Patents by Inventor Sassan Mortazavi

Patent number: 5838515
Abstract: A voice coil motor (VCM) driver has four field effect transistors connected to a motor coil as an H-bridge. A sense resistor in series with the coil and the H-bridge senses coil current. A feedback amplifier provides a feedback signal from a voltage developed across the sense resistor. A summing junction sums current command signals with the feedback signal. A transconductance loop compensation amplifier has an inverting input connected to the summing junction, has a non-inverting input connected to a reference level, and has an output control signal node. The control level is connected to control linear transconductance differential driver amplifiers including the four field effect transistors during a linear drive mode.
Type: Grant
Filed: April 30, 1996
Date of Patent: November 17, 1998
Assignee: Quantum Corporation
Inventors: Sassan Mortazavi, Mehran Ataee
Patent number: 5737144
Abstract: A voltage boost circuit within a hard disk drive is realized by switching a center tap node of a three phase spindle motor to ground during a power down sequence, thereby employing inductance of the spindle motor as a voltage boost inductor. The boosted voltage is rectified and stored in a capacitor for use, e.g. to control a source transistor of an actuator driver during an actuator retract operation.
Type: Grant
Filed: June 5, 1996
Date of Patent: April 7, 1998
Assignee: Quantum Corporation
Inventors: Mehran Ataee, Sassan Mortazavi
Patent number: 4849835
Abstract: A technique and associated arrangement for detecting loss of phase/frequency lock in a phase lock loop, particularly for a magnetic disk drive servo system the phase lock loop detects timing asynchronism and loss of lock.
Type: Grant
Filed: March 19, 1987
Date of Patent: July 18, 1989
Assignee: Unisys Corporation
Inventors: Seyed Entezarmahdi, Sassan Mortazavi