International Business Machines Corporation

Hitachi Global Storage Technologies Netherlands B.v.

Jacobus Cornelis Leonardus Van Peppen

Klaas Berend Klaassen

John Thomas Contreras

Klaassen Berend Klaassen

Raymond Alan Richetta

Stephen A Jove

Paul Wingshing Chung

Robert Andrew Kertis

Jaydip Bhaumik

John Thomas Conteras

In one illustrative example disclosed, a magnetic storage device includes at least one magnetic disk; a magnetic head which includes first and second read sensors; a suspension which supports the magnetic head relative to the magnetic disk; and read circuitry which includes a preamplifier. The preamplifier has a first input port coupled to the first read sensor; a second input port coupled to the second read sensor; a first bias source coupled to the first input port for actively current/voltage biasing the first read sensor; a second bias source coupled to the second input port for zero biasing the second read sensor; and a subtractor having first and second inputs coupled to the first and the second input ports, respectively. The first input of the subtractor is provided with a first signal which includes a read sensor data signal and an interference signal, whereas the second input of the subtractor is provided with a second signal which includes the interference signal but not the read sensor data signal. Thus, an output of the subtractor provides a read sensor signal without the interference signal.

Preamplifier circuit with signal interference cancellation suitable for use in magnetic storage devices

The spacing decrease between pole tips of a write element and a magnetic medium that is associated with the write element is linearly proportional to an input signal, such as an input voltage or current, to a slider flying height controller for a hard disk drive. The flying height controller includes a heater current controller and a multiplexer. The heater current controller receives the input signal and outputs a control current proportional to the input signal. The multiplexer couples the control current to a heating element associated with the write element on a selected slider body during a read operation. The heating element dissipates a power that is proportional to the control current and causes a decrease in the spacing between the pole tips of the write element and the magnetic medium that is linearly proportional to the control current and to the input signal.

Circuitry for linear control of head flying height using thermal means

A method (and magnetic recording circuit structure) for write drivers to reduce the reversal time for the current through the inductive recording head, includes a write driver output stage providing a write signal output with a write signal source strength S , a magnetic write head with a write signal input essentially equal to strength S , and an interconnect circuit having a characteristic impedance Z coupled to the write signal output of the write driver output stage and the magnetic write head. The write driver output stage preferably includes a source-side termination circuit having output impedance Z , wherein the source-side termination circuit output impedance Z is substantially equal to Z and the source strength S of the write driver at the input of the interconnect circuit is temporarily enlarged after every polarity reversal of the write signal for a predetermined time duration &Dgr;t.

Characteristically terminated write driver with compensation for magnetic response and method therefor

An interconnect circuit for a readout channel front-end for a disk drive is disclosed that includes a forward line and a return line. Both the forward line and the return line have a first end and a second end. The first end of both the forward line and the return line is connectable to a magnetoresistive head. The second end of both the forward line and the return line is connectable to a single-ended preamplifier. The return line is arranged to be disposed between the forward line and a suspension for a magnetoresistive head. The forward trace has a first predetermined width and the return trace has a second predetermined width that can be the same or different from the first predetermined width. When the interconnect circuit is in a disk drive, the first end of the forward line is connected to a magnetoresistive head, and the second end of the forward line is connected to a single-ended preamplifier. Similarly, the first end of the return line is connected to the magnetoresistive head, and the second end of the return line is connected to the single-ended preamplifier. The return line is disposed between the forward line and a suspension for the magnetoresistive head. The characteristic impedance of the interconnect circuit is selected to be about equal to an input resistance of the single-ended preamplifier. Accordingly, the high-frequency roll-off of a transfer characteristic of the interconnect circuit is primarily determined by a high-frequency skin-effect loss in each of the forward and return lines, and the transfer characteristic of the interconnect circuit does not exhibit a &frac14; wavelength effect notch.

Integrated trace suspension interconnect for high-data-rate single-ended preamplifier for (G)MR elements

A magnetic recording channel front-end for a magnetic storage system includes a magnetoresistive element, an interconnect and a readback amplifier. The interconnect, which has a characteristic impedance, couples the magnetoresistive element to the readback amplifier. The readback amplifier includes a gain stage and an active termination. The gain stage, which has an associated impedance, has an input that is connected to the interconnect. The active termination is coupled to the input of the gain stage, such that an input impedance of the readback amplifier, which is formed by a combination of the impedance associated with the gain stage and the active termination, is substantially equal to the characteristic impedance of the interconnect. Additionally, the gain stage generates a first noise signal that has a first magnitude appearing at an output of the gain stage. The active termination generates a second noise signal that has a second magnitude that also appears at the output of the gain stage. The second magnitude is significantly less that the first magnitude, thereby the signal-to-noise ratio performance of the magnetic recording channel front-end is not adversely affected. When the gain stage is a current-sensing gain stage, the active termination provides positive feedback from the gain stage to the input of the gain stage. When the gain stage is a voltage-sensing gain stage, the active termination provides negative feedback from the gain stage to the input of the gain stage.

Wideband readout of magneto-resistive heads for data storage

A method and system for providing a current-sensing preamplifier for use with a magnetoresistive sensor is disclosed. The method includes providing at least one input device coupled with the magnetoresistive sensor, providing a gain stage, and providing a feedback circuit. In a system aspect, the current-sensing preamplifier includes at least one input device. The at least one input device is coupled with the magnetoresistive sensor through an interconnect having a characteristic impedance. The at least one input device provides an input impedance for the current-sensing preamplifier. The current-sensing preamplifier also includes a gain stage coupled with the at least one input device and a feedback circuit coupled with the gain stage and the at least one input device. The feedback circuit provides at least one signal to the at least one input device. The at least one signal controls the input impedance based on at least one error signal.

Quasi-current sensing input impedance controlled preamplifier for magnetoresistive elements

A circuit arrangement for correcting magneto-resistive head asymmetry includes a shift circuit which receives a read signal from a magneto-resistive head, and a polarity signal indicative of the polarity of any asymmetry of the read signal. Depending on the polarity of the asymmetry, the shift circuit either adds or subtracts a shift voltage to the read signal to produce a shifted read signal. The shift circuit outputs the read signal, the shifted read signal, and the shift voltage. First, second and third gain circuits are provided, which receive the read signal, the shifted read signal, and the shift voltage, respectively, and which each receive a respective control signal. The first, second and third gain circuits provide respective outputs amplified proportionally based on the respective control signals. Control circuitry provides the polarity signal to the shift circuit and the respective control signals to the first, second and third gain circuits, based on an amount of correction required. A common-mode-feedback circuit adjusts for changes in the common-mode caused by the waveform shaping.

Magneto-resistive asymmetry correction circuit

A magnetic recording circuit includes a write driver output stage, a magnetic write head and an interconnect circuit. The write driver output stage has an output and an output impedance. The magnetic write head has an input and an input impedance. The interconnect circuit has an input, an output and a selected characteristic impedance Z,. The input of the interconnect circuit is coupled to the output of the write driver output stage, the output of the interconnect circuit is coupled to the input of the write head. The interconnect circuit can be one of, or both, source-terminated so that the output impedance of the write driver output stage is substantially equal to the selected characteristic impedance Z,of the interconnect circuit, and load-terminated so that the input impedance of the write head is substantially equal to the characteristic impedance Z,of the interconnect circuit.

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San Jose, CA, United States of America

Jacobus Cornelis Leonardus Van Peppen