2. Working principle:
After powering on or closing to proper position (on loader frame for general DVD player, on PCB
board of below part of card door for PDVD player), loader lens begins to reset; after laser head is on
proper position, detect switch will give a signal to MT1389, MT1389 begins to output focus, main axis
and light emission signals, disc begins to rotate, laser head begins to recognise disc information, and
judges whether disc is CD or DVD according to disc information to facilitate to output level from IOA pin
to control disc switch circuit and laser head PDIC to make the corresponding control acts. At the same
time, Mt1389 adjusts laser output power through laser power control circuit.
After loader reading disc information, through photoelectric conversion, A, B, C, D, E, F signals are
formed to give to MT1389 (DVD only has A, B, C, D signals), and then inputted from pin 2~11, 18, 19 of
MT1389. After being amplified and processed by the pre-amplifier inside MT1389, now signals are
separated to two part s for processing inside MT1389. After being added amplifying and through
subtraction circuit, one part of signals produce servo error signals and form the corresponding servo
control signal after being processed by digital servo signal circuit and output FOO, TRO, DMO, FMO
servo control signals from pin 42, pin 41, pin 37, pin 38 of MT1389 respectively, through the integration
circuit composed by resistor and capacitor, FOSO, TRSO, DMSO, FMSO signals are sent to servo drive
circuit for amplifying and then brings along fucus coil, trace col, main axis electric machine and feed
electric machine after drive amplifying. Among these, focus and trace servo are used to correct objective
position accurately; feed servo is used to bring along laser head to make radial large-scale move which
belongs to the preliminary adjustment to pick-up position; and main axis servo is used to control main
axis electric machine to make it read signals in means of constant linear velocity and bring along disc to
rotate. After processing of amplification by VGA voltage control amplifier and equalization frequency
compensation inside MT1389, another part of signals are changed into digital signals through internal
A/D converter. When loader is reading CD/VCD signals, these signals are conducted EFM demodulation
inside MT1389, and then outputted to latter stage for AV decoding after finishing CIRC (Cross-
Interleaved Reed-Solomon Code) error correction inside. When loader is reading DVD signals, these
signals are conducted ESM demodulation inside MT1389, and then sent to latter stage for decoding
after finishing RSPC error correction inside. General DVD player has a open/close circuit, which controls
the in/out action of door to reach the purpose of conveying discs. PDVD player adopts manual means to
open the door, and you may judge whether door closes to proper position through detect switch.
3. Explanation to servo terms
(1) FOO: because of the error in disc make, when rotating, disc may probably move upwards or
downwards slightly to make the focus of laser emitted by pick-up cannot justly fall on data pit of disc, so
pick-up is required to move upwards or downwards to make focus aim at data pit justly. The main act is
to make object lens move upwards and downwards.
(2) TRO: data information is saved in disc in form of tracks. When disc is rotating, there will be track
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