Theory of Device Operation
4.3 Circuit Configuration
Figure 4.2 shows the disk drive circuit configuration.
(1) Read/write circuit
The read/write circuit consists of two LSIs; read/write preamplifier (PreAMP) and read channel (RDC).
The PreAMP consists of the write current switch circuit, that flows the write current to the head coil, and the voltage amplifier circuit, that amplitudes the read output from the head.
The RDC is the read demodulation circuit using the partial response class 4 (PR4), and contains the Viterbi detector, programmable filter, adaptable transversal filter, times base generator, and data separator circuits. The RDC also contains the 8/9 group coded recording (GCR) encoder and decoder and servo demodulation circuit.
(2) Servo circuit
The position and speed of the voice coil motor are controlled by 2 closed-loop servo using the servo information recorded on the data surface. The servo information is an analog signal converted to digital for processeing by a MPU and then reconverted to an analog signal for control of the voice coil motor.
The MPU precisely sets each head on the track according on the servo information on the media surface.
(3) Spindle motor driver circuit
The circuit measures the interval of a PHASE signal generated by counter- electromotive voltage of a motor at the MPU and controls the motor speed comparing target speed.
(4) Controller circuit
Major functions are listed below.
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Data buffer (128 KB) management
ATA interface control and data transfer control
Sector format control
Defect management
ECC control
Error recovery and self-diagnosis
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