Abstract: An error amplifier for use in a disk drive actuator system having an actuator motor for radially positioning a transducing head with respect to a rotatable disk is newly designed to enable full implementation as an integrated circuit. The error amplifier includes a switched-capacitor proportional-integral controller for comparing first and second differential input signals representing a respective actual current and commanded current for driving the actuator motor, and providing a differential output signal. A transconductor-capacitor filter is connected to filter the differential output signal of the switched-capacitor integrator, and provides a motor control signal to control the actuator motor.

Abstract: An actuator circuit includes an H-bridge having sense and power FETs to drive a voice coil motor. A differential amplifier configuration is connected to the H-bridge. A bias circuit connected to the H-bridge and to current sources controls bias current through the one sense FET and one power FET and through the other sense FET and other power FET. A common mode feedback is circuit connected to the voice coil motor to provide common mode feedback to the differential amplifier configuration. The FETs, which may be unmatched, are operated to achieve class AB operation.

Abstract: A three-phase generator boost circuit for augmenting the back electromotive force produced by a spindle motor of a disk drive is disclosed. First and second nodes provide normal connection to a source of DC voltage for the spindle motor and a second motor connected between the first and second nodes. A commutator is connected to a sequencer to operate the spindle motor. In the event of catastrophic shutdown, two of the lower commutator switches are operated to short circuit the two stator coils having the highest and lowest voltages to store energy in the coils. The commutator switches are then operated to discharge current through the nodes to a storage capacitor for the second motor.

Abstract: A power management system for an implantable device is disclosed. One application is an implantable cardioverter/defibrillator. Charging circuits for implantable cardioverter/defibrillators require relatively large currents from the power supply. The present power management system provides extended device operation and reduced charge cycle time. The present system monitors both current and voltage drawn from the power supply to prevent a loss of system voltage. Elective replacement indication is performed using charging information provided by the present power management system.

Abstract: A voltage regulator in a battery powered device, such as an implantable cardiac defibrillator, provides regulated output voltage for other circuits. When large currents are drawn from the battery, such as during charging of defibrillation output capacitors, switches decouple the regulator from receiving power from the battery and couple the regulator to receive power from a stable boost output voltage generated by a boost converter. The regulator provides a stable regulated output voltage less noisy than the boost output voltage. Controlled switch conductances in the regulator provide operation over a wide range of output load currents.

Abstract: A voltage regulator in a battery powered device, such as an implantable cardiac defibrillator, provides regulated output voltage for other circuits. When large currents are drawn from the battery, such as during charging of defibrillation output capacitors, switches decouple the regulator from receiving power from the battery and couple the regulator to receive power from a stable boost output voltage generated by a boost converter. The regulator provides a stable regulated output voltage less noisy than the boost output voltage. Controlled switch conductances in the regulator provide operation over a wide range of output load currents.

Abstract: A method and apparatus for automatically adjusting the sensing threshold in an automatic implantable cardioverter/defibrillator with pacing capability. Fixed sensitivity is used for a specified interval following each pacing pulse and automatic sensitivity adjustment is used when spontaneous cardiac depolarization is detected. For spontaneous cardiac depolarization, the sensing threshold is automatically adjusted to a value proportional to the amplitude of the sensed cardiac signal. The sensing threshold continuously decreases between sensed cardiac depolarizations, ensuring that a lower level cardiac signal will be detected. When a pacing pulse is delivered, the sensing threshold is set to a fixed value and held at that value for a predetermined period of time such that the sensing threshold will not be affected by the cardiac response evoked by the pacing pulse. At the end of the predetermined period of time, the sensing threshold is decreased as it would following a spontaneous cardiac depolarization.

Abstract: Methods are described for flocculating and removing solids suspended in water using an inorganic component containing iron, aluminum, or a mixture thereof in combination with a tannin-based flocculant produced by reacting a condensed tannin with an amino compound and an aldehyde. The tannin-based flocculant is preferably the product of a controlled reaction in which the viscosity is monitored as an indication of suitable shelf life.

Abstract: Methods and arrangements for associating control messages received in the D-channel of an integrated services digital network (ISDN) line with the call control process to which the message relates are disclosed. With ISDN, a single control channel, called the D-channel, can be used concurrently to control a plurality of calls. As each call is initiated, a call control process and data structure including the unique identity of the call, are created. The data structures associated with the same D-channel are linked together. When a control message including a given identity is received, the data structures associated with the D-channel conveying the message are searched in sequence until a data structure having the given identity is found. The contents of this data structure are used to access the control process associated therewith. When the search reveals no matching identity and the message is a call setup message, a new process and data structure are created.

Abstract: A composition and method are described for flocculating and removing solids suspended in water using an inorganic component containing iron, aluminum, or a mixture thereof in combination with a tannin-based flocculant produced by reacting a condensed tannin with an amino compound and an aldehyde. The tannin-based flocculant is preferably the product of a controlled reaction in which the viscosity is monitored as an indication of suitable shelf life.