Servo Format - Fujitsu MAH3091MC - Enterprise 9.1 GB Hard Drive Product/Maintenance Manual

(3) SPM/VCM driver
The power amp drive signal output by the DSP (digital signal processor) is converted to a current
for driving the VCM.
This consists of a controller which controls the sensor-less spindle motor by detecting the counter
electro-motive voltage and a power MOSFET which drives the spindle motor. (MAH series,
MAJ3182 series and MAJ3091 series contain a power transistor inside the SPM/VCM combo.)
8.7.2

Servo format

(1) Zone format
The voice coil motor is controlled to position a data head over a target cylinder, using the servo
data that has already been recorded on the data surface. Figure 8.5 shows zone format.
1) Dead space
The dead space is at the innermost position of a disk. At spindle start and stop, the head is in
contact with this area of the disk.
2) Inner guard band (IGB)
IGB is located in an inner position of a disk. IGB is used to detect that actuator operation has
exceeded the ordinary seek operation range.
3) Data zone
The servo zone is the data recording part on the data side. Ordinary head seek operations are
done within this zone.
4) Outer guard band (OGB)
OGB is located in an outer position of a disk. Like IGB, OGB is also used to detect that
actuator operation has exceeded the ordinary seek operation range.
(2) Frame format
The servo pattern consists of 108 servo frames for MAH series, or 84 servo frames for MAJ series
per one revolution. One servo frame is divided into 4 areas and these areas are separated with a
gap. Figure 8.6 shows the servo frame configuration.
1) Training area
The training area consists of a fixed-period burst signal and has following functions.
C141-E103-02EN 8 - 11