Patent ID: 6934110

Claim:
An apparatus to generate an adaptive track zero crossing signal in a disc drive, the apparatus comprising: an adder adding and outputting a predetermined signal to generate a track zero crossing signal and a correction signal; a comparator having a first input node and a second input node, receiving the predetermined signal from the adder through the first input node, receiving a reference voltage signal through the second input node, comparing the signals input into the first and second input nodes, and generating a track zero crossing signal having a square wave; and an offset correction calculator measuring lengths of high and low sections of the track zero crossing signal, calculating a ratio of differences in the lengths between the high and low sections, and generating a correction signal to maintain a duty ratio of the track zero crossing signal at a predetermined target value using the calculated ratio, wherein the offset correction calculator includes: a counting unit measuring time periods of the high and low sections for each cycle of the track zero crossing signal and outputting the measured time periods; and a operator generating a predetermined calculation signal corresponding to a difference ratio in time periods between the high and low sections using the measured time periods of the high and low sections, and wherein the predetermined difference ratio is calculated by the formula M =( N 2 − N 1 )/( N 2 + N 1 ), where N 1 is a time period of the high section of the track zero crossing signal, and N 2 is a time period of the low section of the track zero crossing signal.