U.S. patent application number 14/090873 was filed with the patent office on 2015-05-28 for disk drive slider with sense amplifier for coupling to a preamp through a supply/bias line and a read signal line.
This patent application is currently assigned to Western Digital Technologies, Inc.. The applicant listed for this patent is Western Digital Technologies, Inc.. Invention is credited to DENNIS W. HOGG.
Application Number | 20150146319 14/090873 |
Document ID | / |
Family ID | 53182484 |
Filed Date | 2015-05-28 |
United States Patent
Application |
20150146319 |
Kind Code |
A1 |
HOGG; DENNIS W. |
May 28, 2015 |
DISK DRIVE SLIDER WITH SENSE AMPLIFIER FOR COUPLING TO A PREAMP
THROUGH A SUPPLY/BIAS LINE AND A READ SIGNAL LINE
Abstract
A disk drive slider is disclosed comprising a first read element
for generating a first read signal, and a first sense amplifier
comprising a first input terminal coupled to the first read
element, a first output terminal coupled to a first output line,
and a first supply terminal coupled to a supply line. The first
sense amplifier is for amplifying the first read signal to generate
a first amplified read signal, the first output line is for
transmitting the first amplified read signal to a preamp, and the
supply line is for coupling to the preamp in order to supply power
to the first sense amplifier and supply a first bias to the first
read element.
Inventors: |
HOGG; DENNIS W.; (LAGUNA
HILLS, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Western Digital Technologies, Inc. |
Irvine |
CA |
US |
|
|
Assignee: |
Western Digital Technologies,
Inc.
Irvine
CA
|
Family ID: |
53182484 |
Appl. No.: |
14/090873 |
Filed: |
November 26, 2013 |
Current U.S.
Class: |
360/46 |
Current CPC
Class: |
G11B 5/455 20130101;
G11B 5/09 20130101; G11B 5/02 20130101; G11B 20/10027 20130101;
G11B 20/10018 20130101; G11B 5/012 20130101; G11B 5/4853 20130101;
G11B 5/58 20130101; G11B 5/5526 20130101 |
Class at
Publication: |
360/46 |
International
Class: |
G11B 20/10 20060101
G11B020/10 |
Claims
1. A disk drive slider comprising: a first read element for
generating a first read signal; and a first sense amplifier
comprising a first input terminal coupled to the first read
element, a first output terminal coupled to a first output line,
and a first supply terminal coupled to a supply line, wherein: the
first sense amplifier is for amplifying the first read signal to
generate a first amplified read signal; the first output line is
for transmitting the first amplified read signal to a preamp; and
the supply line is for coupling to the preamp in order to supply
power to the first sense amplifier and supply a first bias to the
first read element.
2. The disk drive slider as recited in claim 1, further comprising:
a second read element for generating a second read signal; and a
second sense amplifier comprising a second input terminal coupled
to the second read element, a second output terminal coupled to a
second output line, and a second supply terminal coupled to the
supply line, wherein: the second sense amplifier is for amplifying
the second read signal to generate a second amplified read signal;
the second output line is for transmitting the second amplified
read signal to the preamp; and the supply line is for coupling to
the preamp in order to supply power to the second sense amplifier
and supply a second bias to the second read element.
3. The disk drive slider as recited in claim 1, wherein the first
sense amplifier is for generating the first amplified read signal
as a single ended signal.
4. A disk drive preamp comprising: a supply line for coupling to a
first supply terminal of a first sense amplifier of a slider; and a
first input line for coupling to a first output terminal of the
first sense amplifier, wherein: the first sense amplifier is for
amplifying a first read signal generated by a first read element of
the slider to generate a first amplified read signal; the first
input line is for receiving the first amplified read signal; and
the supply line is for supplying power to the first sense amplifier
and for supplying a first bias to the first read element.
5. The disk drive preamp as recited in claim 4, further comprising
a second input line for coupling to a second output terminal of a
second sense amplifier, wherein: the second sense amplifier is for
amplifying a second read signal generated by a second read element
of the slider to generate a second amplified read signal; the
second input line is for receiving the second amplified read
signal; and the supply line is for supplying power to the second
sense amplifier and for supplying a second bias to the second read
element.
6. The disk drive preamp as recited in claim 4, wherein the first
input line is for receiving the first amplified read signal as a
single ended signal.
7. The disk drive preamp as recited in claim 4, further comprising
a first current source coupled to the first input line for
controlling an output impedance of the first sense amplifier.
8. The disk drive preamp as recited in claim 5, further comprising:
a first current source coupled to the first input line for
controlling a first output impedance of the first sense amplifier;
and a second current source coupled to the second input line for
controlling a second output impedance of the second sense
amplifier.
