Stmicroelectronics Gmbh

Giuseppe Patti

Roberto Alini

Axel Alegre De La Soujeole

Gilles P DeNoyer

Francesco Rezzi

Elango Pakriswamy

Eugene C Lee

Gilles Denoyer

A system and method for selecting between two biasing modes for biasing magneto resistive heads in a disk drive. A mode selector selects either a voltage biasing circuit or a current biasing to supply the bias voltage or bias current, respectively, to a magneto resistive head. The selection can be based on changes in parameters in the disk drive or magneto resistive heads during disk drive operation.

Bimodal biasing of magneto resistive heads

A method and circuit are disclosed for controlling the write head of a magnetic disk storage device. The circuit includes a pull-up device coupled to a terminal of the write head, a current sink circuit which is coupled to the write head terminal and a bootstrap circuit coupled to the current sink circuit. When reversing the direction of current flow through the write head so that current is drawn from the write head from the write head terminal, the bootstrap circuit and the current sink circuit are activated. When the current in the write head nears and/or slightly surpasses the desired destination current level, the bootstrap circuit is deactivated and the pull-up device is thereafter immediately activated for a predetermined period of time.

Circuit and method for writing to a memory disk with a boosted voltage

A method and circuit are disclosed for controlling the write head of a magnetic disk storage device. The circuit includes a pull-up device and a current sink circuits coupled to each terminal of the write head, for selectively sourcing current to and sinking current from the write head, respectively. A clamp device is coupled to each write head terminal to selectively clamp the write head terminals to steady state intermediate voltage levels. The circuit further includes a control circuit for individually activating the pull-up devices, the current sink circuits and the clamp devices. In particular, when reversing the direction of current flow through the write head from a first direction in which current is provided to the write head via the write head terminal to a second direction in which current is drawn from the write head from the write head terminal, the appropriate pull-up device is activated for a predetermined period of time. The clamp device coupled to the temporarily activated pull-up device is thereafter activated to clamp the corresponding write head terminals to the steady state intermediate voltage levels.

Write head driver circuit and method for writing to a memory disk

An apparatus (and method) is provided that reduces thermal interference in the read signal of a disk drive. A variable or programmable resistance is used to change the transfer function of a filter in the read channel of the disk drive to filter the read signal. The filter has a first transfer function (first cut-off frequency) related to the programmed resistance during normal operation of the disk drive (i.e. when thermal interference is not detected). When thermal interference is detected in the read signal, the resistance is programmed to another value resulting in the filter having a second transfer function (second cut-off frequency). The resistance element includes a transconductance amplifier whose transconductance is variable or programmable to different values resulting in different programmable transfer functions (or one of a multitude of cut-off frequencies) for the filter. In the preferred embodiment, detection of thermal interference increases the cut-off frequency of the filter thereby filtering, or reducing the effects of, the thermal interference in the read signal.

Apparatus and method for reducing thermal interference in MR heads in disk drives

A method and circuit are disclosed for controlling the write head of a magnetic disk storage device. The circuit includes a pull-up device coupled to a terminal of the write head, for selectively providing a current to the write head though the write head terminal. The circuit further includes parallel-connected current sink circuits, each of which is coupled to the write head terminal and selectively activated to draw current from the write head via the write head terminal. A first transistor is connected in series between the pull-up device and the write head terminal and biased to provide a voltage differential between the write head terminal and the pull-up device. A second transistor is connected in series between the write head terminal and the current sink circuits and biased to provide a voltage differential between the write head terminal and the current sink circuits.

Circuit and method for writing to a memory disk

An apparatus (and method) is provided that reduces thermal interference in the read signal of a disk drive. A variable or programmable resistance is used to change the transfer function of a filter in the read channel of the disk drive to filter the read signal. The filter has a first transfer function (first cut-off frequency) related to the programmed resistance during normal operation of the disk drive (i.e. when thermal interference is not detected). When thermal interference is detected in the read signal, the resistance is programmed to another value resulting in the filter having a second transfer function (second cut-off frequency). The resistance element is variable or programmable to different values resulting in different programmable transfer functions (or one of a multitude of cut-off frequencies) for the filter. In the preferred embodiment, detection of thermal interference increases the cut-off frequency of the filter thereby filtering, or reducing the effects of, the thermal interference in the read signal.

A system and method for selecting between two biasing modes for biasing magneto resistive heads in a disk drive. A mode selector selects either a voltage biasing circuit or a current biasing circuit to supply the bias voltage or bias current, respectively, to a magneto resistive head. The selection can be based on changes in parameters in the disk drive or magneto resistive heads during disk drive operation.

A method and circuit is disclosed for controlling the write head of a magnetic disk storage device. The circuit includes a pull-up device coupled to a terminal of the write head, for selectively providing a current to the write head through the terminal. The circuit further includes parallel-connected first and second current sink circuits, each of which is coupled to the write head terminal and selectively activated to draw current from the write head via the write head terminal. The circuit further includes a control circuit for individually activating the pull-up device and the first and second current sink circuits. In particular, when reversing the direction of current flow through the write head from a first direction in which current is provided to the write head via the write head terminal to a second direction in which current is drawn from the write head from the write head terminal, both the first and second current sink circuits are activated by the control circuit. When the current in the write head nears the desired destination current level, the second current sink circuit is deactivated and the pull-up device is thereafter immediately activated for a predetermined period of time. The pull-up device is deactivated as the current in the write head approaches a constant value. Due to the deactivation of the second current sink circuit and the temporary activation of the pull-up device, current overshoot and undershoot of the write head current is minimized.

A method and a circuit for correcting asymmetry in a response signal generated by a magneto-resistive head. The magneto-resistive head generates a response signal to transmit digital information read from a magnetic media storage device. The asymmetry is corrected in a negative feedback manner by squaring an output signal, modulating the squared output signal, and subtracting the modulated squared output signal from the response signal to generate the output signal. The circuit employs a differential amplifier as an input stage and a Gilbert multiplier circuit to square the output signal.

Asymmetry correction for a read head

A low noise preamplifier design which is configured such that the current through the first stage load resistor may be made relatively small in value making it possible to achieve a relatively large gain in the first stage thereby reducing the noise contribution of the load resistor and, concurrently, significantly reducing the noise contribution of the second stage as well. This is effectuated by supplying a substantially fixed amount of current to certain nodes in the first stage of the preamplifier through a pair of current sources, the currents being of an amount sufficient to subtract out the bias current that is applied through a series connected variable resistance, such as that of a magnetoresistive ('MR') read head. As a consequence, only a relatively small amount of current is actually fed through the load resistor, and its value may be increased to provide an increased gain for the first stage. Therefore, the noise contribution of the load resistor and the second stage may be rendered relatively negligible.

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San Jose, CA, United States of America

Giuseppe Patti