Pseudo-differential magnetic recording system and method incorporating a dummy read element and a dummy transmission line

A system including a first transmission line, a second transmission line, a first element, a second element and a differential amplifier. The first element is configured to read a storage media to generate a read signal, where the first element is connected to the first transmission line. The second element is configured to detect interference and generate an interference signal, where the second element is connected to the second transmission line. The differential amplifier includes a first input and a second input, where the first input of the differential amplifier is connected to a the first transmission line and receives the read signal, and where the second input of the differential amplifier is connected to the second transmission line and receives the interference signal.

FIELD

The present disclosure relates to magnetic recording systems with trace suspension assemblies.

BACKGROUND

FIG. 1shows a hard disk drive (HDD)10that includes a hard disk assembly (HDA)12and a HDD printed circuit board (PCB)14. The HDA12includes one or more platters16, which have magnetic surfaces that are used to store data magnetically. Data is stored in binary form as a magnetic field of either positive or negative polarity. The platters16are arranged in a stack. The platters16and/or the stack is rotated by one or more spindle motors (one spindle motor18is shown). One or more read/write heads (hereinafter, “heads”) read data from and write data on the magnetic surfaces of the platters16. A single head20is shown. Each of the heads includes a write element (e.g., an inductor) that generates a magnetic field and a read element (e.g., a magneto-resistive (MR) element), which senses the magnetic field on one of the platters16. The heads are mounted at a distal end of one or more actuator arms (a single actuator arm22is shown). An actuator, such as a voice coil motor (VCM)24, moves the actuator arm22relative to the platters16.

The HDA12includes a preamplifier device26. The preamplifier device26may include amplifiers for amplifying signals received from the heads. When reading data, generated magnetic fields induce low-level analog signals in the read elements of the head20. The amplifiers amplify the low-level analog signals and output amplified analog signals to a read/write (R/W) channel (hereinafter, “read-channel”) module28.

The HDD PCB14includes the read-channel module28, a hard disk controller (HDC) module30, a processor32, a spindle/VCM driver module34, volatile memory36, nonvolatile memory38, and an input/output (I/O) interface40. During write operations, the read-channel module28may encode the data to increase reliability by using error-correcting codes (ECC) such as run length limited (RLL) code, Reed-Solomon code, etc. The read-channel module28then transmits the encoded data to the preamplifier device26. During read operations, the read-channel module28receives analog signals from the preamplifier device26. The read-channel module28converts the analog signals into digital signals, which are decoded to recover the data previously stored on the platters16.

The HDC module30controls operation of the HDD10. For example, the HDC module30generates commands that control the speeds of the one or more spindle motors and the movement of the one or more actuator arms. The spindle/VCM driver module34implements the commands and generates control signals that control the speeds of the one or more spindle motors and the positioning of the one or more actuator arms. Additionally, the HDC module30communicates with an external device (not shown), such as a host adapter within a host device, via the I/O interface40. The HDC module30may receive data to be stored from the external device, and may transmit retrieved data to the external device.

The processor32processes data, including encoding, decoding, filtering, and/or formatting. Additionally, the processor32processes servo or positioning information to position the heads over the platters16during read/write operations. Servo, which is stored on the platters16, ensures that data is written to and read from correct locations on the platters16. In some implementations, a self-servo write (SSW) module42may write servo on the platters16using the heads prior to storing data on the HDD10.

The HDA12may include a two-dimensional magnetic recording (TDMR) system50and/or other system having a trace suspension assembly (TSA)52and multiple read elements. The TSA52refers to the one or more actuator arms and transmission lines (e.g., transmission lines54are shown) extending between the preamplifier device26and the heads. The transmission lines (sometimes referred to as traces) are suspended over the platters16via the one or more actuator arms. A TDMR system, such as the TDMR system50, uses multiple heads positioned adjacent each other to read a single track on a surface of a platter. Signals from the heads are processed to counteract, cancel and/or minimize noise (e.g., inter-track noise and backplane noise coupling) detected during the reading of the track. Inter-track noise can refer to magnetic field characteristics detected and associated with one or more tracks adjacent to the track being read. Backplane noise coupling can refer to noise coupling associated with parallel connected transmission lines, where each of the parallel connected transmission lines is connected to a common ground. Reducing noise improves signal-to-noise ratios for improved recovery of data stored on the tracks.

