Disk drive multiplexing read signal and fly height signal to a transmission line
View Patent ↗A disk drive is disclosed comprising a disk comprising a plurality of servo tracks defined by servo sectors, and a head actuated over the disk, wherein the head comprises a read element operable to generate a read signal. The disk drive further comprises a fly height sensor operable to generate a fly height signal for the head, and control circuitry comprising a multiplexer operable to multiplex the read signal and the fly height signal to a transmission line. The multiplexer is configured to select the read signal when reading the servo sectors of a servo track, and configured to select the fly height signal when reading a segment of the servo track between consecutive servo sectors.
1. A disk drive comprising:
a disk comprising a plurality of servo tracks defined by servo sectors;
a head actuated over the disk, the head comprising a read element configured to generate a read signal;
a fly height sensor configured to generate a fly height signal for the head; and
control circuitry comprising a multiplexer configured to multiplex the read signal and the fly height signal to a first transmission line, the control circuitry configured to:
configure the multiplexer to select the read signal when reading the servo sectors of a servo track; and
configure the multiplexer to select the fly height signal when reading a segment of the servo track between consecutive servo sectors.
2. The disk drive as recited in claim 1 , wherein the control circuitry comprises:
a preamp circuit comprising the multiplexer; and
a read channel circuit coupled to the first transmission line.
3. The disk drive as recited in claim 2 , wherein the read channel comprises:
a sampling device configured to sample the read signal when reading the servo sectors and configured to sample the fly height signal when reading the segment of the servo track; and
a buffer configured to buffer signal samples generated by the sampling device.
4. The disk drive as recited in claim 2 , wherein the preamp comprises:
a touchdown detector configured to detect a touchdown event in response to the fly height signal; and
a second transmission line configured to transmit the touchdown event to the read channel.
5. The disk drive as recited in claim 1 , wherein the control circuitry is further configured to detect a defect on the disk in response to the fly height signal.
6. The disk drive as recited in claim 5 , wherein the control circuitry is further configured to detect the defect on the disk by detecting a slope of the fly height signal.
7. The disk drive as recited in claim 5 , wherein the control circuitry is further configured to detect the defect on the disk by comparing the fly height signal to a threshold.
8. The disk drive as recited in claim 5 , wherein the control circuitry is further configured to detect the defect on the disk by correlating the fly height signal with a defect signal representing a defect type.
9. The disk drive as recited in claim 8 , wherein the defect type comprises a thermal asperity.
10. The disk drive as recited in claim 1 , wherein the fly height sensor comprises a touchdown sensor.
11. The disk drive as recited in claim 10 , wherein the touchdown sensor comprises a magnetoresistive element.
12. A method of operating a disk drive, the disk drive comprising a disk comprising a plurality of servo tracks defined by servo sectors, a head actuated over the disk, the head comprising a read element configured to generate a read signal, a fly height sensor configured to generate a fly height signal for the head, and a multiplexer configured to multiplex the read signal and the fly height signal to a transmission line, the method comprising:
configuring the multiplexer to select the read signal when reading the servo sectors of a servo track; and
configuring the multiplexer to select the fly height signal when reading a segment of the servo track between consecutive servo sectors.
13. The method as recited in claim 12 , further comprising:
sampling the read signal when reading the servo sectors and sampling the fly height signal when reading the segment of the servo track; and
buffering the signal samples generated by sampling the read signal and the fly height signal.
14. The method as recited in claim 12 , further comprising detecting a defect on the disk in response to the fly height signal.
15. The method as recited in claim 14 , further comprising detecting the defect on the disk by detecting a slope of the fly height signal.
16. The method as recited in claim 14 , further comprising detecting the defect on the disk by comparing the fly height signal to a threshold.
17. The method as recited in claim 14 , further comprising detecting the defect on the disk by correlating the fly height signal with a defect signal representing a defect type.
18. The method as recited in claim 17 , wherein the defect type comprises a thermal asperity.
19. The method as recited in claim 12 , further comprising detecting a touchdown event in response to the fly height signal, wherein the touchdown event is detected when the head contacts the disk.