9. A method of operating a disk drive preamp, the disk drive preamp
comprising: a supply line for coupling to a first supply terminal
of a first sense amplifier of a slider; and a first input line for
coupling to a first output terminal of the first sense amplifier,
wherein: the first sense amplifier is for amplifying a first read
signal generated by a first read element of the slider to generate
a first amplified read signal; the first input line is for
receiving the first amplified read signal; and the supply line is
for supplying power to the first sense amplifier and for supplying
a first bias to the first read element, wherein the method
comprises adjusting a current source coupled to the first input
line to adjust an output impedance of the first sense
amplifier.
10. A disk drive comprising: a disk; a slider actuated over the
disk, the slider comprising a first read element, a first sense
amplifier, a second read element, and a second sense amplifier; a
preamp comprising: a supply line for coupling to a first supply
terminal of the first sense amplifier and for coupling to a second
supply terminal of the second sense amplifier; and a first input
line for coupling to a first output terminal of the first sense
amplifier, and a second input line for coupling to a second output
terminal of the second sense amplifier, wherein: the first sense
amplifier is for amplifying a first read signal generated by the
first read element to generate a first amplified read signal; the
first input line is for receiving the first amplified read signal;
the second sense amplifier is for amplifying a second read signal
generated by the second read element to generate a second amplified
read signal; the second input line is for receiving the second
amplified read signal; and the supply line is for supplying power
to the first and second sense amplifier and for supplying an
operating bias to the first and second read element, and control
circuitry configured to: calibrate a first bias supplied to the
first read element; calibrate a second bias supplied to the second
read element; and generate the operating bias based on the first
bias and the second bias.
11. A method of operating a disk drive, the disk drive comprising a
preamp comprising: a supply line for coupling to a first supply
terminal of a first sense amplifier of a slider and for coupling to
a second supply terminal of a second sense amplifier of the slider;
and a first input line for coupling to a first output terminal of
the first sense amplifier, and a second input line for coupling to
a second output terminal of the second sense amplifier, wherein:
the first sense amplifier is for amplifying a first read signal
generated by a first read element of the slider to generate a first
amplified read signal; the first input line is for receiving the
first amplified read signal; the second sense amplifier is for
amplifying a second read signal generated by a second read element
of the slider to generate a second amplified read signal; the
second input line is for receiving the second amplified read
signal; and the supply line is for supplying power to the first and
second sense amplifier and for supplying an operating bias to the
first and second read element, wherein the method comprises:
calibrating a first bias supplied to the first read element;
calibrating a second bias supplied to the second read element; and
generating the operating bias based on the first bias and the
second bias.
12. A disk drive comprising: a disk a slider actuated over the
disk, the slider comprising a first read element and a second read
element; and control circuitry configured to: calibrate a first
bias supplied to the first read element; calibrate a second bias
supplied to the second read element; generate an operating bias
based on the first bias and the second bias, and apply the
operating bias to the first read element and the second read
element when reading data from the disk.
13. The disk drive as recited in claim 12, wherein the control
circuitry is configured to generate the operating bias by averaging
the first bias and the second bias.
14. A method of operating a disk drive comprising: calibrating a
first bias supplied to a first read element; calibrating a second
bias supplied to a second read element; generating an operating
bias based on the first bias and the second bias; and applying the
operating bias to the first read element and the second read
element when reading data from a disk.
15. The method as recited in claim 14, further comprising
generating the operating bias by averaging the first bias and the
second bias.
Description
BACKGROUND
[0001] Disk drives comprise a disk and a head connected to a distal
end of an actuator arm which is rotated about a pivot by a voice
coil motor (VCM) to position the head radially over the disk. The
disk comprises a plurality of radially spaced, concentric tracks
for recording user data sectors and embedded servo sectors. The
embedded servo sectors comprise head positioning information (e.g.,
a track address) which is read by the head and processed by a servo
controller to control the actuator arm as it seeks from track to
track.
[0002] A number of heads are typically fabricated on a substrate of
a wafer (e.g., an aluminum titanium carbide (ALTiC) wafer) which is
then sliced to form sliders. Each slider is coupled to one of the
actuator arms through a suspension that biases the slider toward
the disk surface. The slider comprises an air-bearing surface (ABS)
wherein as the disk rotates, an air-bearing is formed between the
slider and the disk that counteracts the bias force of the
suspension. Accordingly, the head essentially flies just above the
disk surface during write/read operations. Data is typically
written to the disk by modulating a write current in an inductive
coil of the head to record magnetic transitions onto the disk
surface in a process referred to as saturation recording. During
readback, the magnetic transitions are sensed by a read element
(e.g., a magnetoresistive element) of the head and the resulting
read signal demodulated by a suitable read channel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] FIG. 1A shows a disk drive according to an embodiment
comprising a head fabricated on a slider that is actuated over a
disk.
