International Business Machines Corporation

Mark Andrew Bergquist

Richard Leo Galbraith

Anthony Richard Bonaccio

Jonathan Darrel Coker

Earl Albert Cunningham

Mark David Hagen

David Timothy Flynn

Rick Allen Philpott

David James Stanek

Thomas C Christensen

David Peter Swart

Jodie Ann Christner

Kirk W Lang

Dennis E Noltee, Sr

Brian T Ashelin

Anthony John Perr

Methods and apparatus are provided for detecting servo information in a direct access storage device. A plurality of data symbols are read from a disk to produce a readback signal. Each data symbol and each sequence of data symbols contains servo identification information. A correlation filter provides a matched filter function of an expected readback signal of the plurality of data symbols to produce a correlated readback signal. A threshold detector is coupled to the correlation filter for identifying a threshold signal representative of the data symbol. A data separator responsive to the threshold detector windows the threshold signal and provides clock and data signals. The data separator includes a digital variable frequency oscillator (VFO) which optimally centers incoming servo information from the disk in a timing window and provides standard clocked data for a servo processor. The threshold detector has a variable threshold voltage that is programmed using a trim digital-to-analog converter (DAC).

Method and apparatus for servo data pattern detection

A method and apparatus is provided which introduces a relative skew between a servo pattern and a magneto-resistive (MR) head in order to reduce interference introduced by inductive reading of shields formed as part of the MR head. The relative skew may be accomplished by introducing a skew angle directly on the head or by skewing the servo pattern formed on the magnetic medium relative to the head. Various skewed patterns may be used to reduce the overall interference.

Method and apparatus for reducing servo interference in a

A peak detector having several novel detection modes including detecting a pair of peaks with opposite polarity and selecting whether or not the peaks must cross programmed thresholds to be detected. The novel detection modes together with several known detection modes are provided in one unit and can be selected by the user. A power down feature is also provided.

Multiple mode peak detector

An analog output buffer circuit having a low quiescent power dissipation and a high current-driving capability is disclosed. In accordance with a preferred embodiment of the present invention, the analog output buffer circuit includes a capacitor and three transistors. The first transistor is coupled between a power supply and an output. The gate of the first transistor is utilized for receiving input signals. The second transistor is coupled between the output and ground. The capacitor is coupled between a gate of the first transistor and a gate of the second transistor such that voltages at the gate of the first transistor are related to voltages at the gate of the second transistor via the capacitor. Finally, the third transistor is coupled between the gate of the second transistor and a current source. This configuration allows the analog output buffer circuit to have a high current-driving capability while maintaining a low power dissipation during the quiescent period.

Analog output buffer circuit

Engineering changes (EC) for an integrated-circuit (IC) module or circuits connected to an IC module sometimes require the addition of discrete electrical components or circuit chips. Such engineering changes are implemented herein on a small printed circuit card or board that may be physically attached to the top of the IC module. The EC pads on the printed circuit EC card are juxtaposed with the IC module input/output (I/O) pins that require the engineering change. A short fly wire is then soldered between each juxtaposed EC pad and the I/O pin to make the electrical connection between the EC card and the module. In this way, no additional surface area is consumed on the printed circuit board on which the module is mounted.

Method and apparatus for implementing engineering changes for integrated

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Rochester, MN, United States of America

Mark Andrew Bergquist