JP2000030230A - Magnetic disk device and grounding method of double stripe magneto-resistive head applied thereto - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a DSMR head from being damaged by preventing a large current from flowing through the MR element from a common terminal of the head, when static electricity is impressed on a magnetic disk device using the DSMR head. SOLUTION: When a current flows into HDA from a ground plane 250 by electrostatic discharge to an outside plane of HDA, an impedance element 300 prevents a large current from flowing through MR element 161x, 161y via a common terminal COM from the ground plane 250, by connecting the impedance element 300 across the common terminal COM of DSMR head 160 and the ground input (GND) 250 of a preamplifier 201 in a preamplifier IC 200, i.e., the ground plane 250 of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive using a double-stripe magnetoresistive head having a pair of magnetoresistive elements for reproducing data from a disk, and a double-stripe magnetoresistive device applied to the same. The present invention relates to a head grounding method.

[0002]

2. Description of the Related Art In recent years, in order to realize a high recording density (high capacity) of a magnetic disk drive, a magnetic resistance (Magneto-Resistant) has been developed.
Magnetic disk devices employing read-only (playback) heads called sistive (MR) heads are increasing. However, in a magnetic disk device using a magnetoresistive head, when a minute projection is present on the disk surface, the reproduction waveform (read signal waveform) is disturbed by heat generated by the head coming into contact (collision) with the projection. That is, the reproduced waveform is D
A thermal asperity (Thermal Asperit) in which the baseline (the center line of the amplitude of the reproduced waveform) shifts in a C-like manner (a change in time of about 1 to 2 μs and a low frequency) shifts.
y; TA), there is a problem that causes a read error and the like.

[0003] Therefore, recently, a double stripe magnetoresistive (Dual S) having a pair of magnetoresistive elements (MR elements) has been proposed.
A magnetic disk device using a tripe magnetoresistive (DSMR head) has emerged.

[0004] As shown in FIG.
Of the pair of MR elements 161x and 161y form signal terminals 162x and 162y for differential output, respectively, and the other ends are connected in common to form a common terminal COM. That is, the DSMR head 160 has three terminals.

The terminals 162x, 1 of the DSMR head 160
62y is connected to the positive side input and the negative side input of the differential type preamplifier (first stage amplifier) 201 in the preamplifier (head amplifier) IC, and the common terminal COM is directly connected to the ground input (GND) of the differential type preamplifier. ing.

In the DSMR head 160, a magnetic disk (magnetic recording medium) is formed by a pair of MR elements 161x and 161y.
And generates a voltage signal corresponding to the resistance change at the signal terminals 161x and 161y. This DSMR
The voltage signals at the terminals 161x and 161y of the head are guided to the positive input terminal and the negative input terminal of the preamplifier 201 and differentially amplified.

At this time, if the signal read from the DSMR head 160 contains a low-frequency fluctuation signal (noise) due to the occurrence of TA, the fluctuation signal is transmitted to the preamplifier 2.
01 appears at the positive input terminal and the negative input terminal as an in-phase signal. Thus, the preamplifier (differential preamplifier) 20
Due to the common mode elimination characteristic at 1, the TA component (noise component) included in the signal (read signal) read from the DSMR head 160 can be attenuated.

[0008]

As described above, the DS
In a magnetic disk drive using an MR head, TA
The in-phase noise component (fluctuating signal) caused by the occurrence is
To some extent due to the differential output of the MR element (MR film) of one (layer),
As compared with the case where a normal MR head having an element is used, the influence of TA generation can be reduced.

[0009] However, the DSMR head has a problem that the MR element is easily broken by electrostatic discharge (ESD). This problem will be described below with reference to FIG.

First, in the magnetic disk drive, the mechanical part including the head and the magnetic disk, that is, the mechanical part (mechanical part) of the head disk assembly (HDA) is all grounded. Therefore, the HDA forms a Faraday cage with respect to the internal mechanical parts such as the head and the magnetic disk.

On the other hand, as shown in FIG.
The common terminal COM of the head 160 is connected to a ground plane 250 (GN
D). The ground plane 250 is not only a ground level of the circuit system but also a ground level of the mechanical system.

