Abstract: To calibrate the VGA of a read head, test signals from a DAC are input to the VGA and the output of the VGA is observed, with the gain of the VGA being adjusted as appropriate. So that the DAC need not be made with tight tolerances, a DC signal can be fed into the DAC prior to VGA calibration, and an auxiliary ADC is used to receive the output of the DAC and to determine, for a given DC input, what the signal produced by the DAC actually is. In this way, during subsequent VGA calibration the test signal from the DAC is known not by virtue of the DAC having a tight manufacturing tolerance but by virtue of the actual measurements of its outputs for given register inputs.

Abstract: A high-speed, wide bandwidth data detection circuit includes a phase detection module, a data detection module, a loop filter, and a voltage controlled oscillator. The phase detection module is operably coupled to produce a controlled current based on a current mode mathematical manipulation of differences between an incoming data stream and a recovered clock. The phase detection module performs the current mode mathematical manipulations and produces the controlled current in the current domain. The data detection module is operably coupled to produce the detected data based on the incoming data stream and the recovered clock. The loop filter is operably coupled to convert the controlled current into a controlled voltage. The voltage controlled oscillator is operably coupled to convert the control voltage into the recovered clock.

Abstract: The invention is directed to a magnetic head driving circuit and a magnetic disk device which achieve a low flying-height with thermal protrusion and thus a reliable write operation on the magnetic disk. The write circuit 3 receives the write data signal Sw inputted therein, and generates and outputs the write voltages Wx, Wy based upon the inputted signal. The write voltages Wx, Wy are composed of a preamble portion T1, a sink mark T2 and a user data portion T3 in each sector for magnetic recording. In the write voltage, the frequency f2 of the signal in the preamble portion T1 is higher than half the frequency f1 of the signal in the user data portion T3.

Abstract: A method and apparatus for optimizing write properties of a magnetic head capable of performing read/write functions on a medium including defining the magnetic head as a normal head, a low temperature weak write (WW) head, or a high temperature WW head, and optimizing the write properties using optimal over shoot control (OSC) and write current (WC) according to the defined kind of magnetic head. Accordingly, the magnetic head in a hard disk drive (HDD) can be defined as the normal head, the low temperature WW head, or the high temperature WW head. Since the method uses the optimal OSC and WC values, according to the defined kind of magnetic head, in consideration of writability of the magnetic head and environmental temperature, low temperature or high temperature WW problems are avoided.

Abstract: In an apparatus for recording and regenerating data, a pass metric is calculated based on a likelihood converted from a previous calculation result iteratively until all pass metrics of the same data recorded many times on a recording medium are calculated, and then data recorded on the recording medium is decoded.

Abstract: A write driver circuit (38) uses a matching resistors (R0, R1) to match the impedance of the head (32) disposed between output nodes (OUTP, OUTN). Control circuitry (Q4, Q5, Q6, Q7, R2, R4, R6 and R7) maintains the voltage at reference voltage nodes (VREFP, REFN) at essentially the same voltage as its corresponding output node. The matching resistor is disposed between the reference voltage node and the output node along with a driver (40a, 40b), which may be implemented as an AB driver. Since the voltage between the reference node and the output node is generally zero, very little current is shunted by the matching resistors, and thus, there is very little power wasted by the matching resistors. In the preferred embodiment, the output transistors of the AB drivers are driven by switched current sources (Q28 and Q29) to provide enhanced current to the bases of the output transistors on an as needed basis.

Abstract: An adaptive type equalization circuit and a playback apparatus can be used for the playback of a digital signal. A playback signal is supplied to an analog to digital converter and phase lock loop such that digital conversion of the playback signal is performed. Characteristic information such as a detection signal from an envelope detector to which the playback signal is supplied, a signal showing a phase lock from the phase lock loop is supplied to a data generation circuit together with a playback signal from the analog to digital converter. The playback signal processed in the data generation circuit and its characteristic information are supplied to a processor such tat operation for weighting coefficients is performed. The weighting coefficients operated or calculated in the processor are supplied to a transversal filter so that adaptive equalization processing for the playback signal is performed.

