4.7 Servo Control

(1) Microprocessor unit (MPU)

The MPU executes startup of the spindle motor, movement to the reference cylinder, seek to the specified cylinder, and calibration operations.

The main internal operations of the MPU are shown below.

a.Spindle motor start

Starts the spindle motor and accelerates it to normal speed when power is applied.

b.Move head to reference cylinder

Drives the VCM to position the head at the any cylinder in the data area. The logical initial cylinder is at the outermost circumference (cylinder 0).

c.Seek to specified cylinder

Drives the VCM to position the head to the specified cylinder.

d.Calibration

Senses and stores the thermal offset between heads and the mechanical forces on the actuator, and stores the calibration value.

(2) Servo burst capture circuit

The servo burst capture circuit reproduces signals (position signals) that indicate the head position from the servo data on the data surface. From the servo area on the data area surface, via the data head, the burst signals of EVEN1, ODD, EVEN2 are output as shown in Figure 4.8 in subsequent to the servo mark, gray code that indicates the cylinder position, and index information. The servo signals do A/D-convert by Fourier-demodulator in the servo burst capture circuit. At that time the AGC circuit is in hold mode. The A/D converted data is recognized by the MPU as position information.

(3) D/A converter (DAC)

The control program calculates the specified data value (digital value) of the VCM drive current, and the value is converted from digital-to-analog so that an analog output voltage is sent to the power amplifier.

(4) Power amplifier

The power amplifier feeds currents, corresponding to the DAC output signal voltage to the VCM.

(5) Spindle motor control circuit

The spindle motor control circuit controls the sensor-less spindle motor. A spindle driver IC with a built-in PLL(FLL) circuit that is on a hardware unit controls the sensor-less spindle motor.

C141-E221

4-13

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Fujitsu MHV2080AS, MHV2060AS manual Microprocessor unit MPU, Servo burst capture circuit, A converter DAC, Power amplifier
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MHV2060AS, MHV2080AS, MHV2040AS specifications

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