When static electricity is applied to a magnetic disk drive having such a structure from a space or through a human body, a current flows through the ground plane 250 due to electrostatic discharge to the outer surface of the HDA, that is, the ground plane 250. As shown by an arrow 130 in FIG. 1, a large current of several tens mA or more flows into the common terminal COM of the DSMR head 160.

Then, currents 131x and 131y of several tens mA or more flow from the common terminal COM to the MR elements 161x and 161y of the DSMR head 160, and the MR elements 16
1x and 161y are destroyed. The reason is that the MR element 16
This is because, when a current of several tens mA or more flows through 1x and 161y, the MR element generates heat and the thin film forming the MR element melts.

On the other hand, the direction of the arrow 140, that is, the ground input (GND) of the preamplifier 201 is
1 has an input impedance of MR elements 161x and 161y
(Less than 60Ω), almost no current flows.

The present invention has been made in consideration of the above circumstances, and has as its object to provide a double stripe magnetoresistive head (DSM).
When static electricity is applied to a magnetic disk device using the (R head), a large current can be prevented from flowing from the common terminal of the head to the MR element, and the head can be prevented from being destroyed. An object of the present invention is to provide a disk device and a method of grounding a double stripe magnetoresistive head applied to the disk device.

[0016]

SUMMARY OF THE INVENTION The present invention is used for reproducing data from a magnetic disk and has a pair of MR elements (magneto-resistance effect elements). A DSMR head (double-stripe magnetoresistive head) which forms an output signal terminal and is connected at the other end to a common terminal, and a positive input and a negative side connected to a pair of signal terminals of the DSMR head. Having an input,
A differential-type first-stage amplifier for differentially amplifying a voltage signal guided to the positive-side input and the negative-side input, and a ground input of the first-stage amplifier is grounded to a ground plane of the device. Wherein the impedance element is connected between the common terminal of the DSMR head and the ground input of the first-stage amplifier.

In such a configuration, the common terminal of the DSMR head is not grounded directly to the ground plane of the device (mechanical system) as in the conventional case, but is grounded via an impedance element. Even if static current flows from the ground plane of the device due to electrostatic discharge of the
The amount of current flowing into the MR element through the common terminal of the R head is smaller than in the related art. Therefore, the DSMR head is resistant to electrostatic discharge (ESD).

Here, the frequency of the impedance element is 0
The relationship between the resistance value R0 of the resistance component at Hz and the resistance value Rf of the resistance component at frequencies other than 0 Hz is preferably Rf> R0. That is, the frequency 0 of the impedance element
Hz, more specifically, 10 MHz which is a typical range of the frequency component of the electrostatic current.
The resistance component at １００100 MHz has a resistance value Rf large enough to reduce the current flowing to the MR element at the time of electrostatic discharge, and the resistance component with respect to DC is to avoid malfunction of the first-stage amplifier with respect to DC component. It is preferable that the frequency characteristics have a resistance value R0 relatively smaller than Rf.

As such an impedance element,
An element in which a resistor and an inductor are connected in series, or a ferrite bead having a resistance component and a reactance component is applicable.

In addition, a configuration may be applied in which a diode element is used as the impedance element, the cathode of which is connected to the ground input of the first-stage amplifier, and the anode of which is connected to the common terminal of the DSMR head.

Here, with respect to the inflow of the electrostatic current from the ground plane due to the electrostatic discharge, the diode element has a high resistance since it is in the reverse connection state, and the electrostatic current flows into the MR element of the DSMR head. Can be prevented. In a normal use state in which the sense current is supplied from the signal terminals of the pair of MR elements, the diode element has a low resistance because it is in a forward connection state with respect to the sense current, and has a low resistance through the first-stage amplifier. There is no adverse effect on detecting a value change.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view showing the internal structure of a magnetic disk drive according to one embodiment of the present invention.

The magnetic disk drive shown in FIG. 1 has a rectangular box-shaped metal case (base) 10 with an open upper surface, and is screwed to the case 10 with a plurality of screws 21 to open the upper end opening of the case 10. Closed metal top cover 11
And The case 10 is electrically grounded, and is at a ground (GND) level.

