Abstract: An improved write drive circuit which includes a discharge circuit added to the base of the bottom transistors of the H-bridge to prevent excessive overshoot and ringing while allowing for higher data rates. The discharge circuit is turned on after the head voltage or current reaches an overshoot condition. In preferred embodiments, the discharge circuit includes variable discharge capability by selecting one or more parallel drive transistors or varying a variable delay in the discharge circuit or any combination of both variables. Both can be controlled by a word written to the disk drive pre-amp over the serial control port.

Abstract: An inductive load driver circuit including a first switch that switches between a conductive state and a non-conductive state selectively applies a first power supply potential to a first side of the inductive load in response to a control signal. A second switch that switches between a non-conductive state and a conductive state selectively applies a second power supply potential to a second side of the inductive load in response to the control signal. The control signal places a control node of the second switch at a lower potential than the second side of the inductive load while the second switch is in the conductive state. In operation, a steady state current in a first direction is driven through the inductive load. The nodes of the inductive load are placed in a high impedance state, after which a steady state current is driven in a second direction through the inductive load.

Abstract: There is disclosed a video playback device for playing back a recorded television program in time-compressed mode on a display screen coupled to the video playback device. The video playback device comprises: 1) a disk storage system for storing the recorded television program as a plurality of audio-video segments; and 2) a fast playback controller for determining a limited time period during which the recorded television program must be played back and further capable of using at least one priority value associated with each of the plurality of audio-video segments to identify selected ones of the plurality of audio-video segments capable of being sequentially played-back during the limited time period.

Abstract: The invention provides a write driver circuit for writing an information signal on a magnetic record carrier. The write driver circuit comprises a first and a second input terminal (20,22) for receiving the information signal. A first current sink (24) is available, having a first transistor (T3) of a first type, having a first main electrode coupled to the first point of constant potential (+), having a second main electrode coupled to the first input (34) of a write head combination (32) via a first impedance (38), and a control electrode coupled to the first input terminal (20). A second current sink (28) is available having a second transistor (T4) of the first type, having a first main electrode coupled to the first point of constant potential (+), having a second main electrode coupled to the second input (36) of the write head combination via a second impedance (42), and a control electrode coupled to the second input terminal (22).

Abstract: A method and apparatus for high voltage applications, with the latest MOSFET technology having limited terminal-to-terminal voltage capability, includes a switch circuit having at least two serially coupled MOSFETs and a two-stage MOSFET connection using a plurality of resistors, and/or a bipolar transistor, and a plurality of diodes. One of the high voltage applications is a high speed write driver in a computer disk drive. The switch circuit switches on/off between zero volt and a voltage higher than a maximum terminal-to-terminal voltage of a single MOSFET which is typically five volts. A required voltage in high voltage applications can be in excess of, for example, 8 or 9 volts.

Abstract: A method of calibrating a write current-setting for writing servo sectors onto a recording surface through a head in a head disk assembly of a disk drive is disclosed. A preamplifier circuit has an input for receiving a selected control signal set by a current-setting value, the preamplifier circuit causing current to flow through the head with a current magnitude determined by the current-setting value. A multiple-pass process is performed in which a series of current-setting values are set for the control signal for generating a plurality of quality metrics each indicative of a quality of the selected control signal. Each pass in the multiple-pass process includes the steps of providing a data sequence to the preamplifier circuit to cause a test pattern to be written to the recording surface, and reading the test pattern and generating and storing at least one of the plurality of quality metrics.

Abstract: A method is disclosed for controlling the write head of a magnetic disk storage device. The method includes sinking current from the first terminal of the write head and sourcing current to the second terminal of the write head substantially simultaneously with sinking current from the first terminal so that a first steady state voltage level appears on the first terminal of the write head and a second steady state voltage level appears on the second terminal thereof that are approximately at a midpoint between a high reference voltage level and a low reference voltage level. The common mode voltage of the write head is substantially constant over time.

Abstract: A method and circuit are disclosed for controlling the write head of a magnetic disk storage device. The circuit includes a pull-up device coupled to a terminal of the write head, a current sink circuit which is coupled to the write head terminal and a bootstrap circuit coupled to the current sink circuit. When reversing the direction of current flow through the write head so that current is drawn from the write head from the write head terminal, the bootstrap circuit and the current sink circuit are activated. When the current in the write head nears and/or slightly surpasses the desired destination current level, the bootstrap circuit is deactivated and the pull-up device is thereafter immediately activated for a predetermined period of time.