[0004] FIG. 1B shows an interconnect for connecting the first read
element to a preamp through a first sense amplifier of the slider
according to an embodiment.
[0005] FIG. 1C shows an embodiment wherein the first sense
amplifier comprises a first input terminal coupled to the first
read element, a first output terminal coupled to a first output
line, and a first supply terminal coupled to a first input
line.
[0006] FIG. 2 shows an embodiment of the first sense amplifier for
amplifying a first read signal generated by the first read
element.
[0007] FIG. 3 shows an embodiment wherein the slider comprises
multiple read elements and a separate sense amplifier for
amplifying each read signal generated by each read element.
DETAILED DESCRIPTION
[0008] FIG. 1A shows a disk drive comprising a head 2 actuated over
a disk 4 according to an embodiment, wherein the head 2 is
fabricated on a disk drive slider 6 (FIG. 1C) comprising a first
read element 8.sub.1 for generating a first read signal 10.sub.1,
and a first sense amplifier 12.sub.1. The first sense amplifier
12.sub.1 comprises a first input terminal coupled to the first read
element 8.sub.1, a first output terminal coupled to a first output
line 14.sub.1, and a first supply terminal coupled to a supply line
16. The first sense amplifier 12.sub.1 is for amplifying the first
read signal 10.sub.1 to generate a first amplified read signal, the
first output line 14.sub.1 is for transmitting the first amplified
read signal to a preamp 18, and the supply line 16 is for coupling
to the preamp 18 in order to supply power to the first sense
amplifier 12.sub.1 and supply a first bias to the first read
element 8.sub.1.
[0009] In the embodiment of FIG. 1A, the preamp 18 is mounted on
the side of an actuator arm 20 that is rotated about a pivot by a
voice coil motor (VCM) 22. In one embodiment, the preamp 18 is
coupled to the slider 6 through a suitable interconnect 24 an
example of which is shown in FIG. 1B. In one embodiment, the
interconnect 24 comprises a suitable flex circuit comprising any
suitable number of transmission lines, including the first output
line 14.sub.1 and the supply line 16. In one embodiment, the first
sense amplifier 12.sub.1 of FIG. 1C provides an initial
amplification of the first read signal 10.sub.1 so as to reduce the
effective distortions of the interconnect 24. That is, the first
sense amplifier 12.sub.1 may allow a gain of the preamp 18 to be
reduced so as to reduce the noise amplification of the preamp 18.
In addition, the first sense amplifier 12.sub.1 may be fabricated
so that it's output impedance better matches the impedance of the
interconnect 24 transmission line and the preamp 18 as compared to
the impedance of the first read element 8.sub.1.
[0010] FIG. 1C illustrates another embodiment as comprising a disk
drive preamp 18 comprising a supply line 16 for coupling to a first
supply terminal of a first sense amplifier 12.sub.1 of a slider 6,
and a first input line 14.sub.1 for coupling to a first output
terminal of the first sense amplifier 12.sub.1. The first sense
amplifier 12.sub.1 is for amplifying a first read signal generated
by a first read element 8.sub.1 of the slider 6 to generate a first
amplified read signal. The first input line 14.sub.1 is for
receiving the first amplified read signal, and the supply line 16
is for supplying power to the first sense amplifier 12.sub.1 and
for supplying a first bias to the first read element 8.sub.1.
[0011] The preamp 18 receives the amplified read signal from the
first sense amplifier 12.sub.1 over line 14.sub.1 and further
amplifies the read signal to generate an amplified read signal
transmitted to control circuitry 26 over line 28 (FIG. 1A). The
control circuitry 26 may process the amplified read signal in order
to demodulate user data recorded on the disk 4 as well as servo
data, such as servo data recorded in concentric servo sectors. The
control circuitry 26 processes the servo data in order to generate
an actuator control signal, such as a VCM control signal 30 applied
to the VCM 22, in order to actuate the head 2 over the disk 4.
[0012] FIG. 2 shows an embodiment of the first sense amplifier
12.sub.1 as an integrated circuit that may be fabricated with the
slider 6 or fabricated separate from the slider 6 and then adhered
to the slider 6. FIG. 2 shows a particular circuit configuration
for implementing an amplifier; however, other embodiments may
employ any suitable amplifier circuit configuration. In addition,
the circuit components shown in FIG. 2 (resistors, transistors,
capacitors, etc.) may take on any suitable values, and in one
embodiment, the values may depend on the amplitude of the supply
voltage applied to the first sense amplifier 12.sub.1 over the
supply line 16 as well as the desired amplitude range of the
amplified read signal applied to the first output line
14.sub.1.
