Data storage device calibrating parameter for heat assisted magnetic recording
View Patent ↗A data storage device is disclosed comprising a head actuated over a disk, wherein the head comprises a laser configured to heat the disk while writing data to the disk. A write power for the laser is calibrated, wherein the write power is applied to the laser while writing user data to the disk. A calibration power is applied to the laser for a first interval, wherein the calibration power is high enough to cause the head to contact the disk if applied for a second interval longer than the first interval. While applying the calibration power to the laser, test data is written to the disk during at least part of the first interval. The test data is read from the disk to generate a read signal, and a metric is generated based on the read signal.
1. A data storage device comprising:
a disk;
a head actuated over the disk, wherein the head comprises a laser configured to heat the disk while writing data to the disk; and
control circuitry configured to:
(a) calibrate a write power for the laser, wherein the write power is applied to the laser while writing user data to the disk;
(b) apply a calibration power to the laser for a first interval, wherein the calibration power is high enough to cause the head to contact the disk if applied for a second interval longer than the first interval;
(c) while applying the calibration power to the laser, write test data to the disk during at least part of the first interval; and
(d) read the test data from the disk to generate a read signal and generate a metric based on the read signal.
2. The data storage device as recited in claim 1 , wherein the data storage device further comprises a fly height actuator configured to actuate the head vertically over the disk, and the control circuitry is further configured to adjust a control signal applied to the fly height actuator based on the metric.
3. The data storage device as recited in claim 2 , wherein the control circuitry is further configured to generate the metric as the amplitude of the read signal after reading at least part of the test data.
4. The data storage device as recited in claim 3 , wherein the control circuitry is further configured to:
repeat blocks (b) through (d) for a plurality of different calibration powers; and
adjust the control signal applied to the fly height actuator based on a measured inflection point in the metrics generated for the different calibration powers.
5. The data storage device as recited in claim 4 , wherein the control circuitry is further configured to adjust the control signal applied to the fly height actuator based on a difference between the measured inflection point and a target inflection point.
6. The data storage device as recited in claim 5 , wherein the control circuitry is further configured to calibrate the target inflection point by:
calibrating a write setting for the control signal applied to the fly height actuator; and
while applying the write setting to the fly height actuator, repeating blocks (b) through (d) for a plurality of different calibration powers.
7. The data storage device as recited in claim 2 , wherein the control circuitry is further configured to adjust the write power for the laser based on the metric.
8. A method of operating a data storage device, the method comprising:
(a) calibrating a write power for a laser of a head, wherein the write power is applied to the laser while writing user data to a disk;
(b) applying a calibration power to the laser for a first interval, wherein the calibration power is high enough to cause the head to contact the disk if applied for a second interval longer than the first interval;
(c) while applying the calibration power to the laser, writing test data to the disk during at least part of the first interval; and
(d) reading the test data from the disk to generate a read signal and generate a metric based on the read signal.
9. The method as recited in claim 8 , further comprising adjusting a control signal applied to a fly height actuator based on the metric, wherein the fly height actuator is configured to actuate the head vertically over the disk.
10. The method as recited in claim 9 , further comprising generating the metric as the amplitude of the read signal after reading at least part of the test data.
11. The method as recited in claim 10 , further comprising:
repeating blocks (b) through (d) for a plurality of different calibration powers; and
adjusting the control signal applied to the fly height actuator based on a measured inflection point in the metrics generated for the different calibration powers.
12. The method as recited in claim 11 , further comprising adjusting the control signal applied to the fly height actuator based on a difference between the measured inflection point and a target inflection point.
13. The method as recited in claim 12 , further comprising calibrating the target inflection point by:
calibrating a write setting for the control signal applied to the fly height actuator; and
while applying the write setting to the fly height actuator, repeating blocks (b) through (d) for a plurality of different calibration powers.
14. The method as recited in claim 9 , further comprising adjusting the write power for the laser based on the metric.