Hewlett-packard Company

Avago Technologies General IP (singapore) Pte. Ltd.

Colorado Memory Systems, Inc.

Ronald R Kennedy

Charles E Moore

Alvin Leng Sun Loke

James Oliver Barnes

Robert Keith Barnes

Mark E Nash

Daniel J Curran

Michael M Oshima

Prabodh L Shah

A phase-locked loop includes a voltage-controlled oscillator and a charge-pump loop filter. The voltage-controlled oscillator includes a varactor having a first set of capacitor cells configured to adjust a capacitance based on a first control voltage, and a second set of capacitor cells configured to adjust a capacitance based on a second control voltage. The charge-pump loop filter receives a first and a second update signal, each having at least one state based on a phase difference between a first clock and a second clock, and comprises a first component and a second component. The first component is configured to adjust, during an update period, a voltage across an impedance from a reference level based on the states of the first and second update signals and to return the voltage across the impedance to the reference level prior to an end of the update period, wherein the voltage across the impedance comprises the first control voltage. The second component is configured to adjust a voltage across a capacitor based on the states of the first and second input signals, wherein the voltage across the capacitor comprises the second control voltage.

Low-jitter charge-pump phase-locked loop

A method and apparatus for using a varying amplitude data signal from a data storage medium such as a magnetic disk or magnetic tape to calibrate the gain of the data signal amplifier to an optimal fixed gain. At initialization, amplified data signal peaks are detected over a data region of the data storage medium. The amplified signal peaks are compared to a predetermined reference. The signal amplifier gain is adjusted until only a few amplified signal peaks exceed the reference. The amplifier gain is then fixed at the final adjusted value.

Using recorded data for auto calibration of fixed gain of a read

A data storage system such as a tape drive or flexible disk drive having a dual-gap head being controlled by a dual-mode flexible disk controller. The flexible disk controller has a first mode designed to use a head having one section for perpendicular reading and writing and a second section for erasing. The flexible disk controller has a second mode designed to use a conventional flexible disk head having a single gap for reading, writing and erasing. The data storage system has a head which has one relatively long gap optimized for overwrite/erase capability and a separate shorter read-only gap optimized for reading high bit densities. The data storage system uses the flexible disk controller in its first mode for formatting and writing and in its second mode for reading. When the controller is being used in a perpendicular recording mode, the head design with the write section offset from the erase section requires extended formatted sector fields. The data storage system takes advantage of these extended formatted data sector fields to accommodate a dual-gap head with an offset between the read gap and the write gap.

Data storage system with a dual-gap head using a dual-mode flexible disk

A programmable filter for the read channel of a magnetic recording device filters the sensed signals corresponding to data on magnetic media at at least two different transfer speeds of the magnetic media. The programmable filter, under microprocessor control, selectively switches its filter characteristics without affecting the quality of the filter but changing the cut-off frequency so as to correspond to the two different transfer speeds. The programmable filter of the present invention utilizes solid state switches to implement the switching of the filter characteristics to change the cut-off frequency without affecting the quality. The programmable filter is inductorless and is designed only with resistors and capacitors arranged in a filter network. The programmable filter does not use operational amplifiers, using instead low cost transistors in an emitter-follower configuration. The cut-off frequency of the filter is changed by adding resistance or capacitance in series or in parallel with existing resistances and capacitances in the resistor-capacitor network so as to change the cut-off frequency without affecting the quality. The programmable filter of the present invention provides pulse slimming thereby reducing intersymbol interference, provides sharp roll-off characteristics to minimize higher frequency noise, and produces a voltage output corresponding to the sensed data signals as well as a differentiated voltage output having the identical delay as the voltage output.

Programmable filter/equalizer for duel speed and density magnetic

Growing community of inventors

Fort Collins, CO, United States of America

Ronald R Kennedy