Servo Control; Figure 4.7 Block Diagram Of Servo Control Circuit - Fujitsu MHM2100AT - Mobile 10 GB Hard Drive Product Manual

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 4.7 is the block diagram of the servo control circuit. The following
describes the functions of the blocks:
(1)
(2)
Servo
Head
burst
capture
Position Sense
CSR: Current Sense Resister
VCM: Voice Coil Motor

Figure 4.7 Block diagram of servo control circuit

(1) Microprocessor unit (MPU)
The MPU includes the DSP unit, 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. Main internal
operation of the MPU are shown below.
C141-E104-03EN
MPU
(3)
DAC
DSP
unit
(5)
Spindle
motor
control
4.6 Read/write Circuit
SVC
(4)
Power VCM current
Amp
CSR
(7)
VCM
(6)
Spindle
Driver
motor
4-15