Abstract: A write circuit selectively provides a write current through a write head in first and second opposite directions. The write circuit is connected to the write head by an interconnect, and has a positive supply level and a negative supply level. A first voltage source provides a first control voltage, and a second voltage source provides a second control voltage. A first resistor is provided between the first voltage source and the interconnect for impedance matching to the interconnect, and a second resistor is provided between the second voltage source and the interconnect for impedance matching to the interconnect. The first and second control voltages provide a transient voltage to the interconnect and provide a subsequent steady-state voltage to the interconnect.

Abstract: An information recording device which records information at a high recording density such that an error rate is reduced. In particular, an information recording device that includes a recording head, arranged near or to be close to the recording medium, for applying magnetic fields to the small regions when the recording head relatively moves with respect to the recording medium to pass on the small regions of the recording medium, and a recording head controller for controlling the recording head to cause the recording head to apply magnetic fields to the small regions in a free region of the recording medium in a standby state in which at least information is not recorded on the recording medium to uniform the directions of magnetization of the small regions so as to erase the information in the predetermined free region.

Abstract: A method and circuit are disclosed for controlling the write head of a magnetic disk storage device. The circuit includes a pull-up device and a current sink circuits coupled to each terminal of the write head, for selectively sourcing current to and sinking current from the write head, respectively. A clamp device is coupled to each write head terminal to selectively clamp the write head terminals to steady state intermediate voltage levels. The circuit further includes a control circuit for individually activating the pull-up devices, the current sink circuits and the clamp devices. In particular, when reversing the direction of current flow through the write head from a first direction in which current is provided to the write head via the write head terminal to a second direction in which current is drawn from the write head from the write head terminal, the appropriate pull-up device is activated for a predetermined period of time.

Abstract: A write driver controls current path for current of an H-bridge circuit. The H-bridge circuit is controlled by a differential pair switch for adjusting a voltage between the differential pair switch between a first voltage when the H-bridge circuit is switched and a second voltage after the H-bridge circuit is switched.

Abstract: A write output driver with internal programmable pull-up resistive devices is disclosed. The write output driver provides an integrated output driver circuit configurable to provide near end transmission line termination. The output driver is configured to provide transmission of a high-speed signal with increased frequencies over prior output drivers. The output impedance of the output driver is programmable and maintained substantially constant, despite ambient fluctuations. An internal bias signal generator is provided to control the impedance of the output driver.

Abstract: A write head is described having a switchable damping resistance coupled in parallel with an inductor. The damping resistance is decoupled from the inductor by rendering a transistor nonconductive when a direction of current in the inductor changes. The damping resistance is then coupled to the inductor before oscillations begin in the current in the inductor. The decoupling of the damping resistor eliminates power dissipation in the damping resistor during a change in the direction of current in the inductor.

Abstract: A circuit (50) and method are provided for generating a signal (84) indicating an open impedance fault of a coil (56) of a write head (18) of a mass data storage device (10). The circuit (10) includes a differential amplifier (51) with the electrical component (56) being connected as a load in a first leg thereof. An impedance element (64) is provided in a second leg of the differential amplifier (50), and a pair of bipolar transistors (52,54) are respectively connected in the first and second legs. The pair of bipolar transistors (52,54) have a constant bias voltage (Bias) applied to inputs thereof, and an output circuit is connected to an output node of the first leg of the differential amplifier (51).

Abstract: A magnetic disk read/write circuit comprises a core having a pair of coils wound such that signals supplied to the coils becomes opposite in phase and a read circuit having a first input terminal connected to one of terminals of a read head through one of the coils to receive a read signal from the read head and a second input terminal connected to the other terminal of the read head through the other coil to receive the read signal from the read head or a write circuit in which the read head is a write head, the signal at the first input terminal is a signal at the first output terminal and the signal at the second input terminal is a signal at a second input terminal.