FIG. 2shows a magnetic recording system60that may be used in the HDA12ofFIG. 1. The magnetic recording system60may be a TDMR system and includes read elements62, transmission lines64, and a preamplifier device66. The preamplifier device66includes differential amplifiers68. Each of the read elements62is connected to a respective one of the differential amplifiers68via a respective one of the transmission lines64. The differential amplifiers68receive single-ended signals from the transmission lines64, convert the single-ended signals to differential output signals Out1-OutN, and output the differential output signals Out1-OutN, as shown. Gain of each of the differential amplifiers68may be adjusted to increase amplitudes of the differential output signals Out1-OutN and/or to improve corresponding signal-to-noise ratios.

As read cycle frequencies increase, noise picked-up by the read elements62can increase, which can negatively affect the signal-to-noise ratios. To minimize and/or cancel the noise, a fully differential magnetic recording system may be used instead of the magnetic recording system60. A fully differential magnetic recording system provides improved common mode noise rejection by providing differential signals from read elements to differential amplifiers. Common mode noise rejection refers to cancellation of noise common to both inputs of a differential amplifier.FIG. 3shows an example of a fully differential magnetic recording system70that may be used in the HDA12ofFIG. 1.

The magnetic recording system70includes read elements72, transmission lines74, and a preamplifier device76. The preamplifier device76includes differential amplifiers78. Each of the read elements72is connected to a respective one of the differential amplifiers78via a respective pair of the transmission lines74. The read elements72provide differential signals to inputs of the differential amplifiers78. Noise signals received at the inputs of each of the differential amplifiers78may be compared and cancelled by the corresponding one of the differential amplifiers78. The differential amplifiers78provide differential output signals Out1, Out2. Gain of each of the differential amplifiers78may be adjusted to increase amplitudes of the output signals Out1, Out2and/or to improve corresponding signal-to-noise ratios.

SUMMARY

A system is provided and includes a first transmission line, a second transmission line, a first element, a second element and a differential amplifier. The first element is configured to read a storage media to generate a read signal, where the first element is connected to the first transmission line. The second element is configured to detect interference and generate an interference signal, where the second element is connected to the second transmission line. The differential amplifier includes a first input and a second input, where the first input of the differential amplifier is connected to a the first transmission line and receives the read signal, and where the second input of the differential amplifier is connected to the second transmission line and receives the interference signal.

In other features, the second element is not configured to read data or information from a track. In other features, the system includes multiple transmission lines including the first transmission line and not the second transmission line. The read signal is a first read signal. The system further includes elements and differential amplifiers. The elements include the first element, where the elements are configured to read one or more tracks on the storage media to generate read signals. The read signals include the first read signal. Each of the elements is connected to a respective one of the transmission lines. The differential amplifier is a first differential amplifier. The differential amplifiers include the first differential amplifier, where the differential amplifiers are connected respectively to the plurality of elements via the transmission lines, and where the differential amplifiers include respective first inputs and respective second inputs. Each of the first inputs of the differential amplifiers is connected to a respective one of the transmission lines and receives a respective one of the read signals. Each of the second inputs of the differential amplifiers is connected to the second transmission line and receives the interference signal.

In other features, the differential amplifiers are configured to amplify differential input signals. Each of the differential input signals is based on one of the read signals and the interference signal.

In other features, the transmission lines include the first transmission line and a third transmission line. The elements include the first element and a third element. The differential amplifiers include the first differential amplifier and a second differential amplifier. The first element is connected between a ground reference and the first transmission line. The second element is connected between the ground reference and the second transmission line. The third element is connected between the ground reference and the third transmission line. The first transmission line is connected between the first element and the first input of the first differential amplifier. The second transmission line is connected between the second element and each of the second inputs of the differential amplifiers. The third transmission line is connected between the third element and the first input of the second differential amplifier.

