Dynamic magnetic information storage or retrieval – General recording or reproducing – Specifics of the amplifier
Reexamination Certificate
2000-04-24
2003-08-05
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Specifics of the amplifier
C360S125330
Reexamination Certificate
active
06603623
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to write driver circuits for magnetic recording. More particularly, the present invention relates to write driver circuits for high data rate magnetic recording and techniques for fabricating such write driver circuits.
2. Description of the Related Art
FIG. 1
shows a high RPM disk drive
10
having a magnetic read/write head (or a recording slider) that is positioned over a selected track on a magnetic disk
11
for recording data using a servo system. The stage servo system includes a voice-coil motor (VCM)
13
for coarse positioning a read/write head suspension
12
and may include a microactuator, or micropositioner, for fine positioning the read/write head over the selected track.
FIG. 2
shows an enlarged exploded view of the read/write head end of suspension
12
in the case when a microactuator is also being used. An electrostatic rotary microactuator
14
is attached to a gimbal structure
15
on suspension
12
, and a slider
16
is attached to the microactuator. A read/write head
17
is fabricated as part of slider
16
.
For high data rate magnetic recording, the write path of a recording channel front-end requires a wide bandwidth and short waveform rise and fall times in order to accurately transfer high-frequency write data patterns to a magnetic medium, such as a disk. The write signal includes abrupt switching, that is, polarity reversals of the signal, that represent the information that is to-be-recorded. The abrupt switching generates high-frequency harmonics that must be transferred from the write driver to the magnetic write transducer (write head) in order that the write signal is accurately transferred onto the magnetic medium.
Conventional write drivers have a high output impedance, essentially forming a current source for the write current needed to drive an inductive write head. The output impedance is much greater than the head input impedance.
FIG. 3
shows a conventional write driver circuit
30
that is connected directly to the (bonding) terminals of a magnetic write transducer (write head)
32
through a suspension interconnect
31
. Write driver circuit
30
is configured as a current commutating write-driver circuit and includes two switches S and two switches {overscore (S)} that are connected in an H configuration. An obstacle in transferring the write data output signal from write driver circuit
30
to write head
32
is in the propagation of the write signal along interconnect
31
between write driver circuit
30
and the write head
32
.
The invention described below improves the propagation of the write signal along an interconnect between a write driver circuit and a write head, while maintaining the signal integrity, i.e., the signal properties essential for high data rate writing.
SUMMARY OF THE INVENTION
The present invention provides a technique for improving propagation of the write signal along an interconnect between a write driver circuit and a write head. The advantages of the present invention are provided by a method for forming a termination for a magnetic write head in which a magnetic write coil has an inner turn and an outer turn that are formed on a wafer. A bottom capacitor plate for a capacitor is formed on the wafer using a liftoff process or subtraction patterning using ion milling. A resistor having a first terminal and a second terminal is also formed on the wafer using a liftoff process or ion milling. A dielectric layer is formed over the bottom capacitor plate for the capacitor using, for example, a liftoff process. A top capacitor plate is formed on the dielectric layer using a liftoff process or ion milling. An overpass lead is formed between the inner turn of the coil and one of the bottom capacitor plate and the top capacitor plate. The first terminal of the resistor is connected to the capacitor plate that is not connected to the inner turn of the write coil. The second terminal of the resistor is connected to the outer turn of the write coil. An impedance formed by the write coil, the capacitor and the resistor substantially equals a characteristic impedance Z
0
of an interconnect circuit that will be connected to the write coil.
According to the invention, the capacitor and the resistor form a load termination network that is connected in parallel across the write coil. Further, the write coil has an inductance L
h
and a resistance R
h
, and the load termination network includes a first resistance R, a second resistance R
ex
and a capacitance C. The characteristic impedance Z
0
of the interconnect circuit, the inductance L
h
and the resistance R
h
of the coil, and the first resistance R, the second resistance R
ex
and the capacitance C of the load terminated network are related by
Z
0
=R=R
ex
+R
h
={square root over (L
h
/C
)}.
The present invention also provides a magnetic head that includes a substrate, a write coil formed on the substrate, and a load termination network for the coil formed on the substrate. The load termination circuit includes at least one of a capacitor and a resistor. Preferably, the load termination network includes a capacitor and a resistor that form a load termination network that is connected in parallel across the write coil so that an impedance formed by the write coil, the capacitor and the resistor substantially equals a characteristic impedance Z
0
of an interconnect circuit that will be connected to the write coil.
According to another aspect of the present invention, a disk drive includes a write driver output stage, an interconnect circuit and a magnetic head. The write driver output stage has an output. The interconnect circuit has an input, an output and a characteristic impedance Z
0
. The input of the interconnect circuit is coupled to the write signal output of the write driver output stage. The magnetic head has an input that is coupled to the output of the interconnect circuit. The magnetic head includes a substrate, a write coil formed on the substrate, and a load termination network for the coil formed on the substrate. The load termination circuit includes at least one of a capacitor and a resistor. Preferably, the load termination network includes a capacitor and a resistor that form a load termination network that is connected in parallel across the write coil so that an impedance formed by the write coil, the capacitor and the resistor substantially equals the characteristic impedance Z
0
of the interconnect circuit.
REFERENCES:
patent: 5121273 (1992-06-01), Slezak
patent: 5440434 (1995-08-01), Kanegae
patent: 5491597 (1996-02-01), Bennin et al.
patent: 5608591 (1997-03-01), Klaassen
patent: 5777829 (1998-07-01), Voldman et al.
patent: 5978181 (1999-11-01), Niijima et al.
patent: 6331919 (2001-12-01), Klaassen et al.
Fontana, Jr. Robert E.
Kasiraj Prakash
Klaassen Klaassen Berend
Williams Mason Lamar
Curtin, Esq. Joseph P.
Hudspeth David
Kapadia Varsha A.
Tran, Esq. Khanh Q.
LandOfFree
Inductive magnetic recording head with impedance matching... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Inductive magnetic recording head with impedance matching..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Inductive magnetic recording head with impedance matching... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3082289