Abstract: A transconductance circuit having a high output impedance has a dual input differential transconductor (10) with first (14) and second (16) differential inputs and a differential output (18). The first differential input (14) is connected to receive a dc voltage (20). An inverting feedback path is connected between the second differential input (16) and the differential output (18). A differential difference amplifier (24) has a first input (26) connected to receive the dc voltage (20) and a second input (28) connected to the inverting feedback path. A variable resistor (22) is connected across the differential output (18). The output (30) of the differential difference amplifier (24) is connected to control the variable resistor (22) to minimize the output of the differential difference amplifier (24), thereby creating a high output impedance from said transconductor (10).

Abstract: Apparatus and method for writing data to a magnetic recording medium in the form of magnetization vectors having alternating magnetic orientations and lengths ranging from a minimum symbol length to a maximum symbol length. A write element adjacent the medium includes a leading edge and a trailing edge to form a write gap which generates a write gap recording field having a length substantially greater than the minimum symbol length. A write driver applies a write current signal to the write element as a series of current pulses, each pulse magnetizing an area of the disc corresponding to the length of the write gap recording field. A subsequent current pulse is applied while a portion of a first area magnetized by a previous pulse remains disposed between the leading edge and the trailing edge of the write element, so that the remaining portion of the first area beyond the trailing edge of the write element forms a magnetization vector of selected symbol length.

Abstract: The present invention achieves technical advantages as an overshoot circuit (30) for a voltage source/impedance based write coil driver circuit (10) accurately controlling the current (IW)through a coil (LH) that is used to write data to a magnetic medium. The circuit (30) improves the characteristics of the coil.

Abstract: A method for controlling write current to a write head during data write on a hard disk drive is disclosed. A direct access storage device includes a rotating storage medium in which data are magnetically written, a write head for writing data in the rotating storage medium, and a write current control circuit for changing write current-value settings to be supplied to the write head according to a predetermined elapsed time from the beginning of a write operation.

Abstract: There is disclosed a write compensator which suppresses bit shift caused by distortion of a read signal waveform of a read head in a disk drive adopting a perpendicular magnetic recording system. The write compensator executes write compensation during recording data based on the known relationship between bit shift which is beyond an allowable range and a pattern of a data bit string of a data signal. A write amplifier converts the write-compensated data signal into an electrical signal by using the write compensator so as to suppress the bit shift, and supplies it to a write head.

Abstract: A magnetic recording and reproducing apparatus includes a read/write signal processor having a write data generator arranged to be of an interleave system and transmitting/receiving data to/from the read/write amplifier via a plurality of signal lines. In addition, the read/write amplifier has a compound circuit provided for the write data of the interleave system from the read/write signal processor and is formed as an integrated circuit, moreover, a 1/2 prescaler is provided at the output of the write data generator, transmitting and receiving write data in Non-Return-To-Zero-Interleave CODE.

Abstract: A method (and magnetic recording circuit structure) for write drivers to reduce the reversal time for the current through the inductive recording head, includes a write driver output stage providing a write signal output with a write signal source strength S0, a magnetic write head with a write signal input essentially equal to strength S0, and an interconnect circuit having a characteristic impedance Z0 coupled to the write signal output of the write driver output stage and the magnetic write head. The write driver output stage preferably includes a source-side termination circuit having output impedance ZS, wherein the source-side termination circuit output impedance ZS is substantially equal to Z0 and the source strength S0 of the write driver at the input of the interconnect circuit is temporarily enlarged after every polarity reversal of the write signal for a predetermined time duration &Dgr;t.

Abstract: A transformer-coupled tape drive (30) allows operation using a direct current (DC) content code. Usage of the DC content code is facilitated by a compensation circuit (240) which corrects timing distortion caused by the DC content code. The compensation circuit comprises both an emulation circuit (306) and a delay circuit (302). The emulation circuit (306) emulates a high pass filter action of a transformer (220) to provide an emulated high pass filter response signal (WD_HP). The delay circuit (302) modifies the modify timing of the write data signal in accordance with the emulated high pass filter response signal to output a compensated write data signal to the transformer (220).

Abstract: In the magnetic record writing circuit, an arrangement is provided such that, a current having a higher level than a level of a write current is supplied for a desired period of time during rise and fall of the write current, and a current having a lower level than the level of the write current is supplied for a desired period of time during overshoot at the rise and fall of the write current. Accordingly, the write current can be recovered quickly from the overshoot.

