Data-Surface Servo Format - Fujitsu MPG3409AT Product Manual

(4) D/A converter (DAC)
The D/A converter (DAC) converts the VCM drive current value (digital value) calculated by the
DSP unit into analog values and transfers them to the power amplifier.
(5) Power amplifier
The power amplifier feeds currents, corresponding to the DAC output signal voltage to the VCM.
(6) Spindle motor control circuit
The spindle motor control circuit controls the sensor-less spindle motor. This circuit detects
number of revolution of the motor by the interrupt generated periodically, compares with the target
revolution speed, then flows the current into the motor coil according to the differentiation
(aberration).
(7) Driver circuit
The driver circuit is a power amplitude circuit that receives signals from the spindle motor control
circuit and feeds currents to the spindle motor.
(8) VCM current sense resistor (CSR)
This resistor controls current at the power amplifier by converting the VCM current into voltage
and feeding back.
4.7.2

Data-surface servo format

Figure 4.5 describes the physical layout of the servo frame. The three areas indicated by (1) to (3)
in Figure 4.5 are described below.
(1) Inner guard band
The head is in contact with the disk in this space when the spindle starts turning or stops, and the
rotational speed of the spindle can be controlled on this cylinder area for head moving.
(2) Data area
This area is used as the user data area and SA area.
(3) Outer guard band
This area is located at outer position of the user data area, and the rotational speed of the spindle
can be controlled on this cylinder area for head moving.
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