In the case 10, a spindle motor 13 for supporting and rotating a magnetic disk, for example, three magnetic disks 12 having a diameter of 65 mm (2.5 inches) is provided. Motor shaft 50 of spindle motor 13
Is fixed to the top cover 11 by screws 22 with the opening of the case 10 closed by the top cover 11. The spindle motor 13 has a cylindrical hub 44 functioning as a rotor. The disks 12 are fitted coaxially with each other on a hub 44, and are stacked at predetermined intervals along the axial direction of the hub 44.

A flange 54 functioning as a disc receiving portion is formed on the outer periphery of the lower end of the hub 44. Each disk 12 is fitted on the outer peripheral surface of the hub 44 with the hub 44 inserted through the inner hole 42, and is stacked on the flange 54 along the axial direction of the hub 44. The hub 44
A pair of spacer rings 58 are fitted around the outer circumference of the disk, and are stacked between the upper and middle disks 12 and between the middle and lower disks 12, respectively.

On the upper end surface of the hub 44, a ring-shaped disc holder 60 functioning as a clamp member is fixed by screws with four screws 61. The outer peripheral portion of the disc holder 60 is in contact with the upper surface of the central portion of the upper disc 12, and the three discs 12 and the two spacer rings 5
8 is pressed against the flange 54 of the hub 44.
Thereby, the three disks 12 and the spacer ring 5
8 is clamped between the flange 54 and the disc retainer 60, and is fixed and held to the hub 44 in a state of being in close contact with each other.

In the case 10, a bearing assembly 14 is provided.
And a head stack assembly (hereinafter, HS) rotatably supported around a pivot by the bearing assembly 14.
A) 15 are stored. In the HSA 15, n (here, n = 6) magnetic head assemblies 17 having a magnetic head 16 for recording and reproducing information at the tip are stacked and arranged. In this embodiment, the head 15 is a composite separation type head including a read-only head and a recording-only head. The read-only head has a DSMR
A head is used.

A voice coil motor (hereinafter referred to as VC) for rotating (rotating) the HSA 14 is provided in the case 10.
M) 18 and a flexible printed circuit board (hereinafter, referred to as FPC) 1 on which a preamplifier IC and the like are mounted.
9 is also stored. On the FPC 19, a pattern for connection to a power line, a control signal line, and a head of the preamplifier IC is formed. The coil 35 of the VCM 18 is fixed to the support frame 34 of the HSA 15.

On the outer surface of the case 10, a printed circuit board (hereinafter, referred to as PCB) 20 is screwed with screws 24, and is located opposite the bottom wall of the case 10. The PCB 20 includes a spindle motor 13 and a VCM1.
IC, a read / write IC for performing signal processing necessary for decoding data from a signal reproduced by the magnetic head 16, signal processing necessary for recording data on the magnetic disk 12, and the like. , A disk controller (HDC) for controlling protocol processing for communicating commands and data with the host, read / write control for the magnetic disk 12 through a read / write IC, a CPU for controlling the entire device, and the like ( (Both not shown) are implemented.

The bearing assembly 14 of the HSA 15 is
0 is fixed on the bottom wall and the inner surface of the top cover by screws 23a and 23b. In a state where the HSA 14 is incorporated in the case 10, the coil 35 fixed to the support frame 34
Is located between a pair of yokes fixed on the case 10, namely, a top yoke 36a and a bottom yoke 36b. The magnet (permanent magnet) 37 fixed to the coil 35, the yokes 36a and 36b, and the bottom yoke 36b
M18 is constituted. The VCM 18 rotates the HSA 15 by supplying a current to the coil 35, and the head 16
Is moved on the disk 12 in the radial direction of the disk 12.

As described above, in the magnetic disk drive of FIG. 1, the mechanical portion including the HSA 15 and the disk 12
That is, all the mechanical parts (mechanical parts) of the HDA (head disk assembly) are grounded to the metal case 10. In addition, these HDA mechanism parts are all
When the opening of the case 10 is closed with the metal top cover 11 in a state where the Faraday cage is mounted on the Faraday cage, the inside thereof forms a Faraday cage that is electrically shielded.

