Abstract: A circuit and method for an integrated multifunction voltage regulator is disclosed. The integrated circuit features a voltage preregulator having a battery input and a Vcc output, a voltage bus for distributing the Vcc voltage, and a plurality of function blocks which are connected to the Vcc buss and are driven by the Vcc voltage. The function blocks include voltage regulators, protected battery switches, band gap voltage references, and reset circuits.

Abstract: A stator coil driver circuit for a brushless DC motor, which minimizes torque ripple by keeping the current in the commutating phases constant, is disclosed. The circuit includes a slew rate control circuit for ramping up the current or ramping down the current during commutation. The slew rate control circuit consists of a capacitor, a first current source for charging the capacitor, and a second current source for discharging the capacitor. The circuit also includes a sense resistor or a sensefet and an operational transconductance amplifier for providing feedback control.

Abstract: A stator coil driver circuit for a brushless DC motor, with an improved current mirror, is disclosed. The improved current mirror has a first transistor which conducts current and a second transistor configured to mirror the current of the first transistor. Additionally, the improved mirror circuit includes a unity gain amplifier connected in between the gates of the first and second transistor. The effect of the unity gain transistor is to provide for a faster turn-off of the second transistor and reduce oscillation of the circuit.

Abstract: A comparator with hysteresis which has a bias current circuit, a differential input stage, and an output stage is disclosed. The differential input stage uses an analog switch to connect the body of a field effect transistors to either a first voltage or a second voltage. The analog switch in the preferred embodiment is a double-throw switch.

Abstract: A circuit for limiting the output voltage from a power transistor connected in series with a resonant load between a voltage supply and a voltage reference, ground, is disclosed. The circuit includes a semiconductor junction element, in particular a diode of the SCR type, having an anode terminal connected to the voltage supply, a cathode terminal connected to a common circuit node between the power transistor and the resonant load, and a control terminal connected to a reference voltage of predetermined value. The reference voltage can be constructed by using a resistor connected in series with a diode across the voltage supply. The SCR diode is constructed using the parasitic PNP-NPN transistors which exist in the structure of the power transistor.

Abstract: The invention is used in a disk drive and comprises a feedforward circuit connected between the head position circuit and the speed control loop circuit. The feedforward circuit precompensates the speed control loop for changes in rotation drag due to movements in the head of a disk drive. The feedforward circuit may include one or more deadband amplifiers and may include filter circuit. The invention disclose the method for controlling the speed of a spindle motor in a disk drive which includes the step of precompensating the speed control loop circuit with a processed head positioning signal.

Abstract: A circuit for controlling the slew rate at a motor coil during turn-on in a commutation sequence is disclosed. The disclosed circuit includes a comparator for comparing the output of error amplifier to the input of the input buffer amplifier. The comparator connects the output of the error amplifier to the input of the buffer amplifier only after the input has been charged at a controlled rate. The integrating buffer amplifier includes an amplifier with a feedback capacitor, and a current source connected at its input, for reducing the voltage slew rate during turn-on of the transistor.

Abstract: A comparator with a built-in hysteresis is disclosed. The comparator has a differential input stage, an output stage, and a bias circuit with a hysteresis circuit. The hysteresis circuit selectively applies a bias voltage to the differential input stage to achieve the hysteresis.

Abstract: In a method for aligning a rotor of a polyphase dc motor in preparation for starting the motor. a first energization signal is applied to field coils of the motor in a first predetermined phase for a first predetermined time. Then, a second energization signal having a second predetermined phase displaced from the first phase by a predetermined amount is applied to the field coils for a second predetermined time period. In one embodiment, the second energization signal is applied to produce a maximum torque upon the rotor when the rotor is positioned at a location determined by the first energization signal. In the case of a three phase motor, the second energization signal is displaced by two commutations from the first energization signal.

Abstract: A circuit for clamping the voltage spike of a stator coil winding of a brushless direct current motor is disclosed. The circuit uses a comparator to monitor the voltage on a stator winding. When a voltage spike is detected, the comparator turns on the stator winding driver transistor to clamp the voltage spike. The comparator can be designed to trigger at a desired threshold voltage so that the threshold can optimized. Additionally, the comparator can be selectively disabled to trigger when voltage spikes are anticipated.

