Disk drive calibrating preamp for servo sectors and data sectors

1. A disk drive comprising:

a disk comprising a plurality of tracks defined by servo sectors, wherein each track comprises a plurality of data sectors;

a head actuated over the disk;

a preamp circuit operable to amplify a read signal emanating from the head to generate a pre-amplified read signal; and

control circuitry comprising a variable gain amplifier (VGA) operable to amplify the pre-amplified read signal to generate an amplified read signal, the control circuitry operable to:

calibrate a first gain setting of the preamp circuit in response to a plurality of the servo sectors;

adjust the first gain setting in response to a plurality of the data sectors;

adjust a second gain setting of the VGA in order to adjust an amplitude of the amplified read signal based on a target response;

calibrate the first gain setting of the preamp circuit in response to the second gain setting;

wherein:

the control circuitry is operable to calibrate the first gain setting in response to the servo sectors by:

increasing the first gain setting when the second gain setting is greater than a servo maximum threshold; and

decreasing the first gain setting when the second gain setting is less than a servo minimum threshold,

the control circuitry is operable to adjust the first gain setting in response to the data sectors by:

increasing the first gain setting when the second gain setting is greater than a data maximum threshold; and

decreasing the first gain setting when the second gain setting is less than a data minimum threshold; and

a range defined by the data maximum threshold and the data minimum threshold is wider than a range defined by the servo maximum threshold and the servo minimum threshold.

2. The disk drive as recited in claim 1 , wherein the control circuitry further comprises a cut-off filter for filtering the amplified read signal output by the VGA when reading the servo sectors, and after adjusting the first gain setting in response to the data sectors, the control circuitry is operable to adjust the cut-off filter when the second gain setting while reading the servo sectors is outside a range.

3. The disk drive as recited in claim 2 , wherein the control circuitry is operable to adjust at least one of a bandwidth and gain of the cut-off filter when the second gain setting is outside the range.

4. The disk drive as recited in claim 1 , wherein prior to adjusting the first gain setting in response to the data sectors, the control circuitry is operable to adjust a fly height of the head.

5. The disk drive as recited in claim 4 , wherein the control circuitry is operable to adjust the fly height of the head by:

adjusting a fly height control signal until the head contacts the disk; and

selecting an operating fly height in response to the head contacting the disk.

6. A method of operating a disk drive comprising a disk including a plurality of tracks defined by servo sectors, wherein each track comprises a plurality of data sectors, a head actuated over the disk, a preamp circuit operable to amplify a read signal emanating from the head to generate a pre-amplified read signal, and a variable gain amplifier (VGA) operable to amplify the pre-amplified read signal to generate an amplified read signal, the method comprising:

calibrating a first gain setting of the preamp circuit in response to a plurality of the servo sectors;

adjusting the first gain setting in response to a plurality of the data sectors;

adjusting a second gain setting of the VGA in order to adjust an amplitude of the amplified read signal based on a target response; and

calibrating the first gain setting of the preamp circuit in response to the second gain setting,

wherein:

calibrating the first gain setting in response to the servo sectors comprises:

increasing the first gain setting when the second gain setting is greater than a servo maximum threshold; and

decreasing the first gain setting when the second gain setting is less than a servo minimum threshold;

adjusting the first gain setting in response to the data sectors comprises:

increasing the first gain setting when the second gain setting is greater than a data maximum threshold; and

decreasing the first gain setting when the second gain setting is less than a data minimum threshold; and

a range defined by the data maximum threshold and the data minimum threshold is wider than a range defined by the servo maximum threshold and the servo minimum threshold.

7. The method as recited in claim 6 , wherein the disk drive further comprises a cut-off filter for filtering the amplified read signal output by the VGA when reading the servo sectors, and after adjusting the first gain setting in response to the data sectors, the method further comprising adjusting the cut-off filter when the second gain setting while reading the servo sectors is outside a range.

8. The method as recited in claim 7 , further comprising adjusting at least one of a bandwidth and gain of the cut-off filter when the second gain setting is outside the range.

9. The method as recited in claim 6 , wherein prior to adjusting the first gain setting in response to the data sectors, further comprising adjusting a fly height of the head.

10. The method as recited in claim 9 , wherein adjusting the fly height of the head comprises:

adjusting a fly height control signal until the head contacts the disk; and

selecting an operating fly height in response to the head contacting the disk.

11. A disk drive comprising:

a disk comprising a plurality of tracks defined by servo sectors, wherein each track comprises a plurality of data sectors;

a head actuated over the disk;

a preamp circuit operable to amplify a read signal emanating from the head to generate a pre-amplified read signal; and

control circuitry comprising a variable gain amplifier (VGA) operable to amplify the pre-amplified read signal to generate an amplified read signal, and a cut-off filter for filtering the amplified read signal output by the VGA when reading the servo sectors, the control circuitry operable to:

calibrate a first gain setting of the preamp circuit in response to a plurality of the servo sectors;

adjust the first gain setting in response to a plurality of the data sectors;

adjust a second gain setting of the VGA in order to adjust an amplitude of the amplified read signal based on a target response; and

after adjusting the first gain setting in response to the data sectors, adjust the cut-off filter when the second gain setting while reading the servo sectors is outside a range.

12. A method of operating a disk drive, the disk drive comprising a disk comprising a plurality of tracks defined by servo sectors, wherein each track comprises a plurality of data sectors, a head actuated over the disk, a preamp circuit operable to amplify a read signal emanating from the head to generate a pre-amplified read signal, and control circuitry comprising a variable gain amplifier (VGA) operable to amplify the pre-amplified read signal to generate an amplified read signal, and a cut-off filter for filtering the amplified read signal output by the VGA when reading the servo sectors, the method comprising:

calibrating a first gain setting of the preamp circuit in response to a plurality of the servo sectors;

adjusting the first gain setting in response to a plurality of the data sectors;

adjust a second gain setting of the VGA in order to adjust an amplitude of the amplified read signal based on a target response; and

after adjusting the first gain setting in response to the data sectors, adjusting the cut-off filter when the second gain setting while reading the servo sectors is outside a range.

13. A disk drive comprising:

a disk comprising a plurality of tracks defined by servo sectors, wherein each track comprises a plurality of data sectors;

a head actuated over the disk;

a preamp circuit operable to amplify a read signal emanating from the head to generate a pre-amplified read signal; and

control circuitry operable to:

calibrate a first gain setting of the preamp circuit in response to a plurality of the servo sectors; and

adjust the first gain setting in response to a plurality of the data sectors;

wherein prior to adjusting the first gain setting in response to the data sectors, the control circuitry is operable to adjust a fly height of the head.

14. The disk drive as recited in claim 13 , wherein the control circuitry is operable to adjust the fly height of the head by:

adjusting a fly height control signal until the head contacts the disk; and

selecting an operating fly height in response to the head contacting the disk.

15. A method of operating a disk drive comprising a disk including a plurality of tracks defined by servo sectors, wherein each track comprises a plurality of data sectors, a head actuated over the disk, and a preamp circuit operable to amplify a read signal emanating from the head to generate a pre-amplified read signal, the method comprising:

calibrating a first gain setting of the preamp circuit in response to a plurality of the servo sectors; and

adjusting the first gain setting in response to a plurality of the data sectors;

wherein prior to adjusting the first gain setting in response to the data sectors, further comprising adjusting a fly height of the head.

16. The method as recited in claim 15 , wherein adjusting the fly height of the head comprises:

adjusting a fly height control signal until the head contacts the disk; and

selecting an operating fly height in response to the head contacting the disk.