Patent ID: 6373650
Filing Date: 2002-04-16
Classification: G11B

Abstract:
A disc drive including a voice coil driver circuit comprising:at least one disc; a spindle motor driver; a spindle motor mechanically coupled to the disc and causing the disc to rotate or not rotate in response to signals from the spindle motor driver; a control logic unit electrically coupled to the spindle motor driver and supplying control signals thereto; a voice coil motor; at least one head coupled to the voice coil motor, the head reading and writing data to and from the disc; and a voice coil motor driver having inputs coupled to the control logic unit and having outputs coupled to the voice coil motor, the voice coil motor driver supplying electrical signals to the voice coil motor, the voice coil motor driver comprising: a pair of power amplifiers having a common input terminal and equal gain magnitudes but opposite gain sign, a first of the pair having an output coupled to a first terminal of the voice coil motor and a second of the pair having an output coupled to a second terminal of the voice coil motor; a current sensing resistor coupled in series with the voice coil motor; a first operational amplifier having a first input coupled to a first terminal of the current sensing resistor and a second input coupled to a second terminal of the current sensing resistor, the first operational amplifier having a first gain; a first switch having a first terminal coupled to an output of the first operational amplifier; a second operational amplifier having an inverting input coupled to the first terminal of the first switch, a noninverting input coupled to a reference voltage and an output coupled to a second terminal of the first switch; a third operational amplifier having an input coupled to the second terminal of the first switch and an output coupled to the common input of the pair of power amplifiers; a second switch, the second switch having a first terminal coupled to the output of the second operational amplifier and a second terminal coupled to the inverting input of the third operational amplifier, an open circuit being formed between the first and second terminals of the second switch in the normal mode of operation and a short circuit being formed between the first and second terminals of the second switch in the head parking or unparking modes of operation; and a controller coupled to the first switch such that, when in a normal mode of operation, the output of the first operational amplifier is coupled to the input of the third operational amplifier, and, when in a head-parking or head-unparking mode of operation, the output of the first operational amplifier is coupled to an input of the second operational amplifier and an output of the second operational amplifier is coupled to the input to the third operational amplifier.