Disk drive establishing write current limits prior to optimizing the write current for a plurality of tracks
A disk drive is disclosed comprising control circuitry operable to calibrate a write current parameter. A write current is initialized to an initial write current INIT_Iw, and an overshoot is initialized to a maximum MAX_OS. The write current is swept from INIT_Iw to a maximum write current MAX_Iw while writing and reading data from a target track to measure a first quality metric. A second quality metric associated with wide track erasure is also measured. A quality of the write operations is determined in response to the first and second quality metrics. When the quality of the write operations does not exceed a threshold, at least one of the MAX_Iw and MAX_OS is decreased and the process is repeated. Otherwise, the write current is swept from a minimum write current limit MAX_Iw to the adjusted MAX_Iw for a plurality of tracks to find an optimal write current for each track.
1. A disk drive comprising:
a disk comprising a plurality of tracks;
a head actuated over the disk; and
control circuitry operable to:
(a) set a maximum write current limit (MAX_Iw) and an maximum overshoot limit (MAX_OS);
(b) initialize a write current to an initial write current (INIT_Iw) less than MAX_Iw, and initialize an overshoot to MAX_OS;
(c) first sweep the write current from INIT_Iw to MAX_Iw, wherein for each write current:
write data to a target track; and
read the target track and measure a first quality metric;
(d) measure a second quality metric associated with wide track erasure;
(e) determine a quality of the write operations in response to the first and second quality metrics;
(f) when the quality of the write operations does not exceed a threshold, decrease at least one of MAX_Iw and MAX_OS and re-execute steps (b)-(e); and
(g) when the quality of the write operations exceeds the threshold, second sweep the write current from a minimum write current limit (MAX_Iw) to the adjusted MAX_Iw for a plurality of tracks to find an optimal write current for each track.
2. The disk drive as recited in claim 1 , wherein the data written to the target comprises pseudo random data.
3. The disk drive as recited in claim 1 , wherein the overshoot comprises an overshoot amplitude and an overshoot duration.
4. The disk drive as recited in claim 1 , wherein step (g) further comprises sweeping the overshoot from a minimum setting to the adjusted MAX_OS for the plurality of tracks to find an optimal overshoot for each track.
5. The disk drive as recited in claim 1 , wherein the control circuitry measures the quality of the write operation relative to a ratio between a maximum quality metric corresponding to MAX_Iw and a minimum quality metric generated over the first sweep.
6. The disk drive as recited in claim 1 , wherein the control circuitry selects MAX_Iw in step (g) relative to a ratio between a maximum quality metric corresponding to INIT_Iw and a minimum quality metric generated over the first sweep.
7. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to measure a second quality metric associated with wide track erasure in step (d) by:
writing data to at least five tracks on both sides of the target track; and
reading data from the target track and measure the second quality metric.
8. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to measure a second quality metric associated with wide track erasure in step (d) by:
reading data from at least five tracks on both sides of the target track;
measuring a second quality metric for each of the tracks; and
selecting one of the second quality metrics.
9. A method of operating a disk drive, the disk drive comprising a disk comprising a plurality of tracks, and a head actuated over the disk, the method comprising:
(a) setting a maximum write current limit (MAX_Iw) and an maximum overshoot limit (MAX_OS);
(b) initializing a write current to an initial write current (INIT_Iw) less than MAX_Iw, and initialize an overshoot to MAX_OS;
(c) first sweeping the write current from INIT_Iw to MAX_Iw, wherein for each write current:
write data to a target track; and
read the target track and measure a first quality metric;
(d) measuring a second quality metric associated with wide track erasure;
(e) determining a quality of the write operations in response to the first and second quality metrics;
(f) when the quality of the write operations does not exceed a threshold, decreasing at least one of MAX_Iw and MAX_OS and re-executing steps (b)-(e); and
(g) when the quality of the write operations exceeds the threshold, second sweeping the write current from a minimum write current limit (MAX_Iw) to the adjusted MAX_Iw for a plurality of tracks to find an optimal write current for each track.
10. The method as recited in claim 9 , wherein the data written to the target comprises pseudo random data.
11. The method as recited in claim 9 , wherein the overshoot comprises an overshoot amplitude and an overshoot duration.
12. The method as recited in claim 9 , wherein step (g) further comprises sweeping the overshoot from a minimum setting to the adjusted MAX_OS for the plurality of tracks to find an optimal overshoot for each track.
13. The method as recited in claim 9 , further comprising measuring the quality of the write operation relative to a ratio between a maximum quality metric corresponding to MAX_Iw and a minimum quality metric generated over the first sweep.
14. The method as recited in claim 9 , further comprising selecting the MAX_Iw in step (g) relative to a ratio between a maximum quality metric corresponding to INIT_Iw and a minimum quality metric generated over the first sweep.
15. The method as recited in claim 9 , further comprising measuring a second quality metric associated with wide track erasure in step (d) by:
writing data to at least five tracks on both sides of the target track; and
reading data from the target track and measure the second quality metric.
16. The method as recited in claim 9 , further comprising measuring a second quality metric associated with wide track erasure in step (d) by:
reading data from at least five tracks on both sides of the target track;
measuring a second quality metric for each of the tracks; and
selecting one of the second quality metrics.