Motor driver circuit for linear motor, positioning device using the same, and hard disk device

Abstract

Disclosed herein is a motor driver circuit including a logic circuit that generates a second code which changes linearly with a slope 'a' with respect to a first code based on a position command for a linear motor to be driven and that can switch the slope “a,” a D/A converter that converts the second code into an analog control signal, and a driver that drives the linear motor such that a current detection signal indicating a drive current of the linear motor approaches a target value that changes linearly with a slope “g” with respect to the control signal, the driver being configured to switch the slope “g.” The motor driver circuit is switchable between a first state in which g=gand a=aand a second state in which g=g(where |g|>|g|) and a=a=a×(g/g).