Dynamic magnetic information storage or retrieval – General recording or reproducing – Specifics of the amplifier
Reexamination Certificate
1998-06-26
2001-09-18
Neal, Regina Y. (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Specifics of the amplifier
C360S046000
Reexamination Certificate
active
06292321
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a drive circuit for a magnetic recording device. More particularly, the present invention relates to a drive circuit for a magnetic hard disk drive.
BACKGROUND OF THE INVENTION
FIG. 6
a
illustrates a conventional drive circuit
15
for driving a magnetic hard disk drive. As shown in the figure, the drive circuit
15
is connected to magnetic heads
3
to
6
. The magnetic heads
3
and
4
are respectively disposed near the upper and lower surfaces of a first disk
1
, and the magnetic heads
5
and
6
are respectively disposed near the upper and lower surfaces of a second disk
2
. The disks
1
and
2
rotate around a rotary shaft
7
, and thus, the heads
3
to
6
are capable of selectively writing and reading data to and from the surfaces of the disks
1
and
2
. Generally, the magnetic heads
3
to
6
are respectively provided at the tips of swing arms (not shown) to move the heads
3
to
6
in the radial direction of the disks
1
and
2
when the swing arms move within a movable range
9
. The drive circuit
15
is provided in the vicinity of the swing arms and is typically connected to the magnetic heads
3
to
6
via wires which have lengths of several centimeters. Thus, the drive circuit
15
is capable of reading and writing data to and from the disk by outputting and receiving signals to and from the heads
3
and
6
via the wires. Also, the drive circuit
15
is connected to an input/output signal bus
8
so that it can exchange signals with an external circuit such as read channel LSI.
FIG. 6
b
is a block diagram showing an example of the interaction between a CPU
100
, a read channel LSI (i.e. a control circuit)
102
, and the drive circuit
15
. The CPU
100
exchanges data and commands with the read channel LSI
102
, and the read channel LSI
102
inputs or outputs various signals to and from the drive circuit
15
.
FIG. 7
illustrates the detailed configuration of the conventional drive circuit
15
shown in
FIG. 6
a
and the various signals it receives from and transmits to the read channel LSI
102
. As shown in the figure, the circuit
15
comprises a read/write circuit
200
, a read postamplifier
23
, a read/write switching circuit
34
, a head selection circuit
35
, and a write current generation circuit
36
. Also, the read/write circuit
200
comprises write drivers
26
to
29
and read preamplifiers
30
to
33
. In addition, the magnetic heads
3
to
6
respectively contain write heads
3
a
to
6
a
and read heads
3
b
to
6
b.
When data is written to a disk (e.g. the disk
1
) via a particular write head (e.g. write head
3
a
), a chip selection signal
57
and a read/write selection signal
56
are supplied from an external control circuit (e.g. the read channel LSI
102
) to the read/write switching circuit
34
. The chip selection signal
57
enables the drive circuit
15
and sets it in an operational state, and the read/write selection signal
56
indicates whether a read operation or a write operation is to be performed. In the present example, the signal
56
indicates that a write operation is to be performed. In response to such signals
56
and
57
, the switching circuit
34
outputs a read/write mode signal indicating that a write operation is to be performed.
The external control circuit also outputs a two bit head selection signal
51
and
52
to the head selection circuit
35
for selecting one of the four heads
3
to
6
. The circuit
35
inputs the signal
51
and
52
and determines that the magnetic head
3
has been selected to perform a read or write operation. As a result, the circuit
35
outputs an enable signal to enable the write driver
26
and read preamplifier
30
which are connected to the magnetic head
3
.
The write current generation circuit
36
inputs the read/write mode signal from the read/write switching circuit
34
, a predetermined write bias current, and a write data signal
53
. The predetermined write bias current is generated by connecting an external resistor
55
between the write current terminal
54
and ground. Since the read/write mode signal from the circuit
34
indicates a write mode, the generation circuit
36
outputs the predetermined write bias current based on the write data
53
to the write drivers
26
to
29
. Since the enable signal output from the head selection circuit
35
enables the write driver
26
, the write driver
26
drives the write head
3
a
with the write bias current output from the generation circuit
36
to write data to the magnetic disk
1
. For example, if a logic “1” is to be written to the disk
1
, the write driver causes the write bias current to travel in one direction through the write head
3
a
. On the other hand, if a logic “0” is to be written to the disk
1
, the write driver causes the write bias current to travel in the other direction through the write head
3
a.
When current is read from a disk (e.g. the disk
1
) via a particular read head (e.g. read head
3
b
), the chip selection signal
57
sets the drive circuit
15
in an operational state, and the read/write selection signal
56
indicates that a read operation is to be performed. As a result, the switching circuit
34
outputs a read/write mode signal indicating a read mode.
Also, the circuit
35
inputs the head selection signal
51
and
52
and determines that the magnetic head
3
has been selected to perform a read or write operation and enables the write driver
26
and read preamplifier
30
. As a result, the read preamplifier
30
inputs a predetermined read current and applies a read bias current to the read head
3
b
based on the predetermined read current so that the head
3
b
reads data from the disk
1
and supplies it to the preamplifier
30
. The predetermined read current is generated by connecting an external resistor
61
between the read current terminal
60
and ground.
Then, the preamplifier
30
amplifies the signal received from the head
3
b
and supplies the amplified signal to the postamplifier
23
. The read head
3
b
may be a magnetic-to-electrical resistor which changes resistance based on the magnetic field applied to the resistor. Thus, when a logic “0” on the disk passes by the head
3
b
, the head
3
b
has one resistance, and when a logic “1” on the disk passes by the head
3
b
, the head
3
b
has another resistance. Thus, the read bias current flowing through the head
3
b
changes depending on the read data, and thus, the value of the data can be determined based on the changing current. Since the read/write mode signal from the circuit
34
indicates a read mode, the postamplifier
23
amplifies the signal from the preamplifier
30
and outputs it as read data
58
and
59
.
The above example illustrates the operation of the drive circuit
15
when data is written to the disk
1
via the write head
3
a
and when data is read from the disk
1
via the read head
3
b
. Also, the circuit
15
operates in a similar manner when data is being written via the write heads
4
a
to
6
a
and when data is being read via the read heads
4
b
to
6
b.
Recently, increasing the storage capacity of hard disk drives has become extremely desirable. One method of increasing such capacity is to increase the frequency of the write data signal so that a larger amount of data can be stored in a fixed area of a magnetic disk. In other words, the speed at which data is written to or read from the disk is increased. The recording frequency can be raised by decreasing the inductance of the write head. However, when the inductance of the write head decreases, the level of stray inductance which will adversely affect the write operation also decreases. Specifically, the write head is unable to properly write data to the disk if the amount of stray inductance surrounding the write head exceeds 10% of the inductance of the write head itself. Therefore, by lowering the inductance of the head, the sensitivity of the head to stray inductance increases, and thus, the recording frequency of data cannot be in
Neal Regina Y.
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Drive circuits for a magnetic recording device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Drive circuits for a magnetic recording device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Drive circuits for a magnetic recording device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2438658