible digital architecture, this chip operates on 12- or 5-V supplies.

This device includes all of the circuits required to control and drive the voice-call actuator and spindle motor. The configuration includes all of the necessary power FET devices as well as the company's proprietary "Smooth Drive" pseudosinusoidal digital-drive technique. This technique minimizes acoustic noise in the drive. Controlled through a three-wire serial bus running at up to 33 MHz, this device is controlled through registers loaded and read by the system processor. The chip is manufactured using the company's bipolar CMOS-DMOS (BCD) technology.

The power FETs in the voice-coil actuator section deliver up to 2 A of peak current with an on resistance of 0.9 Ω at 125°C. Circuits are included for spindle current limiting, startup position sensing, and spindle braking during power-down. Synchronous rectification during pulse-width modulation reduces power dissipation. A dedicated analog-to-digital converter (ADC) compensates for power-supply variations. A class AB output stage has a zero dead band and minimal crossover distortion.

Available in a surface-mount plastic TQFP64, the L7250 costs $3.80 in quantities of 100+.

STMicroelectronics Inc.
(781) 861-2650; www.st.com

TAGS: Components
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