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7 servo control, 1 servo control circuit – FUJITSU MPG3XXXAH-E User Manual

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C141-E116-01EN

4 - 13

4.7

Servo Control

The actuator motor and the spindle motor are submitted to servo control. The actuator motor is
controlled for moving and positioning the head to the track containing the desired data. To turn
the disk at a constant velocity, the actuator motor is controlled according to the servo data that is
written on the data side beforehand.

4.7.1

Servo control circuit

Figure 4.4 is the block diagram of the servo control circuit. The following describes the functions
of the blocks:

(5)

(1)

(2)

(3)

(4)

P.
Amp.

CSR: Current Sense Resistor
VCM: Voice Coil Motor

Spindle
motor
control

DSP
unit

Servo
burst
capture

SVC

MPU

CSR

Driver

DAC

ADC

Position Sense

Head

VCM current

VCM

Spindle
motor

(7)

(6)

Figure 4.4

Block diagram of servo control circuit

(1)

Microprocessor unit (MPU)

The MPU includes DSP unit, etc., and the MPU starts the spindle motor, moves the heads to the
reference cylinders, seeks the specified cylinder, and executes calibration according to the internal
operations of the MPU.

The major internal operations are listed below.

a.

Spindle motor start

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