Abstract: A symmetrical read element circuit for reducing electrical and magnetic noise using signal processing, such as a differential preamplifier. The circuits are symmetrically created on both sides of the read element so that the noise is balanced on both leads of the sensor element allowing substantial noise reduction by the signal processing. That is, the present invention provides symmetrical leads and pads designed for equal noise pickup, and for cancellation of the balanced noise.

Abstract: Asymmetry correction for an MR read head in a magnetic recording channel employs an exponential function to correct MR read head asymmetry. The asymmetry correction function has the form fASC (y)=y?q(eay+e?ay?2), wherein a is a parameter that can be adjusted for optimal channel performance, and q is an asymmetry correction coefficient.

Abstract: A storage channel, e.g., for a disk drive system, may asynchronously sample and buffer an entire sector, and then process the buffered sector to recover timing information. The storage channel may operate in an open-loop and utilize an exhaustive search to determine timing parameters. Alternatively, the storage channel may operative in a closed-loop, processing the sector once, and feeding back information obtained during decoding to the timing loop.

Abstract: Disk drive self-servo writing includes transferring a reference pattern by magnetic printing onto a reference disk, wherein the resulting printed reference pattern includes embedded servo information that provides servo timing and head position information, installing the reference disk and a head into the disk drive, reading the printed reference pattern using the head to generate a readback signal, sampling the readback signal at a sampling rate to generate a sampled signal, processing the sampled signal waveform spectrum to generate a recovered signal including the embedded servo information and fundamental and higher harmonics of the sampled signal, using the embedded servo information from the recovered signal to precisely position and maintain the head at concentric tracks of the reference disk, and self-writing servo patterns onto the tracks with the head.

Abstract: In a coding method which does not restrict a run length of “1” while data is recorded/reproduced, there are such a drawback that when an error correction is carried out, a total number of error data to be corrected is increased, and also errors of not-detectable data are increased. While data is coded, a continuous number of “1” contained in a code word is limited, and then an error correction is carried out inside a coding/decoding process operation. Thus, a recording/reproducing apparatus having a small number of decoding errors is available.

Abstract: An apparatus for providing dynamic equalizer optimization is disclosed. The present invention solves the above-described problems by providing equalizer coefficient updates that converge towards the same solution as the direct method without having to first write a known pattern to the disk or requiring any prior knowledge of the data already written on the disk. The adaptive cosine function may be used to modify only a DFIR tap set, only the j and k parameters of a cosine equalizer or to modify both the tap set for a DFIR filter and the j and k parameters of the cosine equalizer. Another algorithm, such as the LMS algorithm, may be used to modify parameters not modified by the cosine algorithm.

Abstract: An apparatus and a method to remove a resonance frequency of a system in which an unnecessary resonance frequency occurs in a head stack assembly (HSA) having a head for reading/writing data. The HSA is identified and filtered to prevent mechanical damage caused by resonance. The system is artificially excited to identify a potential resonance frequency of the system. The system is designed so that the identified resonance frequency is filtered. Thus, resonance frequency components outside of Nyquist frequency bandwidth of the system can also be identified. Also, the resonance frequency can very easily be identified in a time domain without a complicated calculation process such as an additional frequency transformation process. Coefficients of a programmable filter are updated using the identified resonance frequency to prevent mechanical damage caused by resonance and improve a servo tracking performance and reliability of data.

Abstract: Disclosed herein is an apparatus and method of calibrating the parameters of a Viterbi detector 138 in which each branch metric is calculated based on noise statistics that depend on the signal hypothesis corresponding to the branch. An offline algorithm for calculating the parameters of data-dependent noise predictive filters 304A-D is presented which has two phases: a noise statistics estimation or training phase, and a filter calculation phase. During the training phase, products of pairs of noise samples are accumulated in order to estimate the noise correlations. Further, the results of the training phase are used to estimate how wide (in bits) the noise correlation accumulation registers need to be. The taps [t2[k], t1[k], t0[k]] of each FIR filter are calculated based on estimates of the entries of a 3-by-3 conditional noise correlation matrix C[k] defined by Cij[k]=E(ni-3nj-3|NRZ condition k).

Abstract: A write driver (38) produces balanced voltages across head (32) by using the input write data (WDX and WDY) drive transistors of a slower transistor type (typically PNP) on one half of an H-bridge configuration, while transistors of a faster transistor type (typically NPN) in the other half of the H-bridge configuration are driven indirectly by transistors of the slower type, with a trans-resistance in series with transistors of the faster type. Accordingly, the voltage nodes on either side of the write head are pulled to Vcc and Vee symmetrically. A trans-resistance block (40) uses current sources to pull current from capacitive nodes for faster switching.

