Abstract: One embodiment includes a pulse duration control system for a magnetic disk-drive system. A rise delay system generates first control voltages in response to a write data input signal changing between a first state and a second state. A fall delay system generates second control voltages in response to the write data input signal changing between the first and second states. A comparator system generates a rising-edge overshoot signal and a falling-edge overshoot signal based on a comparison of the first and second control voltages. The rising-edge overshoot signal can set a duration of a positive overshoot current pulse for a write current at a transition of the write data input signal from the first state to the second state, and the falling-edge overshoot signal can set a duration of a negative overshoot current pulse for the write current at a transition from the second state to the first state.

Abstract: Apparatus and systems create differential drive signals suitable for HAMR data recording. A laser diode differential driver provides heating current pulses at a time ?1. The pulses energize a laser diode to pre-heat the magnetic medium to be written. Some embodiments duplicate portions of the laser diode circuit architecture to create a magnetic write head differential driver. The write head driver provides write current pulses to a magnetic write head in one direction with ?1 timing and in the opposite direction with ?2 timing. Both drivers utilize sets of reference voltages capable of being switched to one terminal or the other of the element to be driven. In the laser diode case, the common mode is split between the anode and cathode sections of the driver. A feedback element is added between the cathode and anode sections to provide current accuracy independent of the electrical characteristics of the selected laser diode.

Abstract: Apparatus and systems create differential drive signals suitable for HAMR data recording. A laser diode differential driver provides heating current pulses at a time ?1. The pulses energize a laser diode to pre-heat the magnetic medium to be written. Some embodiments duplicate portions of the laser diode circuit architecture to create a magnetic write head differential driver. The write head driver provides write current pulses to a magnetic write head in one direction with ?1 timing and in the opposite direction with ?2 timing. Both drivers utilize sets of reference voltages capable of being switched to one terminal or the other of the element to be driven. In the laser diode case, the common mode is split between the anode and cathode sections of the driver. A feedback element is added between the cathode and anode sections to provide current accuracy independent of the electrical characteristics of the selected laser diode.

Abstract: A hard drive write preamplifier includes a first differential pair of PNP BJTs having a first PNP BJT and a second PNP BJT; a first tail current source coupled into emitter of the PNP BJTs of the first differential pair; a second differential pair of NPN BJTs having a first NPN BJT and a second NPN BJT; a second tail current source coupled into the emitters of the NPN BJTs of the second differential pair; wherein a collector of each of the PNP BJTs of the first differential pair are coupled to a corresponding collector the NPN BJTs of the second differential pair; a first shift up PNP BJT having emitter coupled to the collector of a first PNP BJT of the first differential pair; a second shift up PNP BJT having an emitter coupled to the collector of the second PNP BJT of the first differential pair.

Abstract: A hard drive write preamplifier includes a first differential pair of PNP BJTs having a first PNP BJT and a second PNP BJT; a first tail current source coupled into emitter of the PNP BJTs of the first differential pair; a second differential pair of NPN BJTs having a first NPN BJT and a second NPN BJT; a second tail current source coupled into the emitters of the NPN BJTs of the second differential pair; wherein a collector of each of the PNP BJTs of the first differential pair are coupled to a corresponding collector the NPN BJTs of the second differential pair; a first shift up PNP BJT having emitter coupled to the collector of a first PNP BJT of the first differential pair; a second shift up PNP BJT having an emitter coupled to the collector of the second PNP BJT of the first differential pair.

Abstract: A control circuit to provide a control current to control an amplitude of a write current in a magnetic media drive. The control circuit has an output circuit for providing the control current with an amplitude dependent on a bias voltage. A bias current path provides the bias voltage to the output circuit, and a current diverting circuit is connected to divert current from the bias current path. A programmable ramp voltage generator operates in response to a degauss enable signal, and a voltage-to-current converter receives the programmable ramp voltage to control the current diverting circuit to divert current from the bias current path at a rate determined by the programmable ramp voltage. The bias voltage and the write current decay according to the programmable ramp voltage. The write current decay can be made linear and independent of a beginning write current amplitude.

Abstract: One embodiment of the invention includes a system for writing data onto a magnetic disk. An output driver provides a first write current through a first output transistor in a first state and provides a second write current through a second output transistor in a second state. The first and second write currents can be provided to a disk write head to store opposing binary values, respectively. A bias current generator switches a first bias current between an intermediate voltage node in the second state and a first control node in the first state, and switches a second bias current between the intermediate voltage node in the first state and a second control node in the second state. The first and second bias currents can be provided to set a bias voltage at the first and second control nodes to bias the first and second output transistors, respectively.

Abstract: One embodiment of the invention includes a system for writing data onto a magnetic disk. An output driver provides a first write current through a first output transistor in a first state and provides a second write current through a second output transistor in a second state. The first and second write currents can be provided to a disk write head to store opposing binary values, respectively. A bias current generator switches a first bias current between an intermediate voltage node in the second state and the first control node in the first state, and switches a second bias current between the intermediate voltage node in the first state and the second control node in the second state. The first and second bias currents can be provided to set a bias voltage at the first and second control nodes to bias the first and second output transistors, respectively.

