International Business Machines Corporation

Yoshiro Amano

Nobuyuki Kitazaki

Shinji Ueno

Masahiro Shimizu

Masashi Kisaka

Isao Yoneda

Fuminori Sai

Hiroshi Uchiike

Kenji Ogasawara

Takao Matsui

Yuji Yokoe

Kazushi Tsuwako

Shusuke Kurihara

Tatsuo Shimofusa

Kazuo Hokazono

Tsuyoshi Miura

Kazunari Tsuchimto

Kenjo Ogasawara

A preamplifier circuit to improve the ESD immunity of magnetic recording devices having magnetoresistive (MR) sensors, without degrading the sensor's high-frequency characteristics. The preamplifier circuit is coupled to an MR sensor having one terminal grounded. The preamplifier circuit includes a varistor coupled between a power supply line and a ground terminal. If a high voltage, exceeding the varistor voltage, is applied to the chassis (ground), it is discharged through the varistor between the power supply voltage line and the ground terminal, instead of through the MR head or the arm electronics module. The present invention thereby protects the MR head and the arm electronics module from ESD damage.

Preamplifier circuit with magnetoresistive sensor ESD protection

A disk drive with means to prevent accidental landing of a head/slider on the disk surface is described. In one embodiment a shock sensor is provided to sense external shocks received by the mechanism. During loading (positioning) of the actuator bearing the head/slider over the disk, if a shock is sensed, loading is stopped and an immediate unloading is performed to return the actuator to the withdrawn position. In another embodiment the unload operation is performed when the rotational speed of the disk is changed. In another embodiment the unload operation is performed when the rotational speed of the disk drops below a threshold. A circuit and method for detecting when the rotational speed of the disk drops below a threshold is also provided. The unloading in the various embodiments may be performed using velocity control or without velocity control.

Disk drive with actuator load/unload controller

The present invention is an apparatus and method to reliably unload a head slider from a recording medium. Transistor Tr5 is on. If the main power supply Vdd is turned off at time t1, Tr1, Tr2, and D1 are turned off and the level of the control signal Ret becomes higher than the threshold voltage Vth of Tr3 and Tr4, turning on Tr3 and Tr4. C1 also starts to discharge. The control signal InRet changes to a 'L'-level, and the control signal OutRet remains to be at the 'L'-level. This allows the IR driver to feed a negative-polarity VCM current through the voice coil to preliminarily move the head arm in the direction opposite to the unload direction. Then, at time t2 when the level of Ret becomes equal to or lower than Vth, both InRet and OutRet change to a 'H'-level, the IR driver becomes inoperative, and the OR driver feeds a positive-polarity VCM current through the voice coil to reverse the moving direction of the head arm.

Head mechanism control apparatus, disk drive unit, and method of

A method and apparatus for positioning a head over a track in an information recording medium to eliminate head positioning error. Data tracks are concentrically formed on a magnetic disk, and identification information for identifying each data track is recorded so as to correspond to each data track. The identification information consists of first and second gray codes, and the first gray code is of n-1 bits where n represents the number of bits of a track address and set for each block so that it has a value different among a plurality of blocks each consisting of a plurality of data tracks. The second gray code is of three bits, and set for each data track so that it represents a value which differs between data tracks contiguous in the radial direction of the disk and circulates for every three or more blocks continuous in the radial direction of the disk. Head positioning is determined based on reading the first and second gray codes by the head.

Method and apparatus for determining head positioning in a magnetic disk

In response to a source current supply and a sink current supply, a switching circuit selectively forms a current path through which a constant source current from the source current supply flows into a laser in order to turn on the laser and a current path through which a constant source current from the source current supply flows into the sink current supply in order to turn off the laser.

Laser driver and optical disk drive apparatus

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Yokohama, Japan

Yoshiro Amano