Patent ID: 7902778

Claim:
In an integrated circuit, retract circuitry for controlling application of power from a capacitor to a voice coil motor in a disk drive, comprising: a retract transistor, having a control terminal and having a conduction path for coupling between the capacitor and a first side of the voice coil motor; and; drive circuitry coupled to the control terminal of the retract transistor, for turning on the retract transistor in a retract stage; a low side transistor, having a conduction path for coupling between a second side of the voice coil motor and a ground voltage, and having a control terminal; a low side amplifier, having an output coupled to the conduction path of the low side transistor, and having first and second inputs, the first input for coupling to the second side of the voice coil motor; a resistor in the integrated circuit, for coupling between the first side of the voice coil motor and the second input of the low side amplifier; and a current control circuit, coupled to the second input of the low side amplifier, for conducting a selected current, wherein the current control circuit is operative even after loss of a main power supply.