Western Digital Technologies, Inc.

Western Digital (fremont), Inc.

Jack M Chue

Jai N Subrahmanyam

Siri S Weerasooriya

Robert L Cloke

Tehri S Lee

David Price Turner

William C Tipton, Ii

Raffi Codilian

Mohamad Towfik Krounbi

Guoxiao Guo

Charles A Park

Robert J McNab

David D Nguyen

Kathy X Tang

William D Johns

John Cuda

Gary L Dunbar

Tomas D Hugunin

Loi Dac Pham

Gopalakrishna Kote

Kroum Stanimirov Stoev

Yugang Wang

Jie Yu

Tao Pan

Wei Guo

Michael A Chang

Darrell Dean Palmer

Carl E Barlow

Richard Koonwai Wong

Sanghoon Chu

William Don Huber

Vinay Kumar Agarwal

Wing Ying

Russ A Quisenberry

Daniel B Razum

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of servo tracks defined by full sectors and intervening short servo sectors, where each full servo sector comprises a preamble, a sync mark, and servo bursts, and each short servo sector comprises a reference pattern and servo bursts. A first phase error is generated based on the sync mark in a first full servo sector, and a disk locked clock is adjusted in response to the first phase error. A second phase error is generated based on the reference pattern in a first short servo sector, and the second phase error is processed to determine whether the disk locked clock slipped a cycle before the head reaching the first short servo sector.

Disk drive compensating for cycle slip of disk locked clock when reading mini-wedge

A disk drive is disclosed comprising a plurality of disk surfaces, and a plurality of heads actuated over the respective disk surfaces. In one embodiment, control circuitry generates a pulse duty cycle signal for one of the heads. In another embodiment, the control circuitry generates a first pulse width modulated signal for a first head, and a second pulse width modulated signal for a second head, wherein the second pulse width modulated signal comprises a phase offset from the first pulse width modulated signal.

Disk drive employing pulse width modulation of head control signal

A disk drive is disclosed comprising a disk including a plurality of servo tracks defined by a plurality of servo sectors, wherein each servo sector comprises a plurality of servo bursts, and each servo burst comprises at least one of four phases. A first two of the phases are orthogonal, and a second two of the phases are orthogonal. As a head is actuated over the disk a servo sector is read to generate a read signal. The read signal is processed to demodulate the servo bursts into a position error signal (PES) representing an offset of the head from a target radial location on the disk, and the read signal is also processed to decode at least two of the phases of the servo bursts into a binary sequence.

Disk drive decoding binary sequence from phases of servo bursts

A perpendicular recording head is provided having a bottom pole, a writer pole disposed above the bottom pole, and a top shield disposed above the writer pole. The bottom pole and the top shield are both magnetically coupled to the writer pole. The writer pole includes a concave facing surface that faces the top shield. The top shield can include a convex surface that faces the writer pole. The top shield can also include a pedestal that protrudes towards the writer pole.

Perpendicular recording head with shaped pole surfaces for higher linear data densities

A method of selecting a dynamic fly height (DFH) control setting for a head in a disk drive is disclosed. The head is servoed over a disk, and a fly height measurement is generated for the head. A frequency component is extracted from the fly height measurement, and the DFH control setting for the head is adjusted in response to the extracted frequency component.

Feed forward compensation for fly height control in a disk drive

A disk drive is disclosed comprising a disk including a plurality of servo tracks defined by a plurality of servo sectors, wherein each servo sector comprises a plurality of servo bursts. The disk drive further comprises a head actuated over the disk. A servo sector is read to generate a read signal which is processed to demodulate the servo bursts into a position error signal (PES) representing an offset of the head from a target radial location on the disk. The read signal is also processed to decode the servo bursts into a Gray codeword representing at least part of a servo track address, wherein the servo track address represents a servo track the head is over.

Disk drive comprising gray code implemented with servo bursts

A disk drive is disclosed comprising a disk having a plurality of tracks, wherein each track comprises a plurality of data sectors and a plurality of servo sectors. The disk drive further comprises a head actuated over the disk, the head comprising a read element radially offset from a write element by a reader/writer offset. In order to rewrite a marginal servo sector detected in a target track, control circuitry within the disk drive relocates user data recorded in a first data sector of a near adjacent track to a staging memory. Servo data is written over the first data sector, and the read element is used to read the servo data written over the first data sector to actuate the head to rewrite the marginal servo sector of the target track. The user data stored in the staging memory is then rewritten to the first data sector.

