Data storage device screening heads by verifying defects after defect scan

• US 9,117,489 B1
• Filed: 02/18/2014
• Issued: 08/25/2015
• Est. Priority Date: 02/18/2014
• Status: Active Grant

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Dang, Dean V., Tsai, Chun Sei, Patel, Chirag C., Barlow, Carl E., Banh, Thao Hieu, Zayed, Ammar A.
• Primary Examiner(s): Mercedes, Dismery
• Application Number:
  US14/182,965
• Time in Patent Office: 553 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G11B 20/1889 with discs
• CPC Class Codes: G11B 2220/20 Disc-shaped record carriers
• CPC Class Codes: 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
• CPC Class Codes: G11B 5/09 Digital recording
• CPC Class Codes: G11B 5/59688 Servo signal format patterns or signal processing thereof, e.g. dual, tri, quad, burst signal patterns

Abstract

A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of tracks. A defect scan of at least one of the tracks is executed, and a log entry is generated when a defect is detected. After the defect scan, a verify operation is executed for at least two of the detected defects. A number of times the verify operation detects a false defect is counted, and whether the head is defective is determined based at least partly on the count.

Claims

1. A data storage device comprising:

a disk comprising a plurality of tracks;

a head; and

control circuitry configured to;

defect scan at least one of the tracks and generate a log entry when a defect is detected;

after the defect scan, execute a verify operation for at least two of the detected defects;

count a number of times the verify operation detects a false defect; and

determine whether the head is defective based at least partly on the count.

2. The data storage device as recited in claim 1, wherein the control circuitry is further configured to generate the log entry when a target defect type is detected.

3. The data storage device as recited in claim 2, wherein the count corresponds to a number of times the target defect type is falsely detected.

4. The data storage device as recited in claim 3, wherein the target defect type comprises a drop-in defect.

5. The data storage device as recited in claim 3, wherein the control circuitry is further configured to determine whether the head is defective based on a total number of log entries generated during the defect scan.

6. The data storage device as recited in claim 5, wherein the control circuitry is further configured to determine the head is defective when the total number of log entries exceeds a threshold.

7. The data storage device as recited in claim 5, wherein the control circuitry is further configured to determine the head is defective when the total number of log entries corresponding to a target defect type exceeds a threshold.

8. The data storage device as recited in claim 7, wherein the target defect type comprises a drop-in defect.

9. A method of operating a data storage device, the method comprising:

defect scanning at least one track of a disk and generating a log entry when a defect is detected;

after the defect scan, executing a verify operation for at least two of the detected defects;

counting a number of times the verify operation detects a false defect; and

determining whether a head is defective based at least partly on the count.

10. The method as recited in claim 9, further comprising generating the log entry when a target defect type is detected.

11. The method as recited in claim 10, wherein the count corresponds to a number of times the target defect type is falsely detected.

12. The method as recited in claim 11, wherein the target defect type comprises a drop-in defect.

13. The method as recited in claim 11, further comprising determining whether the head is defective based on a total number of log entries generated during the defect scan.

14. The method as recited in claim 13, further comprising determining the head is defective when the total number of log entries exceeds a threshold.

15. The method as recited in claim 13, further comprising determining the head is defective when the total number of log entries corresponding to a target defect type exceeds a threshold.

16. The method as recited in claim 15, wherein the target defect type comprises a drop-in defect.