[0013] In the embodiment of FIG. 2, the first sense amplifier
12.sub.1 generates the first amplified read signal as a single
ended signal as compared to a differential signal. That is, the
first amplified read signal is generated relative to ground using a
single polarity supply voltage. In an embodiment described below,
generating the amplified read signal as a single ended signal
enables a multiple read element head wherein the read signal
generated by each read element is transmitted over a single
transmission line to the preamp 18.
[0014] In the embodiment of FIG. 2, the preamp 18 comprises a
suitable voltage source 32 for generating a supply voltage applied
to the supply line 16. The supply voltage provides power to the
first sense amplifier 12.sub.1 as well biases the first read
element 8.sub.1. The preamp 18 in the embodiment of FIG. 2 also
comprises a first current source 34 coupled to the first output
line 14.sub.1 of the first sense amplifier 12.sub.1. In one
embodiment, the first current source 34 is configured in order to
control an output impedance of the first sense amplifier 12.sub.1.
For example, the first current source 34 may be configured to
better match the output impedance of the first sense amplifier
12.sub.1 to the transmission line as well as to the input impedance
of the preamp 18.
[0015] FIG. 3 shows an embodiment wherein the slider 6 comprises
multiple read elements 8.sub.1-8.sub.N, including a second read
element 8.sub.2 for generating a second read signal, and a second
sense amplifier 12.sub.2 comprising a second input terminal coupled
to the second read element 8.sub.2, a second output terminal
coupled to a second output line 14.sub.2, and a second supply
terminal coupled to the supply line 16. The second sense amplifier
12.sub.2 is for amplifying the second read signal to generate a
second amplified read signal. The second output line 14.sub.2 is
for transmitting the second amplified read signal to the preamp 18.
The supply line 16 is for coupling to the preamp 18 in order to
supply power to the second sense amplifier 12.sub.2 and supply a
second bias to the second read element 8.sub.2.
[0016] The embodiment of FIG. 3 reduces the number of transmission
lines in the flex circuit of the interconnect 24 (FIG. 1 B) by
using the supply line 16 to supply power and bias all of the read
elements 8.sub.1-8.sub.N of the slider 6. When the amplified read
signals are generated as single ended signals such as shown in the
embodiment of FIG. 2, the flex circuit of the interconnect 24 may
comprise as few as N+1 transmission lines as compared to 4N
transmission lines if each read element 8.sub.1-8.sub.N were
powered and biased using separate lines, and if each amplified read
signal were generated as a differential signal.
[0017] Any suitable read element may be employed in the
embodiments, such as a magnetoresistive (MR) read element having a
resistance that varies relative to the magnetic field emanating
from the surface of the disk. In one embodiment, the read element
is biased (e.g., using a voltage or current applied over the supply
line 16) so as to optimize the sensitivity of the read element. In
an embodiment where the head 2 comprises multiple read elements
8.sub.1-8.sub.N such as shown in the embodiment of FIG. 3, the
control circuitry 26 (FIG. 1A) may execute a calibration procedure
to determine an optimal bias setting for each read element. The
control circuitry 26 may then configure the preamp 18 to bias the
read elements 8.sub.1-8.sub.N based on the optimal bias setting
calibrated for each read element 8.sub.1-8.sub.N. For example, the
control circuitry 26 may configure the preamp 18 to apply an
operating bias to at least two of the read elements 8.sub.1-8.sub.N
over the supply line 16, wherein the operating bias may be
generated as the average (or other suitable statistic) of the
optimal bias settings calibrated for each read element. In this
manner, at least two of the read elements may operate in parallel,
for example, to simultaneously read multiple data tracks, or to
read a single data track using multiple read elements to improve
the signal-to-noise ratio (SNR) by combining the resulting read
signals.
[0018] In one embodiment the control circuitry 26 of FIG. 1A may
comprise a suitable microprocessor executing instructions, the
instructions being operable to cause the microprocessor to perform
the embodiments described herein, such as executing the calibration
procedure to configure the bias setting for the read elements as
well as configure the preamp 18 during normal access operations.
The instructions may be stored in any computer-readable medium. In
one embodiment, they may be stored on a non-volatile semiconductor
memory external to the microprocessor, or integrated with the
microprocessor in a SOC. In another embodiment, the instructions
are stored on the disk and read into a volatile semiconductor
memory when the disk drive is powered on. In yet another
embodiment, the control circuitry 26 comprises suitable logic
circuitry, such as state machine circuitry.
* * * * *