FIG. 2 shows a schematic configuration of a DSMR head and a recording head as read-only heads constituting the magnetic head 16 in FIG. 1, and a main circuit configuration of a preamplifier IC connected to the DSMR head and the recording head. FIG. 3 is a block diagram showing a connection relationship between the two. The same parts as those in FIG. 7 are denoted by the same reference numerals.

As shown in FIG.
This is a composite separation type head including the SMR head 160 and the recording head 164. The DSMR head 160
As described with reference to FIG.
A pair of MR elements (magnetoresistive elements) 161x, 161
y. Here, the MR element 161
x and 161y each have a signal terminal 1 for differential output.
62x and 162y, and the other end is commonly connected to form a common terminal COM. That is, the DSMR head 1
60 has three terminals. On the other hand, the recording head 16
4 has signal terminals 165x and 165y.

Preamplifier IC (preamplifier circuit) 200
Represents n sets (here, n = 6) of read signal input terminals R1
x, R1y to Rnx, Rny, n sets of write signal output terminals W1x, W1y to Wnx, Wny, read signal output terminals Rdx, Rdy, write signal input terminals Wdx, Wdy, and serial data input It has a terminal group including a terminal SD, a clock input terminal SCLK, and a ground terminal GND.

The read signal input terminals Rix and Riy (i is 1 to n) of the preamplifier IC 200 are connected to the MR elements 161x,
161y) are connected to the signal terminals 162x and 162y,
The write signal output terminals Wix and Wiy are connected to the head 16
Of the recording head 164 are connected to the signal terminals 165x and 165y.

The ground terminal G of the preamplifier IC 200
The ND is connected to a ground plane (ground level) 250 of the magnetic disk drive of FIG. The ground plane 250 is not only a ground level of the circuit system but also a ground level of the mechanical system. Further, the ground terminal GND of the preamplifier IC 200
And the common terminal COM of the DSMR head 160 of each magnetic head 16, that is, the ground plane 25 of the magnetic disk drive.
0 and the common terminal COM of the DSMR head 160 of each magnetic head 16, an impedance element 300 is connected.

The preamplifier IC 200 is provided with n differential preamplifiers (first-stage amplifiers) 201 as described with reference to FIG. 7 in the section of [Prior Art]. A positive (+) side input and a negative (−) side input of the preamplifier 201 are connected to read signal input terminals Rix and Riy,
The ground input (GND) is connected to the ground terminal GND of the preamplifier IC 200. The ground terminal of the preamplifier IC 200 and the common terminal COM of each DSMR head 160
And the impedance element 300 as described above.
Is connected. Therefore, the impedance element 3
00 is the ground input (GND) of the preamplifier 201 and DS
It is connected between the common terminal COM of the MR head 160.

The preamplifier 201 includes a DSMR head 160 connected to the read signal input terminals Rix and Riy.
Of the DSMR head 1 according to the voltage signals of the signal terminals 162x and 162y, ie, the magnetic flux leaking from the magnetic disk 12.
The signals reproduced by the MR elements 161x and 161y in 60 (voltage signals at the terminals 162x and 162y corresponding to the resistance change of the MR elements 161x and 161y) are differentially amplified. The output of each preamplifier 201 is guided to each input of a differential buffer amplifier 202. Buffer amplifier 202
Amplifies the output signal of the preamplifier 201 selected by the sense current control circuit 206 described later.

The output of the buffer amplifier 202 is output to a read / write IC (not shown) via read signal output terminals Rdx and Rdy. The read / write IC performs signal processing required for reproducing an output signal (read data signal) of the buffer amplifier 202 into, for example, NRZ code data, signal processing required for recording information on the magnetic disk 12, and the like.

The preamplifier IC 200 has a read /
A write pre-driver 203 for amplifying a write data signal sent from the write IC via the write signal input terminals Wdx and Wdy is provided. The output of the write pre-driver 203 is guided to the inputs of the n write drivers 204. The write driver 204 outputs a write current corresponding to the output (polarity) of the write pre-driver 203 when selected by a write current control circuit 208 described later. The output of the write pre-driver 203 is output to the signal terminals 165x and 165y of the recording head 164 in the magnetic head 16 via the write signal output terminals Wix and Wiy.