In other features, the system includes a capacitance connected in series with the second transmission line and between the second transmission line and the second inputs of the differential amplifiers. In other features, the system includes a capacitance connected between the second transmission line and the second inputs of the differential amplifiers.

In other features, a system is provided that includes transmission lines, elements, a second element, and differential amplifiers. The elements are configured to read one or more tracks on a storage media to generate read signals, where each of the elements is connected to a respective one of the transmission lines. The second element is configured to detect interference and generate an interference signal, where the second element is connected to a dummy transmission line. The differential amplifiers are connected respectively to the elements via the transmission lines, where each of the differential amplifiers includes a first input and a second input, and where each of the first inputs of the differential amplifiers is connected to a respective one of the transmission lines and receives a respective one of the read signals. Each of the second inputs of the differential amplifiers is connected to the dummy transmission line and receives the interference signal.

In other features, a method is provided and includes: reading a track on a disk to generate a read signal via a first element, where the first element is connected to a first transmission line; detecting interference and generating an interference signal via a second element, where the second element is connected to a second transmission line; receiving the read signal at a first input of a differential amplifier; and receiving the interference signal at a second input of the differential amplifier. The first input of the differential amplifier is connected to the first transmission line. The second input of the differential amplifier is connected to the second transmission line. In other features, the transmission lines include the first transmission line and not the second transmission line. The track is a first track. The read signal is a first read signal. The differential amplifier is a first differential amplifier.

In other features, the method further includes reading one or more tracks on the disk to generate read signals via elements, where the read signals include the first read signal, where the elements include the first element, and where each of the elements is connected to a respective one of the transmission lines. The method further includes receiving the read signals respectively at differential amplifiers, where the differential amplifiers include the first differential amplifier and are connected respectively to the elements via the transmission lines. The differential amplifiers include respective first inputs and respective second inputs. The first inputs receive respectively the read signals. The method further includes receiving the interference signal at each of the second inputs of the differential amplifiers, where each of the second inputs is connected to the second transmission line.

DESCRIPTION

Although a fully differential magnetic recording system, as shown inFIG. 3, minimizes noise and improves signal-to-noise ratios, a corresponding actuator arm can be congested. This is because a fully differential magnetic recording system includes a pair of transmission lines for each read element and corresponding differential amplifier. The more read elements associated with an actuator arm the more transmission lines extending across the actuator arm. Thus, a large number of transmission lines can be extended across an actuator arm of a fully differential magnetic recording system.

The following disclosed implementations include pseudo-differential magnetic recording systems. These systems have fewer transmission lines than a fully differential magnetic recording system and provide noise reduction and/or cancellation similar to a magnetic recording system having a single transmission line per differential amplifier (e.g., the magnetic recording system ofFIG. 2).

FIG. 4shows a pseudo-differential magnetic recording system80that may be used in the HDA12ofFIG. 1. The pseudo-differential magnetic recording system80may be a TDMR system and includes read circuits82and a preamplifier device84. The read circuits82include read elements86and transmission lines88. The preamplifier device84includes differential amplifiers90. Each of the read elements86is connected to a respective one of the differential amplifiers90via a respective one of the transmission lines88. The read elements86include active read elements MR0-MRNand a dummy (or floating) read element MRD. An active read element refers to a read element that is used to read data and/or information from a track. A dummy read element refers to a read element that is not used to read data and/or information from a track, but rather is used for interference (including noise) cancellation purposes. The dummy read element MRDmay have a same resistance and/or impedance as each of the active read elements MR0-MRN. Each of the read elements MR0-MRNand MRDmay be connected between a ground reference92and a respective one of the transmission lines88.

