Agere Systems Inc.

Western Digital (Fremont), Inc.

Carl F Elliott

John D Leighton

Ross Wilson

Cameron Carroll Rabe

Michael John O'Brien

Scott M O'Brien

Robert Wimmer

Sally A Doherty

Nameeta Krenz

Zhigang Bai

Tao Pan

Hao Fang

Jason A Christianson

Jonathan P Comeau

Jeffrey M Wisted

John D Leigthon

Thomas K Adams

Daniel J Galaba

Systems and methods for providing stacked writer leads for magnetic transducers used in disk drives are provided. One such system for providing stacked writer leads for a magnetic transducer includes a writer coil for the magnetic transducer, a first pad on the magnetic transducer, a second pad on the magnetic transducer, a first circuit trace coupled to the first pad and a first terminal of the writer coil, and a second circuit trace coupled to the second pad and a second terminal of the writer coil, where a preselected length of the first circuit trace and the second circuit trace is configured in a stacked configuration where each of the preselected lengths of the first circuit trace and the second circuit trace is positioned at about the same location in spaced apart planes.

Systems and methods for providing stacked writer leads for magnetic transducers

An apparatus and method for providing electrostatic discharge protection for a disc drive read head. A pair of depletion mode MOSFETS, and a fuse associated with each are disposed between the read head output terminals. The MOSFETS are controlled to an 'off' state for testing the preamplifier prior to assembly of the read head. After assembly of the head, a second pair of MOSFETS is gated to an 'on' state to open the fuses and thus permit normal operation of the read head.

Method and apparatus for protecting magnetoresistive heads from electrostatic discharge

An apparatus and method for demagnetizing a write head of a disc drive. Under control of a clock oscillator, synthetic demagnetizing pulses are generated and applied to a writer-driver bridge. Also under control of the clock oscillator, a write current produced by the writer-driver bridge incorporates the demagnetizing pulses and ramps down to about zero. The train of demagnetizing pulses and the write current ramp down demagnetizes the head, reducing write head magnetic bias that may influence the proximate read head of the disc drive head.

Method and apparatus for write head demagnetization

A disc drive system, such as a magnetic or optical recording and/or playback system, for low-data rate applications implements one or more circuit operations, such as read signal detection and related servo functions, as software-based digital signal processing steps in a dedicated software-based processor. The drive system incorporates increased buffering, modified input sample processing techniques, multiplexing of processing functions, and modified automatic gain control techniques to allow circuit operations to be performed with software-based digital signal processing techniques.

Signal processing in a disc drive

A recording system stores recording cycle information identifying the parameters for recording user data on a particular data sector. During a subsequent operation, the recording system employs the recording cycle information to select a different set of parameters for recording new user data at the particular data sector. One of the parameters might identify a recorded pattern in a balance pad at the data sector, and another one of the parameters might identify a scrambler seed value. By employing a different set of recording parameters for each occurrence of recording user data at the particular sector, sample timing of, for example, a read channel might be based on an average of easy and hard transitions.

Over-writing data in a recording system

A write driver circuit selectively provides a write current through a write head in first and second opposite directions. The write driver circuit is connected to the write head through an interconnect. The write driver circuit provides an incident write current signal through the interconnect to the write head, and also provides a reflection cancellation signal through the interconnect to the write head. In an exemplary embodiment, the incident write current signal is provided by providing an incident voltage signal across the write head, and the reflection cancellation signal is provided by providing a reflection cancellation voltage signal across the write head. In an exemplary embodiment, the reflection cancellation signal is a delayed and filtered version of the incident write current signal that cancels a reflected signal that is reflected at the interface between the interconnect and the write head due to impedance mismatching.

Disk drive writer with active reflection cancellation

A write driver circuit selectively provides write current through a write head in first and second opposite directions. First and second active devices are driven with first and second pre-drive signals. Third and fourth active devices are driven with third and fourth pre-drive signals. First and second pull-up resistances are provided respectively between the first and second active devices and a fixed voltage, and third and fourth pull-up resistances are provided respectively between the third and fourth active devices and the fixed voltage. A first capacitor is connected between the first active device and an intermediate point of the third pull-up resistance, and a second capacitor is connected between the second active device and an intermediate point of the fourth pull-up resistance.

Disk drive writer with capacitive boost

A disk driver writer precompensation system modulates the write current waveform based on a pattern of data bits magnetically recorded on a medium in order to adjust the timing of magnetic transitions recorded on the medium.

Disk drive writer waveform induced precompensation

A preamplifier system is connected through an interconnect to a read head. The preamplifier system includes a voltage-sense preamplifier having at least one input connected through the interconnect to the read head and having at least one output, and also includes a current-sense preamplifier having at least one input connected through the interconnect to the read head and having at least one output. A summing circuit is connected to combine the outputs of the voltage-sense preamplifier and the current-sense preamplifier. For optimal performance, the preamplifier system is impedance matched to the interconnect. The preamplifier system achieves excellent response due to impedance matching with acceptably low noise levels, since the correlated noise associated with the current-sense preamplifier is canceled at the summing circuit.

Dual-sense impedance-matched reader

A plurality of data bits are magnetically recorded on a medium (such as a magnetic disk in a disk drive system) by creating a write bubble region encroaching on the medium. The write bubble region has a magnetic polarity that is reversed in a pattern that corresponds to the values of the data bits being recorded on the medium. The timing of the reversing of the magnetic polarity of the write bubble region is adjusted by a precompensation system to ensure that the recorded data bits are evenly spaced on the medium. The timing adjustment is made by the precompensation system based on a state of at least one data bit previously recorded on the medium and on a state of at least one data bit to be subsequently recorded on the medium.

Look ahead write precompensation

A pulse-mode data writing protocol is disclosed which reduces the time required to implement a transition in the direction of magnetization of a recording medium, and which reduces the total power required to encode a given data sequence. After a magnetic transition is encoded on the medium by generating a write current pulse through the write head, the write current through the recording head is reduced, thereby utilizing the spatial extent of the write bubble to encode the lack of a transition on the medium. Alternate configurations are disclosed for various scenarios of write bubble size versus maximum cell size, all utilizing the principle of the invention.

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Eden Prairie, MN, United States of America

Carl F Elliott