Information storage device, write current adjustment method for the information storage device, and write control circuit
View Patent ↗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.
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.
2. 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.
3. 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.
4. 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.
5. 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.
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.
7. 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.
8. 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.
9. 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.
10. 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.
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.
12. 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.
13. 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.
14. 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.
15. 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.