The transmission lines88include transmission lines T0-TNand a dummy transmission line TD. A dummy circuit94includes the dummy read element MRDand the dummy transmission line TD. First ends96of the transmission lines T0-TNare connected respectively to the active read elements MR0-MRN. Second ends98of the transmission lines T0-TNare connected to respective first inputs100of the differential amplifiers90. A first end102of the dummy transmission line TDis connected to the dummy read element MRD. If the dummy transmission line TDis DC coupled, a second end104of the dummy transmission line TDis connected to second inputs106of the differential amplifiers90. The dummy transmission line TDmay have a same impedance as each of the transmission lines T0-TN. A collective impedance of the dummy read element MRDand the dummy transmission line TDmay be a same impedance as a collective impedance of each of the read elements MR0-MRNand a corresponding one of the transmission lines T0-TN. Impedances of the dummy circuit94as seen at each of the second inputs106may be the same and/or within a predetermined range of each other.

Impedances of each of the read circuits82as seen at each of the first inputs100may be matched such that (i) impedances seen at each of the first inputs100are a same impedance, and/or (ii) impedances seen at each of the first inputs100are within a predetermined range of each other. Impedances of each of the circuits82,94as seen at each of the inputs100,106may be matched such that (i) impedances seen at each of the first inputs100are a same impedance seen at each of the second inputs106, and/or (ii) impedances seen at each of the first inputs100are within a predetermined range of the impedances seen at each of the second inputs106.

The differential amplifiers90receive differential input signals from the transmission lines88, convert the differential input signals to differential output signals Out1-OutN, and output the differential output signals Out1-OutN, as shown. Each of the differential input signals is provided by the transmission line TDand a respective one of the transmission lines T0-Nto a respective one of the differential amplifiers90. Interference including noise common to both inputs of each of the differential amplifiers90may be cancelled by the differential amplifiers90to provide common mode noise rejection. Gain of each of the differential amplifiers68may be adjusted to increase amplitudes of the differential output signals Out1-OutN and/or to improve corresponding signal-to-noise ratios.

FIG. 5shows a pseudo-differential magnetic recording system120that may be used in the HDA12ofFIG. 1. The pseudo-differential magnetic recording system120may be a TDMR system and includes read circuits122and a preamplifier device124. The read circuits122include read elements126and transmission lines128. The preamplifier device124includes differential amplifiers130. Each of the read elements126is connected to a respective one of the differential amplifiers130via a respective one of the transmission lines128. The read elements126include active read elements MR0-MRNand a dummy (or floating) read element MRD. The dummy read element MRDmay have a same resistance and/or impedance as each of the active read elements MR0-MRN. Each of the read elements MR0-MRNand MRDmay be connected between a ground reference132and a respective one of the transmission lines128.

The transmission lines128include transmission lines T0-TNand a dummy transmission line TD. A dummy circuit134includes the dummy read element MRDand the dummy transmission line TD. First ends136of the transmission lines T0-TNare connected respectively to the read elements MR0-MRN. Second ends138of the transmission lines T0-TNare connected to respective first inputs140of the differential amplifiers130. A first end142of the dummy transmission line TDis connected to the read element MRD. A second end144of the dummy transmission line TDis connected to second inputs146of each of the differential amplifiers130. The dummy transmission line TDmay have a same impedance as each of the transmission lines T0-TN.

A collective impedance of the dummy read element MRDand the dummy transmission line TDmay be a same impedance as a collective impedance of each of the read elements MR0-MRNand a corresponding one of the transmission lines T0-TN. Impedances of each of the read circuits122as seen at each of the first inputs140may be matched such that (i) impedances seen at each of the first inputs140are a same impedance, and/or (ii) impedances seen at each of the first inputs140are within a predetermined range of each other. Impedances of the dummy circuit134as seen at each of the second inputs146of the differential amplifiers130may be the same and/or within a predetermined range of each other.