Abstract: An apparatus for driving a write head in response to a data signal includes: (a) a first drive unit coupled with the write head; (b) a second drive unit coupled with the write head; and (c) a control unit coupled with the first and second drive units. The control unit receives the data signal and generates control signals to the first drive and second drive units in response to the data signal. The control signals control the first drive unit to apply a first drive signal to a first write head side in a first signal polarity and control the second drive unit to apply a second drive signal to the a second write head side in a second signal polarity opposite to the first signal polarity when the data signal effects a signal excursion. The first drive signal and the second drive signal are equal in magnitude time coincident.

Abstract: A method and apparatus are disclosed for detecting data, such as a sample sequence read from a recording channel. Interpolation techniques are employed to generate one or more interpolated sample sequences from the data. Each interpolated sample sequence has a different corresponding phase relative to the data. A distance measure is generated between a portion of each interpolated sample sequence and an ideal sample sequence. The ideal sample sequence corresponds to peaks in the data. According to one aspect of the invention, a signal asymmetry measure is computed for the portion of each sample sequence and is used to adjust an ideal sample sequence.

Abstract: In one illustrative example disclosed, a magnetic storage device includes at least one magnetic disk; a magnetic head which includes first and second read sensors; a suspension which supports the magnetic head relative to the magnetic disk; and read circuitry which includes a preamplifier. The preamplifier has a first input port coupled to the first read sensor; a second input port coupled to the second read sensor; a first bias source coupled to the first input port for actively current/voltage biasing the first read sensor; a second bias source coupled to the second input port for zero biasing the second read sensor; and a subtractor having first and second inputs coupled to the first and the second input ports, respectively. The first input of the subtractor is provided with a first signal which includes a read sensor data signal and an interference signal, whereas the second input of the subtractor is provided with a second signal which includes the interference signal but not the read sensor data signal.

Abstract: Provided is a data storage device in which read and write heads can be desirably located with respect to servo tracks from the viewpoint of linearity of a PES on the premise that a read write offset exists. A read write offset value, which is a deviation amount between write and read heads in a radial direction of a disk-shaped storage medium, is set equivalent to an integer number N of servo tracks.

Abstract: An apparatus for providing data dependent detection in a data read channel is disclosed. Parameters in a read channel are dynamically adjusted according to data dependent noise. For example, a comparison in an add-compare-select (ACS) unit of a Viterbi decoder may be adjusted or offset terms in error event filters may be biased to choose a Viterbi sequence with more transitions or to compensate for polarity dependent noise.

Abstract: A media noise optimized (MNO) detector for a read channel compensates for pattern dependent media noise, and compensates for nonlinearities from many sources such as residual MR nonlinearity, residual nonlinear transition shift, partial erasure, write-induced nonlinearity, and steady-state mis-equalization. The MNO detector is implemented by adjusting a conventional Viterbi detector branch metric so that the channel output value (ideal value) can be a nonlinear function of the state/branch bits, and the branch metric scaling factor is a function of the state/branch. For a given state/branch, the ideal value is the mean of analog-to-digital converter samples for the pattern corresponding to the state/branch, and the branch metric scaling factor is proportional to the noise variance for the pattern corresponding to that state/branch.

Abstract: The present invention relates to an amplifier intended to deliver to a load impedance RL connected between two output terminals of the amplifier an output current Iout which is representative of an input signal (Vin, ?Vin) applied to two input terminals of the amplifier, which amplifier includes a first and a second transistor T1 and T2 connected as a differential pair around the load impedance RL. The amplifier according to the invention further includes a third and a fourth transistor T3 and T4 which form a differential pair; degenerated by means of a degenerating impedance Req which has a nominal value equal to that of the load impedance RL of the amplifier, which differential pair (T3, T4) is intended to be controlled by means of a control signal (?Vin/2, Vin/2), in anti-phase with the input signal (Vin, ?Vin). The invention permits to double the output current Iout of the amplifier without, however, increasing its power consumption.

