4.7 Servo Control
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 signal of SERVO A, SERVO B, SERVO C, and SERVO D is output as shown in Figure 4.9 in subsequent to the servo mark, gray code that indicates the cylinder position, and index information. The servo signals do
(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
(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
(6) 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.
(7) VCM current sense resistor (CSR)
This resistor controls current at the power amplifier by converting the VCM current into voltage and feeding back.