The differential amplifiers130receive differential input signals from the transmission lines128, convert the differential input signals to differential output signals Out1-OutN, and output the differential output signals Out1-OutN, as shown. Each of the differential input signals is provided by the transmission line TDand a respective one of the transmission lines T0-Nto a respective one of the differential amplifiers130. Interference including noise common to both inputs of each of the differential amplifiers130may be cancelled by the differential amplifiers130to provide common mode noise rejection. Gain of each of the differential amplifiers130may be adjusted to increase amplitudes of the differential output signals Out1-OutN and/or to improve corresponding signal-to-noise ratios.

The dummy transmission line TDmay be DC coupled or AC coupled. The DC coupling and the AC coupling may be provided by circuit elements internal to and/or external from the preamplifier device124and/or the differential amplifiers130. In the example shown, the DC coupling and the AC coupling is provided by circuit elements external to the preamplifier device124and the differential amplifiers130. If the dummy transmission line TDis DC coupled, the second end144of the dummy transmission line TDis connected to the second inputs146of the differential amplifiers130. If the dummy transmission line TDis AC coupled, a capacitance CACmay be connected between the second end144of the dummy transmission line TDand each of the second inputs146of the differential amplifiers130.

FIG. 6shows a pseudo-differential magnetic recording system150that may be used in the HDA12ofFIG. 1. The pseudo-differential magnetic recording system150may be a TDMR system and includes read circuits152and a preamplifier device154. The read circuits152include read elements156and transmission lines158. The preamplifier device154includes differential amplifiers160. Each of the read elements156is connected to a respective one of the differential amplifiers160via a respective one of the transmission lines158. The read elements156include active read elements MR0-MRNand a dummy (or floating) read element MRD. The read element MRDmay have a same resistance and/or impedance as each of the active read elements MR0-MRN. Each of the read elements MR0-MRNand MRDmay be connected between a ground reference162and a respective one of the transmission lines158.

The transmission lines158include transmission lines T0-TNand a dummy transmission line TD. A dummy circuit164includes the dummy read element MRDand the dummy transmission line TD. First ends166of the transmission lines T0-TNare connected respectively to the read elements MR0-MRN. Second ends168of the transmission lines T0-TNare connected to respective first inputs170of the differential amplifiers160. A first end172of the dummy transmission line TDis connected to the read element MRD. A second end174of the dummy transmission line TDis connected to second inputs176of the differential amplifiers160.

The dummy transmission line TDmay have a same impedance as each of the transmission lines T0-TN. A collective impedance of the dummy read element MRDand the dummy transmission line TDmay be a same impedance as a collective impedance of each of the read elements MR0-MRNand a corresponding one of the transmission lines T0-TN. Impedances of each of the read circuits152as seen at each of the first inputs170may be matched such that (i) impedances seen at each of the first inputs170are a same impedance, and/or (ii) impedances seen at each of the first inputs170are within a predetermined range of each other. Impedances of the dummy circuit164as seen at each of the second inputs176may be the same.

The differential amplifiers160receive differential input signals from the transmission lines158, convert the differential input signals to differential output signals Out1-OutN, and output the differential output signals Out1-OutN, as shown. Each of the differential input signals is provided by the transmission line TDand a respective one of the transmission lines T0-Nto a respective one of the differential amplifiers160. Interference including noise common to both inputs of each of the differential amplifiers160may be cancelled by the differential amplifiers160to provide common mode noise rejection. Gain of each of the differential amplifiers160may be adjusted to increase amplitudes of the differential output signals Out1-OutN and/or to improve corresponding signal-to-noise ratios.

The dummy transmission line TDmay be DC coupled or AC coupled. The DC coupling and the AC coupling may be provided by circuit elements internal to or external from the preamplifier device154and/or the differential amplifiers160. In the example shown, the DC coupling and the AC coupling is provided by circuit elements external to the preamplifier device154and the differential amplifiers160. If the dummy transmission line TDis DC coupled, the second end174of the dummy transmission line TDis connected to the second inputs176of the differential amplifiers160. If the dummy transmission line TDis AC coupled, each of capacitances CACmay be connected between the second end174of the dummy transmission line TDand a respective one of the second inputs176of the differential amplifiers160.