Abstract: A method for characterizing a read channel of a disk drive by storing a pseudorandom number (PN) sequence at a first location on a recording surface of the disk drive, and storing the PN sequence at a second location on the recording surface. The PN sequence at the first location is read to generate a first playback signal, and a first dibit response is determined from the first playback signal. The PN sequence at the second location is read to generate a second playback signal, and a second dibit response is determined from the first playback signal. The first and second dibit responses are arithmetically combined to generate a combined dibit response in which at least some non-linear echoes are isolated.

Abstract: A remodulator embodied in an integrated circuit (IC), a method for remodulating bits and a controller and disk drive incorporating the IC or the method. In one embodiment, the IC includes: (1) a remodulator that processes incoming bits to yield remodulated outgoing bits, the remodulator including a selected one of a decision feedback loop and an error feedback loop and (2) a feedforward loop coupled to an input of the remodulator and having a baseline wander filter, the baseline wander filter cooperating with the selected one of the decision feedback loop and the error feedback loop to reduce a bit error rate of the remodulated outgoing bits.

Abstract: A first set of data is detected in a signal having synchronous samples and interpolated samples, wherein the first set of data is detected asynchronously as corresponding to one of the samples. A time to transmit a data-found signal is determined based on an offset between the data-detected sample and one of the synchronous samples, and the data-found signal is transmitted at the determined time to enable the synchronous processing of the synchronous samples. In one implementation, the synchronous samples correspond to a readback signal read from a data recording channel, the first set of data corresponds to servo address mark (SAM) data in a servo sector in the readback signal, and the synchronous processing is demodulation of burst data in the servo sector.

Abstract: A magnetic storage system includes a read element including a tunneling giant magneto-resistive (TGMR) sensor. A shunting device includes a control terminal and first and second terminals that communicate with respective first and second terminals of the read element. The shunting device shorts said first and second terminals when said control terminal is not powered to protect the read element from electrostatic discharge. A first voltage limiting circuit limits voltage that is input to first terminals of said shunting device and said read element. Said first voltage limiting circuit includes first and second diodes. An anode of said first diode and a cathode of said second diode communicate with said first terminal of said read element and said first terminal of said shunting device and a cathode of said first diode and an anode of said second diode communicate.

Abstract: An apparatus, method, and system for providing asymmetric signal correction in a HDD system using magneto-resistive (MR) heads for reading information stored thereon. The MR head produces a signal that is asymmetric, and an asymmetric correction circuit corrects the asymmetric signal for further processing. The asymmetric correction circuitry comprises a differential amplifier having a variable gain for producing a current proportional to the asymmetric signal. The differential amplifier is coupled with two high speed switches for producing an output signal having only positive polarity. When the asymmetric correction output signal combines with the input signal, the resultant signal approximates the inverse distortion of the asymmetric input signal.

Abstract: Devices and methods for generating a magnetic head-specific overshoot current which is combined with an alternating current waveform into a write current used by the magnetic head to store information on a magnetic medium. A processor analyzes the frequency of incoming write data and retrieves from a data table of an overshoot current amplitude and an overshoot current phase. This amplitude and phase information is sent to an overshoot current generator to generate an overshoot current that is responsive to the dynamic impedance properties of a magnetic write head during operation. The data table may have information related to one or many write heads, and the data table may be further subdivided based on additional dynamic characteristics of a write head that may affect the impedance thereof.

Abstract: A write driver includes two field-effect/bipolar transistors with feedbacks between the drains/collectors and gates/bases, a write/read switch connected between the drains/collectors and a positive power supply, an impedance matching circuit connected to the drains/collectors to match both differential and common mode output impedance of the write driver to an input impedance of a flex circuit, a common mode output voltage control circuit coupled to the transistors, and a differential mode output voltage control circuit coupled to the transistors.

Abstract: An information playback apparatus includes a first FIR filter, ideal signal generator, weighted equalization error calculator, and coefficient calculator. The first FIR filter generates an equalized waveform by equalizing, to a partial response waveform, a playback data string obtained by playing back a recorded signal recorded on an information recording medium. The ideal signal generator generates a target waveform serving as an equalization target. The weighted equalization error calculator calculates a data string by performing convolution computation for an equalization error which is a difference between the equalized waveform and the target waveform, on the basis of one of the playback data string and the equalized waveform input from the first FIR filter and the target waveform input from the ideal signal generator.