Abstract: A system and method are provided for calibrating a corner frequency of a tunable filter using an ADC code difference method. A method for calibrating a corner frequency of a tunable filter in a direct access storage device includes generating a signal having a frequency within a pass band of the tunable filter to be passed to the tunable filter. The gain of the signal is adjusted to a first threshold level. The corner frequency of the signal is shifted to a second threshold level, whereby the corner frequency of the tunable filter is calibrated at a desired frequency. A system for calibrating a corner frequency of a tunable filter in a direct access storage device includes calibrate control logic coupled to a tunable filter. A signal source generating a signal having a frequency within a pass band of the tunable filter to be passed to the tunable filter is coupled to the tunable filter by a variable gain amplifier. An analog-to-digital converter (ADC) is coupled to the tunable filter.

Abstract: A head amplifier circuit supplies a writing current, having a direction in accordance with recording information, to a head for recording information on a recording medium. The head amplifier circuit includes a reference voltage generating portion for generating a reference voltage, a constant current generating portion for generating a constant current based on the reference voltage generated by the reference voltage generating portion, and a grounding portion. During one period of time, the constant current generating portion supplies the constant current to a first end of the head and the grounding portion grounds a second end of the head. During another period of time, the constant current generating portion supplies the constant current to the second end of the head and the grounding portion grounds the first end of the head.

Abstract: A write driver, having a pair of head nodes for connection to a write head, includes two diodes connected, respectively to the head nodes and the emitters of first and second upper drive transistors. The diodes increase the voltage necessary to breakdown the emitter pn junctions of the upper drive transistors, thereby enabling a greater head swing voltage, higher switching rates, and ultimately closer spacing of data on a magnetic medium.

Abstract: Adaptive channel optimization in a disk drive is achieved by selecting a track of the recording medium and then writing a first data pattern to opposite sides of the selected track. The first data pattern is written a certain percentage off-track in relation to the centerline of the selected track. A second data pattern is then written directly on the selected data track and the off-track margin is determined as a function of how far the recording head can be positioned away from the center of the selected track during reading of the second data pattern while meeting a specified error rate. The off-track margin test is repeated iteratively using a combination of channel variable settings in order to find a set of variable settings which provides an optimal performance criterion for the drive.

Abstract: A write driver to supply current to an induction load, including an H-bridge circuit coupled to the induction load to switch the current between a first current path and a second current path, said induction load operative to generate an undershoot current, and an undershoot circuit to control the undershoot current based on a comparison of a reference voltage and a flyback voltage. The undershoot circuit is connected to bases of the transistors of the lower H-bridge circuit.

Abstract: A magneto-resistive head preamplifier structure has a difference amplifier with cross-coupled transistors configured to cancel the adverse effects on preamplified output signals due to parasitic capacitance associated with the difference amplifier transistors. The cross-coupled transistors extend the useable bandwidth of the preamplifier by substantially reducing internally generated thermal noise.

Abstract: A switchable voltage follower and a bridge driver that utilizes the voltage follower. The voltage follower has an output transistor pair, three switching devices and an operational amplifier. Each of the switching devices is controlled by a polarity terminal for switching the circuit to be a pull-up voltage follower or a pull-down voltage follower. The bridge driver is formed by two switchable voltage followers to provide a bridge push-pull driving capability by driving the two switchable voltage followers alternately.

Abstract: Programmable active damping of the overshoot in the bipolar write driver output current waveform in the write head of a hard disk drive is provided by subtracting, a controlled amount of current from the writer current, for a predetermined duration, at the beginning of each transition of the write driver output current.

Abstract: To restrain noise voltage output caused by a rapid change in output current in starting an output stage, a reproduced signal detected by an MR head is amplified by an amplifier and out-put volt-age and output current are outputted, A middle point of the MR head is controlled to always maintain potential of ground level. The output current is controlled by a current control portion (delaying circuit) (not included in FIG. 1) for converting an ON/OFF control signal into a signal having an integration waveform. The signal having the integration waveform is provided with a rise portion having a constant time constant, thereby there is restrained noise voltage output caused by a rapid change in output current, hunting of a power source of an amplifying portion, or inner inductance in a conventional example.