The preamplifier IC 200 also includes a DSM corresponding to any one of the n preamplifiers 201.
A sense current source 205 for generating and outputting a sense current supplied to the R head 160 and a sense current from the sense current source 205 are designated from outside (a CPU (not shown) controlling the entire magnetic disk device of FIG. 1). And a sense current control circuit 206 for selectively supplying the preamplifier 201 corresponding to the head 16 that has been provided.

The preamplifier IC 200 further selectively supplies a write current source 207 for generating and outputting the write current and a write current from the write current source 207 to a write driver 204 corresponding to the head 16 designated by the CPU. A write current control circuit 208 to be supplied and a serial interface 209 for exchanging data with the CPU
Are provided.

The serial interface 209 is a CPU
, And serial data (control data) for controlling the preamplifier IC 200 which is transferred to the serial data input terminal SD in accordance with a clock signal which is guided to the clock input terminal SCLK. Source 205, sense current control circuit 20
6, and the preamplifier 201 or the write current source 20
7. The write current control circuit 208 and the write driver 204 are controlled.

In the magnetic disk drive having the above-described configuration, as described above, the mechanical portion including the HSA 15 and the disk 12, that is, the mechanical portion (mechanical portion) of the HDA (head disk assembly) is all grounded to the metal case 10. Have been. When the opening of the case 10 is closed by the metal top cover 11, the inside is electrically shielded.

When static electricity is applied to the magnetic disk device in such a state from a space or through a human body,
When an electrostatic discharge (ESD) occurs on the outer surface of the HDA, that is, the ground plane 250 and a current flows through the ground plane 250, the MR elements 161x,
The current flowing through 161y will be described with reference to FIG.

First, the MR element 1 of the DSMR head 160
61x, 161y, one terminal of each of the signal terminals 165x, 16
5y is connected to the positive side input and the negative side input of the corresponding preamplifier 201 in the preamplifier IC 200 (via the read signal input terminals Rix and Riy of the preamplifier IC 200). Also, the MR element 16 of the DSMR head 160
Common terminal COM which is a common connection terminal for 1x and 161y
Are connected to the ground plane 250 and the ground input (GND) of the preamplifier 201 via the impedance element 300.

Therefore, when a current flows through the ground plane 250 due to the electrostatic discharge to the ground plane 250 as described above, as shown in FIG.
0, that is, a current flows from the ground plane 250 to the ground input (GND) of the preamplifier 201, and in the direction of arrow 310 through the impedance element 300, that is, D
The current also flows into the common terminal COM of the SMR head 160. Thereby, the MR element 16 is connected from the common terminal COM.
Currents 311x and 311y flow through 1x and 161y.

However, in this embodiment, the ground plane 250 (GN
D) and the ground input (GND) of the preamplifier 201, that is, the ground level and the common terminal CO of the DSMR head 160.
Since the impedance element 300 is inserted between the MR element 161x and M, the resistance component on the DSMR head 160 side as viewed from the ground plane 250 is larger than that in the related art in which the impedance element 300 is not inserted.
The values of the currents 311x and 311y flowing through 61y are the same as those of the MR elements 161x and 161 in [Prior Art] shown in FIG.
1y) (smaller than currents 131x and 131y flowing through 1y).

As the impedance element 300, for example, an element in which a resistor and an inductor are connected in series as shown in FIG. 4A, or a ferrite bead having a resistance component R and a reactance component X as shown in FIG. Applicable.

The impedance element 300 has a relatively small resistance value R0 (Ω) with respect to direct current (frequency = 0 Hz) in order to avoid malfunction of the preamplifier 201. 0 Hz), the current flowing into the MR elements 161x and 161y of the DSMR head 160 due to electrostatic discharge can be reduced in the range of the frequency component of the electrostatic current (usually 10 MHz to 100 MHz). Thus, it is preferable that the frequency characteristics have a resistance value Rf (Ω) larger than R0.

In particular, the MR element 1 of the DSMR head 160
By calculating the resistance value based on the value of the sense current supplied to 61x and 161y and the output of the preamplifier 201, the MR
In a magnetic disk drive to which a method of detecting a short circuit (open circuit) / open circuit (open circuit) of the elements 161x and 161y is applied, the resistance value R0 at direct current (frequency = 0 Hz) is set so that the detection accuracy does not decrease. Preferably, a lower impedance element 300 is used.