Abstract: In order to account for the misplacement of a write element during a servowriting process, the width of the information being written can be varied. In a self-servowriting disk drive, for example, the write current supplied to a read/write head can be adjusted to vary the width of information, such as servo bursts, written by the head. By calibrating the head and determining the misplacement of the head while writing, an edge of a servo burst can be placed in the desired position regardless of the misplacement of the head simply by adjusting the width of the written burst. This description is not intended to be a complete description of, or limit the scope of, the invention. Other features, aspects, and objects of the invention can be obtained from a review of the specification, the figures, and the claims.

Abstract: Data is read out from a disk in which the data is recorded in the perpendicular magnetic recording system by a head, amplified by a head preamplifier, and signal-processed by a read channel LSI. A read-out processing unit of a HDD controller sends out signals processed by the read channel LSI as an output of the perpendicular magnetic recording system. Further, a cut-off frequency controlling unit of the HDD controller determines a cut-off frequency of a high-pass filter of the head preamplifier based on a data transfer rate read out by the read-out processing unit, controls a cut-off frequency changing unit, and changes the value of the cut-off frequency.

Abstract: A signal processing device for analog-to-digital converting a burst signal has a feature of selecting a data bus to notify a disk control device of a conversion result via an NRZ data bus. The disk control device stores the result of the analog-to-digital conversion of the servo positional signal. The positional signal of a head of the disk device is digitized in a R/W channel. Sampling for digital conversion is performed in only a window which is defined only in the vicinity of peaks of the positional signal. The values of peaks which are obtained by sampling are averaged by an averaging circuit. This enables the influence of noise occurred outside of the window to be eliminated. Although the noise in the window is sampled, its adverse influence is suppressed by the averaging processing.

Abstract: A data storage device exhibiting reduced pad regions includes a read/write channel to convert transduced waveforms from a storage medium into recovered digital information. The recovered digital information is communicated from the read/write channel to a controller. The read/write channel includes an analog stage and a digital stage, which function independently. While the digital stage is engaged in the task of recovering servo data, the analog stage may be engaged in the task of recovering user data. Initially, the controller generates a control signal commanding the read/write channel to read and recover servo data. In the wake of the last unit of servo data having been processed by the analog stage of the read/write channel, the controller commands the read/write channel to read user data from the disc. Therefore, the analog stage of the read/write channel reads user data, while the digital stage finishes processing the servo data.

Abstract: A disk drive includes recording media having one or more recording surfaces, one or more transducer heads positionable relative to the recording surfaces by an actuator operating within a head position servo loop, and a data transfer driver. A preamplifier in the data transfer driver includes one or more head interfaces, each head interface for controlling a transducer head for read and write operations, and a mode controller for controlling each head interface based on configuration information for selectively (i) reading data from at least one recording surface, (ii) writing data to at least one recording surface, and (iii) simultaneously reading data (such as a reference pattern) from at least one recording surface and writing data (such as servo patterns) to at least one recording surface.

Abstract: The present invention discloses an apparatus (160) comprising a common mode generator circuit (162) coupled to a current directing circuit adapted to provide current to a first write head connection node (170) and to a second write head connection node (172).

Abstract: An apparatus, system, and method are disclosed for measuring magnetoresistive head assembly resistance. A measurement module measures a reference voltage across a reference resistance while applying a reference current to the reference resistance. In addition, the measurement module measures a test voltage across a first biasing resistor, a MR head assembly, and a second biasing resistor connected in series while applying the reference current to the first biasing resistor, the MR head assembly, and the second biasing resistor. A computation module calculates the MR head assembly resistance from the reference voltage, the test voltage, the reference resistance, and the resistances of the first and second biasing resistors.

Abstract: A drive and method of identifying write velocity during reading are provided. When a track is being read, the data signal is processed prior to determining the data stream to identify the velocity with which the track data were written. The read channel is adjusted based on the identified velocity to compensate for write channel transfer function variation.

