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Spindle Motor Phase Fine Slew Rate Control for HDD

IP.com Disclosure Number: IPCOM000014042D
Original Publication Date: 2001-Nov-17
Included in the Prior Art Database: 2003-Jun-19
Document File: 3 page(s) / 66K

Publishing Venue

IBM

Abstract

In Hard Disk Drives, one or more disks are mounted on a spindle. The spindle is rotated by an electric motor. The friction force of a rotating spindle can vary depending on many factors. Some factors which affect this friction force are listed here. Head position (over the media or stowed away from the media). Rotational velocity. Number of disks. The slew rate which provides the optimum rotational velocity accuracy and acoustic characteristics may vary with different spindle rotational friction force coefficients.

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Spindle Motor Phase Fine Slew Rate Control for HDD

In Hard Disk Drives, one or more disks are mounted on a spindle. The spindle is rotated by an electric motor. The friction force of a rotating spindle can vary depending on many factors. Some factors which affect this friction force are listed here.

Head position (over the media or stowed away from the media). Rotational velocity.

Number of disks.

The slew rate which provides the optimum rotational velocity accuracy and acoustic characteristics may vary with different spindle rotational friction force coefficients.

This invention is a spindle motor control method which implements different slew rates for an HDD based on the head position, rotational velocity, and particular model. Optimal slew rates can be chosen separately for all combinations of these parameters.

A spindle driver is used which has a 10 bit register that specifies the slew rate. This allows precise tuning to achieve the optimal slew rate for each HDD model in each state. Testing and slew rate tuning is done for each HDD model (number of disks, and operational velocity) in each state (spinning-up, heads over media, and heads stowed).

In a design that uses only one slew rate value, a compromise may need to be made. A slew rate must be found which can (for all models) both achieve the correct velocity during spin-up and maintain that velocity during operation.

By using different slew rates based on head position, rotational velocity, and particular...