Abstract: A disk drive is disclosed comprising control circuitry for self servo writing a disk. An estimated reader/writer offset is initialized, servo bursts in a first servo track are read, the head is moved radially using the estimated reader/writer offset, and propagated servo bursts are written to a target servo track. The propagated servo bursts are read from the target servo track to generate a read signal, the read signal is processed to generate a burst crossing signal (BCS), and the estimated reader/writer offset is adjusted in response to the BCS.

Abstract: A disk drive is disclosed including a disk having a plurality of tracks, and a head actuated over the disk. A write frequency of write data received from a host is monitored. When the write frequency falls below a threshold, the disk drive is configured to operate in a low frequency access mode when accessing the disk, wherein a parameter of the disk drive is configured to increase the reliability of the disk drive. When the write frequency rises above a threshold, the disk drive is configured to operate in a high frequency access mode when accessing the disk, wherein the parameter of the disk drive is configured to increase the performance of the disk drive.

Abstract: A disk drive is disclosed including 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 spindle motor for rotating the disk, and a head actuated radially over the disk, wherein the head comprises a dynamic fly height (DFH) heater. Control circuitry within the disk drive is operable to select an operating control setting for the DFH heater by positioning the head over one of the tracks, measuring a first rotation time of the disk in response to at least one of the servo sectors, adjusting the control setting for the DFH heater, measuring a second rotation time of the disk in response to at least one of the servo sectors, and detecting whether the head has contacted the disk in response to the first and second rotation times.

Abstract: A disk drive is disclosed including a disk having a plurality of tracks, wherein each track comprises a plurality of servo sectors. The disk drive further comprises a head having a read element offset from a write element by a reader/writer offset. The read element is positioned over a first track and the write element is positioned over a second track. A first servo control signal is generated for servoing the head in response to the servo sectors in the first track, and first wedge repeatable runout (RRO) data is written to the second track along a substantially sinusoidal path corresponding to the reader/writer offset, wherein the first wedge RRO data are for writing data to a third track.

Abstract: A disk drive is disclosed comprising a plurality of servo sectors that define a plurality of tracks, and a head comprising a read element radially offset from a write element. The read element is positioned over a first track, and the first track is read to generate first read wedge repeatable runout (WRRO) values. A first seek operation of the head positions the read element over a second track, and the second track is read to generate first write WRRO values. The first write WRRO values are used to write the first read WRRO values to the first track. A second seek operation of the head positions the read element over a third track, and the third track is read to generate second write WRRO values. The second write WRRO values are used to write the first write WRRO values to the second track.

Abstract: A disk drive is disclosed including a disk having a plurality of tracks, wherein each track comprises a plurality of embedded servo sectors. A head connected to a distal end of an actuator arm is rotated about a pivot by a voice coil motor (VCM) in order to actuate the head radially over the disk. The actuator arm is unloaded onto a ramp by seeking the head to a track near an outer diameter of the disk in response to the embedded servo sectors, switching to a velocity control mode to unload the actuator arm onto the ramp at a controlled unload velocity in response to a back electromotive force voltage generated by the VCM, and ramping a velocity command so that the velocity of the actuator arm when contacting the ramp is less than half the maximum unload velocity while traveling along the ramp.

Abstract: A disk drive is disclosed comprising a head actuated over a disk. A redundancy generator generates a plurality of redundancy symbols appended to user data to form a codeword C(x) written to a selected data sector on the disk. During a read operation, a syndrome generator generates a plurality of error syndromes in response to a received codeword C?(x) generated by reading the selected data sector. An error detector, responsive to the error syndromes, detects a number of errors in the received codeword C?(x), and a plurality of counters count a number of times the number of errors falls within a predetermined plurality of ranges to thereby provide a distribution of the errors. The error distribution is used, for example, for selecting a track density or ECC depth, or for failure prediction or defect mapping.

Abstract: A disk drive is disclosed including a disk, a spindle motor operable to rotate the disk, a head, and a voice coil motor (VCM) operable to actuate the head over the disk, wherein the VCM comprises a voice coil. The disk drive further comprises a capacitor, and a back electromotive force (BEMF) voltage generator operable to generate a BEMF voltage from the spindle motor. The disk drive further comprises switching circuitry operable to connect the voice coil to the capacitor while accelerating the VCM, and to disconnect the voice coil from the capacitor and connect the voice coil to the BEMF voltage while decelerating the VCM.

Abstract: A disk drive is disclosed including a disk having a plurality of data tracks, wherein each data track includes a plurality of data sectors. A head is actuated over the disk for accessing the data sectors. A write command is received from a host, wherein the write command includes a host block and corresponding host block address. The host block is partitioned into a plurality of sub blocks, and a plurality of sub block addresses are generated in response to the host block address, wherein each sub block address corresponds to one of the sub blocks. Error detection code (EDC) data is generated for each sub block in response to the sub block and corresponding sub block address. Each sub block and corresponding EDC data are combined to generate a plurality of partial codewords that are written to the data sectors corresponding to the sub block addresses.