Abstract: It has been discovered by the inventors that the efficiency and data integrity of a storage device can be improved by dynamically adjusting certain operating parameters to optimal values during the operation of the storage device. In one embodiment, the physical properties of a storage device such as a hard disk drive are measured during the manufacturing process to determine the dependency of the storage device upon the environmental conditions in which the storage device is operating. The physical properties of the storage device and the effect the operating environment of the storage device has upon the storage device performance are determined, and optimal values for the write current of the storage device are stored in a lookup table. The temperature in which the storage device is operating is used as a reference into the data that resides in the lookup table. Optimal values for the precompensation delay may also be stored in the lookup table.

Abstract: A method is presented for precompensation of Non-Linear Transition Shift (NLTS) in magnetic recording media using a perpendicular recording write head. The method includes maintaining a count of non-transition data bits (“zeroes”) preceding a data transition (“one”) to be written. A precompensation value is assigned which correlates to the count of non-transition data bits preceding the data transition to be written. The assigned precompensation value is then applied to delay timing of a write signal sent to the perpendicular recording write head so that the location of the actual written data transition more closely aligns with an ideal location of the data transition to be written.

Abstract: Provided is a data storage device in which servo track pitch varies within a predetermined region in a radial direction of a disk-shaped storage medium.

Abstract: A data read channel for receiving a signal containing a data stream of different types of data and recovering data therefrom, the channel comprising a main data read channel operable to output a stream of recovered data and a branch from the main data read channel comprising a signal analyser to determine the type of data from the data stream of different data types flowing in the main data read channel and a controller operable to control at least one element of the main data read channel in response to the type of data identified by the signal analyser from the data stream.

Abstract: A magnetic recording and reproducing apparatus includes a separator and first and second amplifiers. The separator separates a servo data signal and a user data signal, both reproduced by a reproducing head. The first and second amplifiers are connected to the output stage of the separator to increase the amplitude ratio of the servo data signal to the user data signal. The magnetic recording and reproducing apparatus can precisely decode the servo data along with the user data, and can achieve a highly precise servo control.

Abstract: A recording system of a magnetic tape drive is operated to cause one separate set of write heads to write data discontinuously to magnetic tape as received, and to save the data, and, during the same operation, to cause another separate set of write heads to rewrite data to magnetic tape in a continuous arrangement. The writing may be in parallel and simultaneous. Thus, during the same operation, and at the same time, the separate sets of the plurality of write heads, temporarily write the received data to magnetic tape so that the sender can erase its copy, and rewrite the saved data to the magnetic tape in a permanent arrangement, without waiting to complete first writing received data, to complete subsequently rewriting the data, and repeating.

Abstract: When a circuit that is likely to cause noise is enabled, a control circuit turns on a switch so that an inverter will be formed by one P-channel MOSFET and two parallel-connected N-channel MOSFETs. This helps enhance the current capacity of the inverter on its N-channel MOSFET side, and thereby lower the threshold voltage of the inverter.

Abstract: Disclosed are methods and circuits for impedance-controlled write drivers using matched impedance control circuits coupled in parallel with a magnetic write head.

Abstract: A dynamic threshold detector for a servo writer/detector in a magnetic storage system with a magnetic medium comprises a detector that receives data from the magnetic medium and that selects one of a first condition and a second condition based on at least one of an amplitude, a sign and bit transitions of the data. A threshold selector selects a first set of thresholds when the first condition is selected by the detector and a second set of thresholds when the second condition is selected by the detector. The data includes pairs of numbers with a first number and a a second number each having one of a positive sign and a negative sign and wherein the detector selects the first condition when the signs of the pairs are the same and the second condition when the signs of the pairs are different.

Abstract: Embodiments of the present invention relate to systems, methods, and computer readable media for calibrating storage devices such as hard drives. A testing system is connected to a group of storage devices that are being prepared for release and eventual sale. Alternately, a storage device may be connected to an end-user system for which it is in use. The storage devices are tested for head instability. A lower frequency test pattern is performed, which induces a stronger magnetic field. A measurement of servo gain control is taken while reading from a disk and compared to a baseline for servo gain control. If the variance is larger than a predetermined amount, then the read/write head is determined to be unstable.

Abstract: A write driver system comprises a control circuit that includes first switching devices and that generates gate drive signals. A write driver circuit includes second switching devices that are controlled by the gate drive signals from the control circuit. The second switching devices have higher voltage thresholds than the first switching devices. The second switching devices have slower switching times than the first switching devices.