# US 7,609,470 B2 · Information storage device, write current adjustment method for the information storage device, and write control circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,470 B2 - Document ID: US7609470B2 - Status: Granted - Kind: B2 - Application number: 11/452,841 - Filed: 2006-06-14 - Published: 2007-09-13 - Granted: 2009-10-27 - Earliest claimed: 2006-03-10 - Assignees: Fujitsu Limited - Inventors: Yuichiro Yamazaki - Web page: https://patentgrep.com/patent/US7609470B2 ## CPC - G11B 5/09: Digital recording - G11B 27/36: Monitoring, i.e. supervising the progress of recording or reproducing {(for digital recording G11B20/00 and s.gr.; for monitoring, testing or measuring of TV recorders of the type covered by H04N5/76 and subgroups, see H04N17/06)} - G11B 2220/2516: Hard disks - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract There is provided a magnetic disk device or the like which is capable of improving signal quality by suppressing occurrence of erasure of adjacent tracks due to spreading of a writing spot. The magnetic disk device is capable of controlling a steady state value of a write current for writing into a magnetic disk, an overshoot value, or a width thereof. The magnetic disk device comprises a VMM measurement section that measures a VMM, and a write current setting section that sets the write current, based on a value of the VMM measured by the VMM measurement section, such that a data writing spot is prevented from spreading during writing into the medium and occurrence of side erasure is prevented. ## Claims ### Claim 1 An information storage device having a recording medium and a head to write information into the recording medium, and controlling a steady state value, an overshoot value or an overshoot width of a write current for writing into the recording medium, the device comprising: a Viterbi Metric Margin measurement section to measure a Viterbi Metric Margin; and a write current setting section to set the write current, based on a value of the Viterbi Metric Margin measured by the Viterbi Metric Margin measurement section, such that a data writing spot is prevented from spreading during writing into the medium and occurrence of side erasure is prevented; wherein the Viterbi Metric Margin measurement section further measures a value of a lead Viterbi Metric Margin at the beginning of writing into the recording medium, and the write current setting section sets the write current so as to prevent deterioration in signal quality at the beginning of writing, based on the measured value of the lead Viterbi Metric Margin. ### Claim 2 (depends on 1) The information storage device according to claim 1, wherein the write current setting section sets any one of the steady state current, the overshoot value, or the overshoot width to be adjusted as the write current. ### Claim 3 (depends on 1) The information storage device according to claim 1, further comprising a side erasure occurrence prediction section to predict occurrence or nonoccurrence of side erasure by use of actually measured values measured by the Viterbi Metric Margin measurement section with respect to at least two numbers of times of writing, wherein the write current setting section sets the write current, based on a predicted value predicted by the side erasure occurrence prediction section. ### Claim 4 (depends on 3) The information storage device according to claim 3, wherein the side erasure occurrence prediction section predicts, by linear interpolation, the occurrence or nonoccurrence of side erasure with respect to a tolerance value of side erasure. ### Claim 5 (depends on 1) The information storage device according to claim 1, further comprising a write precompensation value adjustment section that adjusts a write precompensation value as a parameter of a write system, wherein the Viterbi Metric Margin measurement section measures the Viterbi Metric Margin with respect to a setting value of the write current adjusted by the write precompensation value adjustment section. ### Claim 6 A write current adjustment method for an information storage device controlling a steady state value, an overshoot value, or an overshoot width of a write current for writing into a recording medium, the method comprising: measuring a Viterbi Metric Margin; and setting the write current, based on a value of the measured Viterbi Metric Margin, such that a data writing spot is prevented from spreading during writing into the medium and occurrence of side erasure is prevented; wherein the measuring measures a value of a lead Viterbi Metric Margin at the beginning of writing into the recording medium, and the setting sets the write current so as to prevent deterioration in signal quality at the beginning of writing, based on the measured value of the lead Viterbi Metric Margin. ### Claim 7 (depends on 6) The write current adjustment method for an information storage device, according to claim 6, wherein the setting sets any one of the steady state current, the overshoot value, or the overshoot width to be adjusted as the write current. ### Claim 8 (depends on 6) The write current adjustment method for an information storage device according to claim 6, further comprising adjusting a write precompensation value as a parameter of a write system, wherein the measuring measures the Viterbi Metric Margin with respect to a setting value of the write current adjusted by the adjusting. ### Claim 9 (depends on 6) The write current adjustment method for an information storage device, according to claim 6, further comprising predicting occurrence or nonoccurrence of side erasure by use of actually measured values measured by the measuring with respect to at least two numbers of times of writing, wherein the setting sets the write current, based on a predicted value predicted by the predicting. ### Claim 10 (depends on 9) The write current adjustment method for an information storage device, according to claim 9, wherein the predicting predicts, by linear interpolation, the occurrence or nonoccurrence of side erasure with respect to a tolerance value of side erasure. ### Claim 11 A write control circuit controlling a steady state value, an overshoot value, or an overshoot width of a write current for writing into a recording medium, the circuit comprising: a Viterbi Metric Margin measurement section to measure a Viterbi Metric Margin; and a write current setting section to set the write current, based on a value of the Viterbi Metric Margin measured by the Viterbi Metric Margin measurement section, such that a data writing spot is prevented from spreading during writing into the medium and occurrence of side erasure is prevented; wherein the Viterbi Metric Margin measurement section further measures a value of a lead Viterbi Metric Margin at the beginning of writing into the recording medium, and the write current setting section sets the write current so as to prevent deterioration in signal quality at the beginning of writing, based on the measured value of the lead Viterbi Metric Margin. ### Claim 12 (depends on 11) The write control circuit according to claim 11, wherein the write current setting section sets any one of the steady state current, the overshoot value, or the overshoot width to be adjusted as the write current. ### Claim 13 (depends on 11) The write control circuit according to claim 11, further comprising a side erasure occurrence prediction section to predict occurrence or nonoccurrence of side erasure by use of actually measured values measured by the Viterbi Metric Margin measurement section with respect to at least two numbers of times of writing, wherein the write current setting section sets the write current, based on a predicted value predicted by the side erasure occurrence prediction section. ### Claim 14 (depends on 13) The write control circuit according to claim 13, wherein the side erasure occurrence prediction section predicts, by linear interpolation, the occurrence or nonoccurrence of side erasure with respect to a tolerance value of side erasure. ### Claim 15 (depends on 11) The write control circuit according to claim 11, further comprising a write precompensation value adjustment section that adjusts a write precompensation value as a parameter of a write system, wherein the Viterbi Metric Margin measurement section measures the Viterbi Metric Margin with respect to a setting value of the write current adjusted by the write precompensation value adjustment section.