Fujitsu MHV2040AH - Mobile - Hard Drive, Product Manual

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4.3 Circuit Configuration
C141-E217 4-3
4.2.4 Air filter
There are two types of air filters: a breather filter and a circulation filter.
The breather filter makes an air in and out of the DE to prevent unnecessary
pressure around the spindle when the disk starts or stops rotating. When disk
drives are transported under conditions where the air pressure changes a lot,
filtered air is circulated in the DE.
The circulation filter cleans out dust and dirt from inside the DE. The disk drive
cycles air continuously through the circulation filter through an enclosed loop air
cycle system operated by a blower on the rotating disk.
4.3 Circuit Configuration
Figure 4.1 shows the power supply configuration of the disk drive, and Figure 4.2
shows the disk drive circuit configuration.
(1) Read/write circuit
The read/write circuit consists of two circuits; 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 Modified Extended Partial
Response (MEEPR), and contains the Viterbi detector, programmable filter,
adaptable transversal filter, times base generator, data separator circuits,
RLL (Run Length Limited) encoder and servo demodulation circuit.
(2) Servo circuit
The position and speed of the voice coil motor are controlled by closed-loop servo
using the servo information recorded on the data surface. The servo information is
an analog signal converted to digital for processing 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 and controls the motor speed comparing target
speed.