Abstract: A controller for controlling the voltage slew-rate of an inductive load connected to the drain of a field effect transistor is disclosed. The controller includes a current generator electrically connected between the gate and the drain of the field effect transistor, the current generator providing a current at the gate of the field effect transistor to offset a feed back current at the gate of the transistor due to gate-drain capacitance of the transistor. The current generator includes capacitor means having one end electrically connected to the drain of the field effect transistor, a current multiplier electrically connected between another end of the capacitor means and the gate of the field effect transistor, and a current source electrically connected to the gate of the field effect transistor. The current multiplier includes at least one current mirror, and the current source includes a constant current source.

Abstract: A frequency detector for a PLL controller, the controller being for generating an output signal to control a motor driver electrically connected to a motor having multiple phase windings arranged as a stator and a rotor having a permanent magnet or a DC current excitation winding for rotating the rotor, the motor driver selectively establishing current paths through selected windings in response to said output signal, to provide maximum torque to the rotor based on the rotational position of the rotor relative to the windings, the frequency detector comprising a monitor for detecting a number of pulses in said output signal during a time period between a first and a second rotational position of the rotor relative to the windings and a governor for generating a frequency control signal as a function of said number of pulses, wherein the PLL controller generates said output signal at output frequencies selectively as a function of said frequency control signal, whereby the frequency detector minimizes a differ

Abstract: A hysteresis circuit for providing hysteresis for a degree of noise immunity when detecting zero-crossings of a hard disk drive. A comparator is used to detect the zero-crossings associated with one of the windings of the disk drive's spindle motor. When a zero-crossing is detected, the hysteresis circuit introduces a hysteresis voltage to one of the inputs to the comparator. A positive hysteresis voltage is applied when the slope of the back emf signal corresponding to the motor winding is negative. Conversely, a negative hysteresis voltage is applied when the back emf signal has a positive slope. The slope of the back emf signal is determined by a logic combination of the commutation signals used to commutate the spindle motor.

Abstract: A circuit for reducing or eliminating the sensitivity of alarm circuitry to false alarms caused by noise occurring synchronously with a 60 Hz line voltage. The 60 Hz line signal is applied to a variable-threshold circuit which produces a 60 Hz clock signal. The clock signal produced by the variable-threshold circuit may be selected to occur at different points during a cycle of the 60 Hz line signal. In response to successive alarm signals, the clock signal produced by the variable-threshold circuit occurs with different phasing relationships to the 60 Hz line signal. Before an alarm indication is made, an alarm signal must be provided by the smoke sensor in response to a plurality of successive samples.