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2-3. OUTLINE EXPLANATION FOR EACH BLOCK OF
DRIVE CIRCUIT BOARD (MC3)
2-3-1. SERVO AMPLIFIER
They are amplifier part for the focus servo and the tracking
servo.
Minute
amplitude
inside
C D
B A
Land
Land
Groove Groove
1. Focus offset adjustment
When the servo and laser are both off, the DSP of the ASIC
(IC402) samples the FE (focusing error) signal and obtains
average values which are used to control the offset cancel
registers of SSI33P3721 (IC402) in order to cancel the electri-
cal offset. The signal level is set to 2.5 V DC.
2. Focus gain adjustment
The DSP of the ASIC (IC402) carries out focus searching to
measure the peak levels (+/–) for the S-shaped characteris-
tics of the FE signal, and sets the ABCD gain (focus gain) for
the SSI (IC831) in accordance with these values. The above
2. TRACKING SERVO (MAIN PP AND PP SUBTRAC-
TION METHOD)
Servo control is carried out by the DSP which is built into the
ASIC (IC402). This controls the tracking actuator and the thread
inside
outside
A, B, C, D
H F
C D
B A
E G
E, F, G, H
Land
Land
Land
Groove Groove
Tracking
actuator
Sread
actuator
outside
IC831
SSI33P3721
FES Matrix
Gain-Amp
[Kf(A+C)-(B+D)]
(x1.4)
A, B, C, D
Land
Focus
actuator
Main Beam PP
[(A+D)-(B+C)]
Gain-Amp
(±6dB)
IC814
IC837
IC814
(AD8054)
(AD8051)
(AD8054)
Sub Beam PP
α[(F+G)-(H+E)]
Offset
adjustment
IC814
(AD8054)
1. FOCUS SERVO (DISC SURFACE RUNOUT TRACK-
ING CONTROL)
Servo control is carried out by the DSP which is built into the
ASIC (IC402). This controls the focus actuator of the pickup in
order to carry out surface runout tracking control.
2.5V
The S-shaped curve amplitude of the focus error signal
(FE signal) is TYP 1.2Vp-p
GND
Focus error singal
observation terminal
(TP810)
Gain-Amp
Read (x1.22)
AGC
Write (x0.76)
FES
OFFSET
CANCEL
IC835
(AD8532)
AGC on/off
WG
IC833
(ADG702)
"0" REC
"1" PLAY
BD6603KVT
2.5V
ABCD gain for the SSI is adjusted by the microprocessor in
order to maintain the VPP for the S-shaped characteristics of
the FE signal to approximately 1.18 V. The ABCD gain for the
SSI can be adjusted within the range of x1.2 to x4.3. During
recording (when the laser is at high power), the signal ampli-
tude is reduced by about half before the FE signal is input to
the DSP of the ASIC (IC402).
3. Focus servo ON
The DSP of the ASIC (IC402) moves the focus actuator up
and down to control the FE signal so that its AC component is
"0".
actuator of the pickup in order to carry out rotation offset track-
ing control.
Tracking error signal
observation terminal
SSI33P3721
2x[(A+D)-(B+C)]-
Gain-Amp
TZC
α[(F+G)-(H+E)]
(x1~x2.2)
OFFSET
LPF
CANCEL
WG
"0" REC
"1" PLAY
2.5V
– 5 –
DRIVE ASIC
DSP
MACRO
FES
PWM 3/4
FCSF FCSR
4
5
IN2F
IN2R
H2F
H2R
IC815
OUT
OUT
14
12
The OA amplifiers and power supply
of the analog switches are all 5V.
(TP811)
TZC
(tracking
Buf
TZC
zero cross)
TES
FES
IC835
PWM 5/6
(AD8532)
SLDFSLDR
TRKFTRKR
2
3
IC834
IN1F
IN1R
(ADG702)
H1F
H1R
IC815
OUT
OUT
BD6603KVT
9
7
Fig. 4
DSP
MACRO
PWM 1/2
36
35
IN4F
IN4R
H4F
H4R
OUT
OUT
40
42
Fig. 5
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