Abstract: 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.

Abstract: A method of writing spiral tracks for a disk drive is disclosed. A first concentric reference track is written at a first radial location near an outer diameter of a disk surface, a second concentric reference track is written at a second radial location near an inner diameter of the disk surface, and a third concentric reference track is written at a third radial location between the first and second radial locations. Prior to writing one of the spiral tracks, the concentric reference tracks are read to generate position error signals used to adjust a velocity profile for writing the spiral tracks. The velocity profile is adjusted to compensate for linear and non-linear disturbances due, for example, to thermal expansion.

Abstract: 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.

Abstract: A method is disclosed for writing M spiral tracks (i=1 to M) to a disk of a disk drive. A head is positioned over a first radial location to write a concentric reference track comprising N concentric servo sectors. Prior to writing one of the spiral tracks, the concentric reference track is read and a position error signal first_PESi(j) is generated for at least one of the servo sectors j in the concentric reference track, wherein the first_PESi(j) represents an offset of the head from the first radial location, and the servo sector j corresponds to a circumferential location of the spiral track. At least one of a starting radial location and a velocity profile is adjusted in response to the first_PESi(j), and the spiral track is written to the disk using the starting radial location and the velocity profile.

Abstract: A method is disclosed for writing product servo sectors to the disk of a disk drive by demodulating spiral tracks recorded on the disk. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The high frequency signal is demodulated into a plurality of servo burst signals, and a position error signal is generated from the servo burst signals. A correlation between the position error signal and an off-track displacement of a head is calibrated, for example, by moving the head radially over the disk until the servo burst signals attain a first predetermined relationship, and then calibrating the correlation in response to the corresponding position error signal.

Abstract: A disk drive is disclosed including a disk, an actuator arm, a head attached to a distal end of the actuator arm, a mechanical position sensor operable to generate a position signal representing a position of the head relative to the disk, and a voice coil motor for rotating the actuator arm about a pivot. The disk is rotated at a predetermined velocity, a control signal is generated in response to the position signal generated by the mechanical position sensor, and the control signal is applied to the voice coil motor in order to seek the head radially over the disk while writing a spiral track to the disk. The spiral track is then processed to maintain the head along a servo track while writing product servo sectors along the servo track.

Abstract: A method of servo writing a plurality of servo sectors to a disk of a disk drive to define a plurality of data tracks is disclosed. The disk drive comprises the disk, an actuator arm, a head coupled to a distal end of the actuator arm, wherein the head comprises a read element and a write element. A voice coil motor (VCM) rotates the actuator arm about a pivot to actuate the head radially over the disk, and a secondary actuator adjusts a skew angle for the head while using the write element to write the servo sectors to the disk.

Abstract: A switching voltage regulator is disclosed for regulating a voltage supplied to system circuitry. The switching voltage regulator comprises an oscillator operable to generate an oscillator signal representing a gate speed of a reference circuit in the system circuitry, and a frequency generator operable to generate a reference signal representing a target gate speed of the reference circuit. A cycle comparator compares at least one cycle of the oscillator signal to at least one cycle of the reference signal, and switching circuitry charges a charging element based at least on part on the comparison.

Abstract: A disk drive is disclosed including a disk having a plurality of servo tracks. The servo tracks are banded together to form a plurality of servo track bands, and each servo sector comprises a fine track address that identifies one of the servo tracks. The disk drive further comprises a head attached to a distal end of an actuator arm operable to generate a read signal by reading the disk, and a mechanical position sensor operable to detect a coarse position of the actuator arm. The coarse position is processed to identify one of the servo track bands, and the read signal is processed to detect one of the fine track addresses, wherein the detected fine track address identifies a servo track within the identified servo track band. The identified servo track band is combined with the detected fine track address to generate a servo track address.

Abstract: A disk drive is disclosed employing a VCM control loop comprising a voltage detector operable to detect a back EMF voltage across a voice coil of a voice coil motor, a current detector operable to detect a current flowing through the voice coil, and a control voltage generator, responsive to a command input and the detected back EMF voltage, operable to generate a control voltage applied to the voice coil. Control circuitry within the disk drive (a) initializes the control voltage; (b) injects a transient into the VCM control loop and detects a corresponding current flowing through the voice coil; (c) adjusts the control voltage in response to a polarity of the detected current; (d) repeats elements (b) and (c) at least once; and (e) stores an offset value in response to the adjusted control voltage.

Abstract: A disk drive is disclosed which receives a plurality of access commands from a host, where each access command identifies a target track. The access commands are stored in a command queue, and for each command in the command queue, a seek length is computed corresponding to a number of tracks between a current track the head is over and the target track of the access command. A seek time is computed in response to the seek length using a seek profile comprising a first plurality of seek length segments and a variance group comprising a second plurality of seek length segments. Each seek length segment corresponds to a range of seek lengths, and the first plurality of seek length segments is different than the second plurality of seek length segments.