Abstract: A current limiting circuit used with voltage regulators or other similar circuits is disclosed. The current limiting circuit uses two transistors, configured as a differential pair, combined with a fixed current source to limit the current available to a pass transistor of the voltage regulator.

Abstract: A constant velocity head parking circuit is disclosed. The circuit includes a voice coil motor, a sense resistor, a park voltage source, and a feedback loop. The feedback loop includes a scaling circuit which can be constructed with an op amp and two resistors. The scaling circuit adds a voltage to the park voltage so that any voltage loses in the voice coil motor are compensated for.

Abstract: A circuit and method for operating a polyphase dc motor of the type having a plurality of driving coils connected together at a center tap current input node. Each driving coil have a current input node at an end opposite the center tap connection. A plurality of pairs of switches are arranged for connection in series across a power supply voltage. Each pair have a connection node between each switch connected to a respective one of the current input nodes. A sequencer individually operates the switches to cause a driving current to be passed between sequentially selected only single ones of the driving coils and the center tap current input node.

Abstract: A gate drive circuit which has an active voltage clamp is disclosed. The active voltage clamp protects the gate of a power transistor from an electrical over-stress condition. The active voltage clamp includes at least one zener diode connected in series with a current mirror.

Abstract: A method and circuit for providing a dual slew rate to a driver transistor. The method includes turning off a driver transistor at a programmable slew rate until a BEMF voltage spike is sensed, and then switching in a slower clamping slew rate. The slew rates are controlled by discharging a capacitor through a programmable discharge path until a voltage spike is detected and then through a clamping discharge path. The discharge paths include several transistors connected in series and control by digital logic.

Abstract: A method and circuit for implementing a frequency lock loop circuit in a disk drive is disclosed. The circuit includes the motor control elements of a direct current motor plus a coarse counter, a fine counter, and a digital to analog converter. The coarse counter is used to count down from a programmed coarse count. The fine counter begins to count down from a fine count when the coarse counter reaches zero. The count in the fine counter, when a zero crossing occurs, represents the difference between the expected period and the actual period and is loaded into a digital to analog converter which converts the difference to an analog voltage which is used by the coil drive circuit to either speed up or slow down the motor. The digital to analog conversion may be realized by a charge pump circuit.

Abstract: A switch circuit for a charge pump circuit is disclosed. The switch circuit has a first transistor for conducting current and is controlled by a second, third, and fourth transistor. The second transistor protects the first transistor for excessive gate-to-drain voltage. The third transistor receives the signal for switching the switch circuit and also serves as a cascoding transistor for protecting the fourth transistor from excessive gate-to-drain voltage. Consequently, the switch circuit can withstand high gate-to-drain voltages and has increased reliability. The switch also has a turn-off circuit to facilitate the depletion of charge on the control element of the first transistor. The switch circuit also has a zener diode to insure that excessive voltage is not applied across the gate-to drain of the first transistor.

Abstract: A circuit and method for generating a power-on reset signal with a designable hysteresis is disclosed. The circuit includes a low voltage stage, a high voltage stage, and a hysteresis stage. The low voltage stage includes a resistor in series with a current mirror. The high voltage stage includes a current mirror in series with a diode and two resistors. The hysteresis circuit includes a transistor connected across one of the two resistors. The method for generating the power-on reset signal includes the steps of sinking a power-on reset signal low when a voltage source reaches a first V.sub.be voltage threshold; driving the power-on reset signal high when the voltage source reaches a second threshold value; and providing hysteresis to the power-on reset signal.

Abstract: A method and apparatus for operating a polyphase dc motor selectively in dual-coil or uni-coil commutation modes. The motor has a plurality of "Y" connected driving coils connected together at a center tap. Each driving coil has an input node at an end opposite the center tap, and is driven by a switch pair. Each switch pair is arranged for connection in series across a power supply voltage, and has a node between each switch connected to a respective one of the coil input nodes. An additional pair of switches are provided for connection in series across the power supply with a connection node between each switch connected to the center tap. A circuit is provided to operate the switches to cause a driving current to be passed between sequentially selected pairs of the driving coils for an initial start-up time.