The magnetic recording systems (e.g., one of the magnetic recording systems80,120,150) disclosed herein may be operated using numerous methods, an example method is illustrated inFIG. 7.FIG. 7illustrates a magnetic recording method in accordance with the present disclosure. Although the following tasks are primarily described with respect to the implementations of FIGS.1and4-6, the tasks may be easily modified to apply to other implementations of the present disclosure. The tasks may be iteratively performed.

The magnetic recording method may begin at200. At202, read signals and corresponding voltages are generated via active read elements (e.g., read elements MR0-MRN). Each of the active read elements has a respective transmission line (e.g., one of the transmission lines T0-TN) and a respective differential amplifier (one of the differential amplifiers90,130,160). The active read signals may include data and/or information read from a track and may also include interference including noise picked-up by the active read elements.

At203, a dummy signal (referred to also as an interference signal) is generated via a dummy read element (e.g., the dummy read element MRD). The dummy signal may not include data and/or information read from a track, but rather may include interference including noise picked-up by the dummy read element MRD. Task203is performed while task202is performed.

At204, the read signals are provided from the active read elements to respective first inputs of the differential amplifiers via respective transmission lines. At205, the dummy signal is provided from the dummy read element to the second inputs of the differential amplifiers via the dummy transmission line. The second inputs may be DC coupled or AC coupled as described above. Task205is performed while task204is performed.

At206, differential input signals are received at input terminals of the differential amplifiers via the transmission lines. Each of the differential input signals is provided by an output of a respective one of the transmission lines and an output of the dummy transmission line. Each of the differential input signals is thus based on a respective one of the read signals and the dummy signal. The dummy signal is received at the second inputs of the differential amplifiers while the read signals are received at the first input of the differential amplifiers. At208, the differential input signals are converted as described above to generate differential output voltages. The differential input signals are amplified via the differential amplifiers to generate the differential output signals. Interference including noise contained in the read signals and the dummy signal is cancelled and/or minimized by the differential amplifiers to provide the differential output signals with minimal noise. Interference including noise that is common to both inputs of each of the differential amplifiers is cancelled.

At210, the differential output signals are received at respective read/write channels of a read/write channel module (e.g., read-channel module28). At212, the read/write channel module may include an analog-to-digital (A/D) converter and convert the differential output voltages, which are provided as analog signals, into digital signals. The read/write channel module may decode the digital signals to recover original data. This may include error correction code (ECC) decoding and/or run-length-limited (RLL) decoding.

At214, a HDC module (e.g., the HDC module30) stores the data in memory (e.g., one of the memories36,38) and/or provides the data to a host via an interface (e.g., the interface40). The method may end at216.

The above-described tasks are meant to be illustrative examples; the tasks may be performed sequentially, synchronously, simultaneously, continuously, during overlapping time periods or in a different order depending upon the application. Also, any of the tasks may not be performed or skipped depending on the implementation and/or sequence of events.

In the foregoing description, various terms are used to describe the physical relationship between circuit elements. When a first element is referred to as being “engaged to”, “connected to”, or “coupled to” a second element, the first element may be directly engaged, connected, disposed, applied, or coupled to the second element, or intervening elements may be present. In contrast, when an element is referred to as being “directly engaged to”, “directly connected to”, or “directly coupled to” another element, there may be no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.).

The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure.

The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared processor encompasses a single processor that executes some or all code from multiple modules. The term group processor encompasses a processor that, in combination with additional processors, executes some or all code from one or more modules. The term shared memory encompasses a single memory that stores some or all code from multiple modules. The term group memory encompasses a memory that, in combination with additional memories, stores some or all code from one or more modules. The term memory is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium include nonvolatile memory (such as flash memory), volatile memory (such as static random access memory and dynamic random access memory), magnetic storage (such as magnetic tape or hard disk drive), and optical storage.

The apparatuses and methods described in this application may be partially or fully implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include and/or rely on stored data.