Abstract: A head suspension assembly for use in a magnetic disk drive includes a magnetic head constituted by a magnetoresistive element for reading data and a head element for writing data, a slider for holding the magnetic head above a surface of a rotating magnetic recording medium, a suspension for supporting the slider, and a head integrated circuit mounted on the suspension. The head integrated circuit having a built-in protection circuit electrically connected with the magnetoresistive element to protect the magnetoresistive element from electrostatic breakdown. Thereby, the magnetic head can be efficiently prevented from suffering electrostatic breakdown due to, e.g., electrostatic discharge occurring during the assembly process of incorporating the head suspension assembly into the magnetic disk drive.

Abstract: An improved write drive circuit which provides an adjustable writer drive current and overshoot transient for a H-bridge drive circuit in a hard disk drive. The invention uses a variable capacitor circuit to give an initial boost to the write driver transistors. In a preferred embodiment, the capacitance of the variable capacitor is controlled by a word written to the disk drive pre-amp over the serial control port.

Abstract: Apparatus for improving data writing operations to a disc recording surface of a disc drive. A head assembly is supported over the disc recording surface by a flexible suspension assembly of a controllably positionable actuator assembly and includes a write current shaping circuit integrated with a write element. The write current shaping circuit modifies write currents received by the head assembly via a transmission line from a preamplifier driver circuit to remove undesired characteristics from the received write currents. The write element writes data to the disc recording surface using the write currents as modified by the write current shaping circuit.

Abstract: A precompensation write circuit includes a ring oscillator (100), a pluse interpolator circuit 200, a data pattern sequence detector circuit 300, a precoder circuit 400, a data reference reframe circuit 500, a data coalscer circuit 600 and an isolation mux circuit 700.

Abstract: A disk drive includes a disk having a recording surface and a write element for writing a sequence of symbols in a continuous-time signal on the recording surface. The disk drive includes a frequency generator for generating a plurality of primary phase write clock signals having a channel frequency fch. Each of the primary phase write clock signals has a selected primary phase shift from another one of the primary phase write clock signals. The disk drive includes a programmable phase synthesizer for generating a secondary phase write clock signal having the channel frequency fch and a selected secondary phase shift from one of the primary phase write clock signals. The programmable phase synthesizer includes programmable means for selecting two of the primary phase write clock signals and element for performing vector addition of the selected primary phase write clock signals to generate the secondary phase write clock signal.

Abstract: A magnetic recording apparatus has a magnetic head for writing data to a magnetic disk, a writing circuit for feeding a current to the magnetic head, a controller for controlling the operation of the writing circuit, and a temporary shutoff circuit for shutting off the current temporarily while the operation of the controller is in a transient period. The writing circuit has a first transistor, which is connected to the magnetic head. The temporary shutoff circuit has a second transistor so as to temporarily deactivate and thereafter activate the first transistor when electric power starts being supplied by pulling into the second transistor the transient current resulting from variation in the base voltage of the second transistor as a result of the parasitic capacitor present at the base of the second transistor being charged when electric power starts being supplied.

Abstract: An improved write drive circuit which provides an adjustable writer drive current and overshoot transient for a H-bridge drive circuit in a hard disk drive. The invention uses a variable capacitor circuit to give an initial boost to the write driver transistors. In a preferred embodiment, the capacitance of the variable capacitor is controlled by a word written to the disk drive pre-amp over the serial control port.

Abstract: A magnetic disk unit includes slider suspension assemblies, each of the assemblies having a slider with at least one magnetic head element and a suspension with one end portion and one surface, the slider being mounted on the one surface of the suspension at the one end portion, magnetic disks, each of the disks having at least one surface which opposes to the slider of the assembly, head IC chips electrically connected to the magnetic head elements, and a control circuit electrically connected with the head IC chips. The control circuit controls operations of each of the magnetic head elements so that the write current is applied to the magnetic head element for a first predetermined period of time and then the application of the write current to the magnetic head element is stopped for a second predetermined period of time which is equal to or longer than the first predetermined period.

