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C141-E077-01EN4 - 14
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
DACADC
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.