Dynamic magnetic information storage or retrieval – General processing of a digital signal – Head amplifier circuit
Reexamination Certificate
2001-02-28
2003-11-18
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Head amplifier circuit
C360S045000, C360S050000
Reexamination Certificate
active
06650493
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of magnetic or magneto-optic data storage devices, and more particularly but not by way of limitation, to improving data transfer rate performance by writing data with a magnetic field to a magnetizable medium using a write driver circuit providing a write current comprising a field reversing pulse current in phased relationship with a field maintenance continuous current.
BACKGROUND OF THE INVENTION
Disc drives are used as primary data storage devices in modern computer systems and networks. A typical disc drive comprises one or more rigid magnetizable storage discs which are rotated by a spindle motor at a high speed. An array of read/write heads transfer data between tracks of the discs and a host computer. The heads are mounted to an actuator assembly which is positioned so as to place a particular head adjacent the desired track.
Each of the discs is coated with a magnetizable medium wherein the data is retained as a series of magnetic domains of selected orientation. The data are imparted to the data disc by a write element of the corresponding head. The data thus stored to the disc are subsequently detected by a read element of the head. Although a variety of head constructions have been utilized historically, magneto-resistive (MR) heads are typically used in present generation disc drives. An MR head writer uses a thin-film inductive coil arranged about a ferromagnetic core having a write gap. As write currents are passed through the coil, a magnetic write field (sometimes referred to as the “write bubble”) is established emanating magnetic flux lines from the core and fringing across the write gap. The flux lines extend into the magnetizable medium to establish magnetization vectors in selected directions, or polarities, along the track on the data disc. Magnetic flux transitions are established at boundaries between adjacent magnetization vectors of opposite polarities.
To write a computer file to disc, the disc drive receives the file from the host computer in the form of input data which are buffered by an interface circuit. A write channel encodes and serializes the data to generate a data input stream that can be represented as a square-wave type signal of various lengths between rising and falling signal transitions.
A write driver circuit uses the data input stream to generate a write current which is applied to the write head, creating the write bubble that writes the encoded data to the magnetizable medium of the selected disc. The write current both reverses the polarity of the write bubble, creating the magnetic flux transitions, and sustains a given polarity between successive magnetic flux transitions.
Conventional write drivers employ continuous write currents. Continuous current writing is well suited for the relatively steady-state conditions between successive magnetic flux transitions. It is relatively difficult, however, to impart the magnetic flux transitions with continuous current writing, particularly at higher data transfer rates. This is due to the transitory rise/fall characteristics (sometimes referred to as slew rate) associated with reversing the polarity of a continuous write current.
Some write drivers employ pulse write currents. Pulse current writing is well suited for imparting the magnetic flux transitions. By using the data input stream to trigger a series of very short duration, discrete pulse currents, flux transitions with a relatively better edge definition can be created. However, sustaining the write current with only a pulse write driver between successive magnetic flux transitions can be problematic, especially over relatively long bit cell lengths.
There exists a need for improvements in the art to enhance write driver performance at ever-increasing data transfer rates, so as to better draw on the benefits of both types of write drivers.
SUMMARY OF INVENTION
The present invention provides an apparatus and an associated method for improving data transfer rate performance by writing data with a magnetic field to a magnetizable medium using a write driver circuit providing a write current comprising a field reversing pulse current in phased relationship with a field maintenance continuous current.
In one aspect of the present invention a method is provided for magnetically recording data to a magnetizable medium as a sequence of magnetic flux transitions. The method comprises providing a write element responsive to a current for generating a write field magnetizing the magnetizable medium. The method further comprises moving the magnetizable medium relative to the write element. The method further comprises providing a write current adaptively responsive to a data stream input for activating the write element to magnetically orient a first area of the medium in a first direction, the write current comprising a pulse current in a phased relationship with a continuous current. The method further comprises reversing the write current in response to the data stream input to magnetically orient a second area of the medium in a second direction.
In reversing the write current, the method applies the reversed write current generally during a transition window such that a portion of the first area remains within the write field so that a portion of the first area is magnetically reoriented by the reversed write current, the remaining portion of the first area having retained the first magnetization and traversed beyond the write field comprising a magnetization vector of a desired data bit length. More particularly, the maximum time associated with the transition window disposes the second area contiguous with the first area with no unrecorded gap therebetween.
In another aspect of the present invention a disc drive storage device is provided adapted for receiving a data input stream from a host computer and writing the data to storage. The disc drive storage device comprises a rotatable disc having a magnetizable medium storing the data as sequential magnetization vectors in alternating magnetic orientation. The disc drive storage device further comprises a write element operably adjacent the disc generating a write field for selectively magnetizing the magnetizable medium. The disc drive storage device further comprises a write driver circuit adaptively responsive to the data input stream and imparting a write current to the write element to magnetically orient the magnetizable medium in writing the data input stream to the disc, the write driver circuit comprising: a first source responsive to the data input stream for imparting a continuous current to the write element; a second source responsive to the data input stream for imparting a pulse current to the write element; and a delay timer phasing the responses of the first and second sources.
The disc drive storage device write driver imparts a write current to magnetically orient a first area of the magnetizable medium in a first direction, and imparts a reversed write current to magnetically orient a second area of the magnetizable medium in a second direction, the reversed write current being imparted during the transition window.
These and other features and benefits will become apparent upon a review of the following figures and their accompanying detailed description.
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Cesari Kirk A.
Figueroa Natalia
Seagate Technology LLC
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