FUJITSU MPF3XXXAT - Manual (Page 60)

C141-E099-01EN 4 - 15
(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.