Disk drive rewriting servo sectors by writing and servoing off of temporary servo data written in data sectors

A disk drive is disclosed including a disk having a first and second set of time-based servo patterns. The first set of time-based servo patterns comprises a first cyclical pattern that repeats radially over the disk, and the second set of time-based servo patterns comprises a second cyclical pattern that repeats radially over the disk, wherein each cyclical pattern comprises a plurality of timing marks. One of the first cyclical patterns overlaps at least part of a first servo track, and one of the second cyclical patterns overlaps at least part of the first servo track. At least one of the first and second set of time-based servo patterns are demodulated by detecting first and second time intervals relative to the timing marks, and a control signal for actuating the head is generated in response to the first and second time intervals.

Disk drive demodulating a time-based servo pattern

A method and apparatus is disclosed for adjusting the track density by changing the slope of spiral tracks used to servo write a disk drive. A target track density is established for a disk surface, and a plurality of spiral tracks are written to the disk surface in response to the target track density. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark, and a slope of the spiral tracks is selected in response to the target track density. The head internal to the disk drive is used to read the spiral tracks in order to write product servo sectors to the disk to define a plurality of data tracks, wherein the slope of the spiral tracks determines the density of the data tracks.

Adjusting track density by changing slope of spiral tracks used to servo write a disk drive

A method of servo writing a disk for use in a disk drive is disclosed by writing discontinuous spiral tracks on the disk to protect against overheating the head and/or preamp circuitry. A write clock is synchronized to the rotation of the disk, and a plurality of discontinuous spiral tracks are written on the disk. Each discontinuous spiral track is written at a predetermined circular location determined from the write clock, and each discontinuous spiral track comprises a plurality of segments separated by gaps. Each segment comprises a high frequency signal interrupted at a predetermined interval by a sync mark.

Servo writing a disk drive by writing discontinuous spiral tracks to prevent overheating

A system and method for processing track identifier errors to mitigate head instability in data storage devices is disclosed. The system and method includes computing a track id differential between an expected track id and a received track id, encoding the expected track id and the received track id, initiating a first action if the track id differential exceeds a pre-determined threshold and the encoded expected track id varies from the encoded received track id by a pre-configured number of bits, and initiating a second action if the track id differential does not exceed the pre-determined threshold or the encoded expected track id does not vary from the encoded received track id by a pre-configured number of bits.

System and method for processing track identifier errors to mitigate head instability in data storage devices

A disk drive is disclosed comprising a disk, a head actuated over the disk, and a spindle motor for rotating the disk. The spindle motor comprises a rotating component, a stationary component, and a first and second bearing assembly disposed between the rotating component and stationary component for rotating the rotating component about the stationary component, wherein the disk is attached to the rotating component. The bearing assemblies comprise a stationary component surface and a rotating component surface having a lubricant disposed there between. The first bearing assembly employs an anionic lubricant such that a first voltage forms between the stationary component surface and the rotating component surface when the rotating component rotates about the stationary component. The second bearing assembly employs a cationic lubricant such that a second voltage forms between the stationary component surface and the rotating component surface when the rotating component rotates about the stationary component. A polarity of the second voltage being opposite a polarity of the first voltage to thereby reduce the potential at the disk surface.

Disk drive comprising a spindle motor employing anionic/cationic lubricant to reduce disk surface potential

A disk drive is disclosed comprising a disk having a plurality of servo sectors forming a plurality of substantially linear servo wedges extending from an outer diameter of the disk to an inner diameter of the disk, wherein each servo sector is written using perpendicular magnetic recording. The disk drive further comprises a head coupled to a distal end of an actuator arm that is rotated by a rotary actuator about a pivot in order to actuate the head radially over the disk in a substantially arcuate path.

Servo writing substantially linear servo wedges to reduce overwrite effect in perpendicular magnetic recording

A head stack assembly includes a flex cable assembly. The head stack assembly further includes an actuator arm and a load beam coupled to the actuator arm. The head stack assembly further includes a trace suspension assembly backing layer coupled to the load beam and including a gimbal. The head stack assembly further includes a dielectric layer disposed upon the trace suspension assembly backing layer. The head stack assembly further includes a slider supported by the gimbal. The head stack assembly further includes a ground trace disposed upon the dielectric layer with the dielectric layer between the ground trace and the trace suspension assembly backing layer. The ground trace extends along the actuator arm and is electrically connected to the slider and the flex cable assembly for grounding the slider to the flex cable assembly.

Head stack assembly including a trace suspension assembly backing layer and a ground trace for grounding a slider

The present invention may be embodied in a disk drive comprising a rotating magnetic media having tracks identified by binary codewords, and in a related method. Each track codeword for a particular track within a contiguous band of tracks differs from a track codeword for an adjacent track within the contiguous band of tracks by a defined number of bits, and differs from a track codeword for a nonadjacent track within the contiguous band of tracks by at least the defined number of bits. The defined number N of bits is greater than four such that at least two bit errors may be corrected when reading a track codeword.

Growing community of inventors

Los Altos, CA, United States of America

Jack M Chue