FIG. 5 shows an example of the frequency characteristic of the impedance of the impedance element 300 (ferrite bead) when the ferrite bead shown in FIG. 4B is used as the impedance element 300. In this example, the resistance component R of the impedance element 300 (ferrite bead) has a small value of 20Ω or less at 1 MHz or less out of the range of the frequency component of the electrostatic current, whereas In the range of the components (10 MHz to 100 MHz), the value is as large as about 40 to 80 Ω.

The impedance element 3 having the frequency characteristic shown in FIG.
00 is the common terminal COM of the DSMR head 160 and the ground input (GN) of the preamplifier 201 as shown in FIG.
D), that is, in the magnetic disk device inserted between the ground surface 250 and the electrostatic discharge on the outer surface of the HDA, when the MR element 161x,
The waveform of the current flowing through the impedance element 161y is
6 in comparison with the prior art (see FIG. 7) that does not use 00.
Shown in

FIGS. 6A to 6D are current waveform diagrams of the present embodiment using the impedance element 300, and FIGS.
(F) is a current waveform diagram of the prior art without using the impedance element 300. 6 (a) is at 130V electrostatic discharge, FIG. 6 (b) is at 150V electrostatic discharge, FIG. 6 (c) is at 200V electrostatic discharge, and FIG.
6E shows current waveforms at the time of electrostatic discharge of 0 V, FIG. 6E shows current waveforms at the time of electrostatic discharge of 100 V, and FIG.

As is apparent from the figure, according to the present embodiment, the MR elements 161x, 161 of the DSMR head 160
The maximum current flowing in y becomes smaller than that of the conventional technology at the time of 100 V electrostatic discharge even when, for example, an electrostatic discharge of 200 V occurs. Although not shown in the drawing, in the present embodiment, in an electrostatic discharge of 120 V or less, current flows only to the ground input (GND) side of the preamplifier 201, and hardly flows to the MR elements 161x and 161y.

Incidentally, the impedance element 300 is not limited to the series circuit composed of the resistor and the inductor shown in FIG. 4A, or the ferrite bead shown in FIG. 4B. The diodes shown are also applicable.

When the diode shown in FIG. 4C is used as the impedance element 300, the cathode of the diode is connected to the ground input (GN) of the preamplifier 201.
D), that is, connected to the ground plane 250 and the anode is connected to the DSM
It is necessary to connect to the common terminal COM of the R head 160.

When used in this manner, the diode has a high resistance since it is in a reverse connection state with respect to the electrostatic current from the ground plane 250, and the static current becomes D
The flow is prevented from flowing into the MR elements 161x and 161y of the SMR head 160. Further, the sense current is supplied to the MR element 16.
In a normal use state supplied from the signal terminals 162x and 162y of 1x and 161y, the sense current is in a forward connection state and therefore has a low resistance.
1 does not adversely affect the detection of the change in the resistance value of the MR elements 161x and 161y.

In addition, a resistor shown in FIG. 4D may be used as the impedance element 300. However, if a resistor having a large resistance value is used, a malfunction of the preamplifier 201 may be caused.
It is necessary to lower the resistance value as compared with the case where the element shown in (c) is used. In this case, the current flowing through the MR elements 161x and 161y of the DSMR head 160 during the electrostatic discharge is smaller than that of the related art, however, FIG.
This is larger than the case where the element shown in (c) is used.

[0060]

As described in detail above, according to the present invention, D
A ground input of a preamplifier (first-stage differential amplifier) for differentially amplifying a voltage signal at each end of a pair of MR elements of the SMR head;
That is, by inserting an impedance element between the ground level of the apparatus and the common terminal of the DSMR head (the common terminal to which the other end of the pair of MR elements is connected in common), the current is discharged from the ground level by electrostatic discharge. Even when the current flows, a large current can be prevented from flowing through the MR element via the common terminal of the head, and the head can be prevented from being destroyed.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing the internal structure of a magnetic disk drive according to an embodiment of the present invention.

