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3-2.
Servo Operation at DVD Play
3-2-1.
Optical Pickup Control
(1) DVD focus servo
The focus error signal output from the optical pickup for DVD (hereinafter referred to
as optical pickup) is entered to the TK-47 board IC006: SSI33P3720A A to D (!º to
7P).
7P).
The balance amount and offset amount of the focus error signal is set by IC805 (CPU)
via IC804 of the MB-78 board using the internal register of IC006.
The focus error signal is generated at TK-47 board IC006, amplified, and output from
the FE terminal (#ªp).
The IC006 FOCUS error (DVD FE) signal is input to the MB-78 board via the flexible
flat cable.
The error signal is switched according to whether the disc type is DVD or CD by the
switch IC452, its signal level is adjusted by IC503 (OP amplifier 8, 9, !ºp), and it is
input to the servo DSP IC506 (CXD8730R) @§p.
– 34 –
– 35 –
Figure 3-1.
DVD focus servo, drive
14
Optical Block
13
6
18
14
13
6
18
A
B
C
D
21
17
18
19
23
22
DVD FE
7
11
10
From IC804
CXD8728 LGA
To DVD FOCUS coil
9
5
6
10
39
37
44
3
4
10
8
26
46
26
15
16
21
7
7
1
3
3
9
11
19
5
13
12
43
45
16
9
8
7
ZIF
CN001
CN005
CN452
IC452
MC14053
IC503 (1/4,3/4)
NJM3403
BUFF
IC506
CXD8730R
IC363
BA5981
DVD FCS–
FCS DRIVE
SERVO DSP
FE
PI
IC501 (1/2)
µ
PC393
DEFECT
DET
DFCTA
FOUT
DVD FCS+
MB-78 board
DVD : H
CD : L
AGC
IC006 SSI33P3720A
TK-47 board
L
P
F
S
U
M
A
M
P
DVD PI
SSSD
SCKG3
SDEN
DVDLDON
– 36 –
The IC506 Servo DSP: CXD8730 on MB-78 board provides the following control in
the focus servo system.
(a) Focus search
The optical pickup lens is moved toward a disc to turn on the focus servo.
The focus servo loop is turned on when the PI (Pull IN) signal (used for FOK:
Focus OK) exceeds the specification (Vc +0.25V) and the FE signal zero-crossing
is detected.
(b) Focus gain adjustment
The gain of digital filter in the IC506 is automatically adjusted so that the focus
servo loop gain becomes optimum.
Consequently, the optimum gain for each disc to be played can be attained, besides
correction of gain variations in focus actuator (coil) and optical pickup sensor
(photodiode for focusing).
(c) Focus bias adjustment
The focus bias is added to the focus servo filter so as to minimize the jitter.
Consequently, a variation of optical pickup and disc can be automatically corrected.
(d) Focus jump
Operation carried out when playing back the DVD dual layer disc to perform
focusing jump between layer 0 (PU side layer) and layer 1 (far end layer).
First the servo loop is turned off, the kick voltage is supplied to the focus actuator,
and the focus is jumped to the targeted layer. As the focus approaches the desired
layer, the FE signal appears. The voltage of this signal is monitored, the deceleration
pulse is generated, and the focus servo is turned ON again after focusing.
These operations from the start to end of jumping are all performed inside the
DSP.
– 37 –
Figure 3-2. Example of S-shape
waveform for the DVD disc
(single layer) MB-78 board
CN303
3
P
Figure 3-3. Example of S-shape
waveform for the DVD disc
(dual layer) MB-78 board
CN303
3
P
Figure 3-5. Example of S-shape
waveform for MB-78 board
CXD8730R (Layer) MB-78
board CN303
3
P
Figure 3-4. Focus jump waveform
FOK
PI
FE
FOUT
BUSY
88
89
21
99
4
100
49
46
41
38
75
74
73
24
26
MIRR
TZC
PI
TE
FE
SOUT
D/A
DSP CORE
PWM
RAM
SDCNT
HYCNT
SLOFS
TIOFS
TOUT
FOUT
FON
DFCTS
BUSY
PROGRAM
ROM
A/D
SWITCH
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