Abstract: A magnetic recording circuit includes a write driver output stage, a magnetic write head and an interconnect circuit. The write driver output stage has an output and an output impedance. The magnetic write head has an input and an input impedance. The interconnect circuit has an input, an output and a selected characteristic impedance Z0. The input of the interconnect circuit is coupled to the output of the write driver output stage, the output of the interconnect circuit is coupled to the input of the write head. The interconnect circuit can be one of, or both, source-terminated so that the output impedance of the write driver output stage is substantially equal to the selected characteristic impedance Z0 of the interconnect circuit, and load-terminated so that the input impedance of the write head is substantially equal to the characteristic impedance Z0 of the interconnect circuit.

Abstract: A disc drive storage system and device is provided in which distortion in a drive signal due to a mismatch between a signal source impedance and a write head impedance is minimized. A write head that writes on a disc surface and a signal source that provides a drive signal to the write head are coupled by an electrical interconnect path. A connection device that minimizes the mismatch between the signal source impedance and the write head impedance is introduced in the electrical interconnect path. In addition, a method of coupling a signal source to a write head in a disc drive storage system is provided.

Abstract: A recording apparatus for recording an information signal on a magnetic record carrier includes a write driver circuit and a magnetic write head. The write driver circuit comprises a first voltage driver and a second voltage driver. A first current driver and a second current driver are present for driving the write head. The first and second voltage driver each include a respective series circuit of an npn transistor and a bidirectional impedance element coupled between a point of constant potential and the respective outputs of the first and second voltage drivers.

Abstract: A method, devices, and an article of manufacture for reducing magnetic instability in a magnetoresistive read head of a combined read-write head after writing data onto a magnetic storage medium. The last write pulse polarity that results in the least amount of magnetic instability in the read head is determined, and is referred to as the designated polarity. Then, after a set of write pulses is written, it is determined whether the last write pulse has the designated polarity. If the last write pulse does not have the designated polarity, then an additional write pulse with the designated polarity is written. Thus, the last write pulse before a read always has the designated polarity, thereby reducing the magnetic instability of the read head, and consequently improving read head performance.

Abstract: A preamplifier chip for a disk drive is modular in layout. Twelve head cells for the preamplifier chip are not lined along the periphery of the chip, but rather are disposed in an array including four rows of three head cells each. The rows are all directed perpendicular to the side with control connection pads. The preferred embodiment allows for a smaller preamplifier chip through increasing the density of head cells on the chip relative to the periphery of the chip usable for head cell connection. The array spaces write portions of the head cells in four spaced lines, minimizing problems associated with heat build up. Spacing between rows of the array can be determined to take maximum advantage of lead pitch on the flex circuit. Modification of the design to a chip for eight or four channels is possible with minimal changes to the design, and minimal reworking of the common circuitry.

Abstract: A disk drive comprising a plurality of recording surfaces and plurality of associated heads is disclosed employing a n-current preamplifier for generating n independently controlled write currents. For example, the n-current preamplifier may be employed during manufacturing of the disk drive to simultaneously write servo sectors to all of the recording surfaces in a “bank servo write” mode. The n-current preamplifier comprises an input for receiving a plurality of current-setting control signals corresponding to the plurality of heads, and a plurality of signal-to-current converters for converting the current-setting control signals into a plurality of write currents for the heads, wherein each write current has a magnitude that is independently controlled by a respective one of the current-setting control signals.

Abstract: A device is described for increasing the rate at which data may be written to a magnetic data storage medium. The device includes circuitry for amplifying the data and circuitry for writing the data to a data storage medium. The circuitry for amplifying the data includes: circuits for amplifying the data; delaying and amplifying the data; and adding the amplified data and the delayed and amplified data.

Abstract: A device for writing information to a magnetic medium includes an inductive head and a write amplifier coupled to the inductive head. The write amplifier receives an information signal, and amplifies the signal to provide a current through the inductive head to generate a flux at the inductive head which flux writes a bit of the information on the magnetic medium. The current for each bit of information is characterized by a rising portion, a peak portion, and a settling portion. A damping network is coupled to the inductive head, and couples a low impedance path to the head and the write amplifier, after the current reaches the peak portion, to divert current from the head to reduce a duration of the settling portion of the current. The write amplifier and damping network are embodied together in an integrated circuit, and are programmable via a serial interface.