Abstract: A control circuit to provide a control current to control an amplitude of a write current in a magnetic media drive. The control circuit has an output circuit for providing the control current with an amplitude dependent on a bias voltage. A bias current path provides the bias voltage to the output circuit, and a current diverting circuit is connected to divert current from the bias current path. A programmable ramp voltage generator operates in response to a degauss enable signal, and a voltage-to-current converter receives the programmable ramp voltage to control the current diverting circuit to divert current from the bias current path at a rate determined by the programmable ramp voltage. The bias voltage and the write current decay according to the programmable ramp voltage. The write current decay can be made linear and independent of a beginning write current amplitude.

Abstract: A write channel for a hard disk drive has a write current with a programmably adjustable rise time, and includes first and second analog write data signal paths having respective resistive nodes. First and second programmable capacitors are connected to the resistive nodes, whereby changes in capacitance of the first and second capacitors changes the rise time of the write current. A programmer selectively programs the first and second programmable capacitors. The rise time programmed is selected to provide a decreased bit error rate of an on-track write process and reduced adjacent-track interference.

Abstract: Methods and apparatus for generating a hard drive write signal are here in disclosed. A disclosed method comprises generating a hard drive write signal on an output of a switch based on an edge of the first control signal and reducing the hard drive write signal based on an edge of a second control signal via a second switch.

Abstract: A circuit for providing a write current having a programmably adjustable duty cycle in a hard disk drive write channel has a differential pair gain circuit for receiving a data input signal and generating a differential output voltage to provide a differential write signal for generating the write current. First and second programmable current sources are connected to the differential pair gain circuit to create a programmable voltage offset of the differential output voltage to programmably adjust the duty cycle of the write current.

Abstract: One embodiment of the invention includes a driver circuit. The driver circuit comprises an output transistor that is biased to provide an output signal in response to an input signal. The driver circuit also comprises at least one programmable variable resistor configured to provide a bias magnitude of the output transistor that sets a power of the driver circuit to be commensurate with a data-rate of the input signal.

Abstract: Methods and apparatus for temperature compensation for hard disk drive writer overshoot current are disclosed. A disclosed system comprises creating a first delay based on the temperature of the hard disk drive, creating a second delay based on the temperature of the hard disk drive, and creating a pulse based on the first and second delay.

Abstract: Methods and apparatus to for low power hard disk drive servo writers. A disclosed servo writer comprises a distribution circuit to receive one or more pulses from a pulse generator, the distribution circuit having a biasing circuit have one of a first write mode or a second write mode based on an operating condition signal; and a first signal generator to form a first write signal and a second signal generator to form a second write signal, the first and second signal generators being actuated by the distribution circuit, wherein the distribution circuit actuates one of the first and second signal generators in the first write mode and the distribution circuit actuates the first and second signal generators in the second write mode.

Abstract: One embodiment of the invention includes a current mirror system. The system comprises a master circuit configured to conduct a first current in response to an activation state of an activation signal. The system also comprises a slave circuit configured to generate at least one second additional current in response to the activation state of the activation signal. Each of the at least one additional current can be proportional to the first current. The system further comprises a current path circuit that is configured as a substantial copy of the master circuit, the current path circuit being configured to conduct the first current in response to a deactivation state of the activation signal.

Abstract: The present invention achieves technical advantages as a preamplifier write driver (10) having a varying common-mode output voltage. This varying common-mode output voltage also adjusts the derivative of the common-mode voltage, which is proportional to the amount of current coupled onto the MR head through parasitic capacitance. Currents of a first circuit (Q0,Q3) and a second circuit (Q1,Q2) are matched to overcome process variations and modeling errors. A pair of transresistance amplifiers (16) are driven by control lines (14) to achieve these matched currents.

Abstract: One embodiment of the invention includes a driver circuit. The driver circuit comprises an output transistor that is biased to provide an output signal in response to an input signal. The driver circuit also comprises at least one programmable variable resistor configured to provide a bias magnitude of the output transistor that sets a power of the driver circuit to be commensurate with a data-rate of the input signal.

Abstract: One embodiment of the invention includes a system for writing data onto a magnetic disk. An output driver provides a first write current through a first output transistor in a first state and provides a second write current through a second output transistor in a second state. The first and second write currents can be provided to a disk write head to store opposing binary values, respectively. A bias current generator switches a first bias current between an intermediate voltage node in the second state and the first control node in the first state, and switches a second bias current between the intermediate voltage node in the first state and the second control node in the second state. The first and second bias currents can be provided to set a bias voltage at the first and second control nodes to bias the first and second output transistors, respectively.

Abstract: One embodiment of the invention includes a driver circuit. The driver circuit comprises a high-side switch that is activated in response to a positive driver input signal to provide a positive output signal at a driver output. The driver circuit also comprises a low-side switch that is activated in response to a negative driver input signal to provide a negative output signal at the driver output. The positive and negative driver input and output signals can be relative to respective cross-over magnitudes. The driver circuit further comprises at least one impedance-matching device configured to activate the low-side switch in response to a positive signal reflection at the driver output and to activate the high-side switch in response to a negative signal reflection at the driver output.