FIG. 2 is a schematic configuration of a DSMR head and a recording head as read-only heads constituting a magnetic head 16 in FIG. 1,
FIG. 2 is a block diagram showing a main circuit configuration of a preamplifier IC connected to the DSMR head and the recording head, together with a connection relationship between the two.

FIG. 3 is a diagram showing a connection relationship including an impedance element 300 between a DSMR head 160 and a preamplifier 201 and a path of a current flowing during electrostatic discharge in the embodiment.

FIG. 4 is a diagram showing a specific example of an impedance element 300.

FIG. 5 is a diagram showing an example of the frequency characteristic of the impedance of the impedance element 300 (ferrite bead) in FIG. 4B.

6 is an MR element 161 of the DSMR head 160 at the time of electrostatic discharge in a magnetic disk device to which the impedance element 300 (ferrite bead) having the characteristic shown in FIG. 5 is applied.
FIG. 9 is a diagram showing waveforms of currents flowing through x and 161y in comparison with a conventional technology that does not use the impedance element 300.

FIG. 7 is a diagram showing a connection relationship between a DSMR head 160 and a preamplifier 201 in a conventional magnetic disk device, and a path of a current flowing during electrostatic discharge.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Case 11 ... Top cover 12 ... Magnetic disk 15 ... HSA (head stack assembly) 16 ... Magnetic head 160 ... DSMR head (double stripe magnetoresistive head) 161x, 161y ... MR element (magnetoresistive element) 162x, 162y ... Signal terminal 164 ... Recording head 200 ... Preamplifier IC 201 ... Preamplifier (differential preamplifier, differential first stage amplifier, first stage differential amplifier) 250 ... ground plane 300 ... impedance element COM ... common terminal

Claims (6)

[Claims] 1. A method for reproducing data from a magnetic disk, comprising a pair of magnetoresistive elements, one end of each of the pair of magnetoresistive elements forms a signal terminal for differential output, and the other end. Has a double-stripe magnetoresistive head connected in common to form a common terminal, a positive input and a negative input connected to the pair of signal terminals of the double-stripe magnetoresistive head, and has a ground input. A magnetic disk having a differential-type first-stage amplifier for differentially amplifying a voltage signal guided to the positive-side input and the negative-side input, wherein a ground input of the first-stage amplifier is grounded to a ground plane of the device. A magnetic disk drive, comprising: an impedance element connected between the common terminal of the double stripe magnetoresistive head and a ground input of the first-stage amplifier. 2. The frequency of the impedance element is 0H.
2. The magnetic disk drive according to claim 1, wherein the relationship between the resistance value R0 of the resistance component at z and the resistance value Rf of the resistance component at a frequency other than 0 Hz is Rf> R0. 3. The magnetic disk drive according to claim 2, wherein the impedance element is an element in which a resistor and an inductor are connected in series. 4. The magnetic disk drive according to claim 2, wherein said impedance element is a ferrite bead having a resistance component and a reactance component. 5. The device according to claim 1, wherein the impedance element is a diode element, a cathode of which is connected to a ground input of the first-stage amplifier, and an anode of which is connected to the common terminal of the double-stripe magnetoresistive head. 2. The magnetic disk drive according to claim 1, wherein: 6. A method for reproducing data from a magnetic disk, comprising a pair of magnetoresistive elements, one end of each of the pair of magnetoresistive elements forms a signal terminal for differential output, and the other end. Has a double-stripe magnetoresistive head connected in common to form a common terminal, a positive input and a negative input connected to the pair of signal terminals of the double-stripe magnetoresistive head, and has a ground input. A differential-type first-stage amplifier for differentially amplifying a voltage signal guided to the positive-side input and the negative-side input, wherein a ground input of the first-stage amplifier is grounded to a ground plane of the device. A method of grounding a double-stripe magnetoresistive head applied to a disk drive, comprising connecting an impedance element between the common terminal of the double-stripe magnetoresistive head and a ground input of the first-stage amplifier. And a double stripe magnetoresistive head of the grounding method which is characterized in that the common terminal of the dual stripe magnetoresistive head so as to ground through the impedance element.