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3-2. Focus Servo for CD/DVD
Focus Servo for CD/DVD is based on focus error signal generated from RF AMP (SSI3723). It standardizes the
laser beam (CD : A, B,C, DVD : A, B,C,D) radiated from the pick-up.
Each other focus gain or path is made at the SSI3723 (IC301) according to the disc, Focus Error signal
output from the FE terminal and input to Servo IC (IC701 CXD3030R).
After the first amplification of this signal, the signal is converted to A/D and input to Digital Equalizer Block
assigned the most important part at the Focus Servo, and generates the focus servo with coefficient value
set at the µ-COM through the Digital Filter.
At this Digital Equalizer, auto adjustment for Focus Balance or Focus Loop Gain occurs and the basic offset
value for pick-up is accepted on the balance mode, and set the focus standard level to this value.
After the signal for Focus Servo is converted to the D/A and output through FAO (IC701 CXD3030R
This signal drives Focus Actuator through the Focus Drive IC (IC501:BA5983FM).
3-3. Tracking Servo for CD/DVD
For Tracking Servo, CD uses 3 Beam method (E-F), DVD uses DPD (Differential Phase Detect) method
[Phase (A+C) - Phase (B+D)]
According to the disc, Tracking Error is set at SSI3723, Gain or Path differs from each other, and the
generated signal output through the TE terminal.
This signal input to TE of IC701, after the first amplification, and converted to A/D.
The signal converted to A/D input to the Digital Equalizer assigned the most important part at the Tracking
Servo, Tracking Servo Gain is generated with Digital Filter coefficient value set according to the disc at the
µ-COM.
* Tracking signal is converted to D/A through the pin
(BA5983) tracking drive.
This drive drives the tracking actuator actually.
3-4. Sled Servo (Feed Servo) for CD/DVD
Sled servo operates related with a tracking servo basically
It goes with the progressive track speed according to the disc rotation speed.
Sled drive voltage is generated with a accumulated capacity of tracking error signal and is applied sled
movement voltage according to the track movement capacity, and this voltage outputs to the pin
IC701. This value is the sled motor drove by the IC501 (Sled drive : BA5983FM). But, the shift speed
for pick-up is not controlled and broke with a only sled servo, itself, in the data access mode, and the
feedback is used according to the sled shift speed at this time. So, the accurated shift speed for
pick-up is controlled added to the sled signal.
The hall sensor is used in the feedback and SLEDCLK (95) output at the µ-COM (IC203) is used with it
in the sled kick or break.
16
3
TAO terminal of IC701 and input to IC501
4
).
113
FAO of
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