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2. Focus Circuit
2-1. Block Diagram
Disc
Optical
Motor unit
Pick-up
HOP-8541T
FACT-
FACT+
FACT-
2-2. Focus Servo
The aim of Focus Servo is to maintain the distance between object lens of P/U and disc surface, so that the
detected RF signal(A1, A2, A3, A4, B1, B2, B3, B4, EF1, EF2, EF3, EF4) can be maximized.
Focus Error Signal(FE) generates from focus error detection block in RF IC(HD153722) using Double knite
Edge method (DVD), spot size Detection method(CD).
Focus Gain and path can be changed at the RF IC(HD153722) according to the disc, and the resulting output
FE(HD153722 4pin) is input to DSP IC(HD153722 100pin).
The Focus Search operation is using FE, PE Signal, therefore check FE, PE signals when Focusing is failed.
The role of DSP IC(R8J32005FP) is Focus Digital Controller. The operation path is as follows;
FE Signal is input to DSP IC(R8J32005FP 100pin), and after A/D Conversion, Digital Equalizer Block and D/A
Conversion in R8J32005FP, the output signal FOD(R8J32005FP 116pin) is input to Drive IC(M63041AFP
40pin).
The drive output signal FACT+/FACT- generated according FOIN(M63041AFP 40pin), and drives focus actuator
in the P/U unit.
DVD : A1+A2+A3+A4
CD : EF1+EF2+EF3+EF4
(EF1~EF4)
A1~A4
B1~B4
(EF1~EF4)
DVD : (B1+B3)-(B2+B4)
CD : (EF1+EF3)-(EF2+EF4)
FOD
FACT+
34
IC601
35
M63041AFP
LPF
IC101
HD153722TF
LPF
Focusing
116
DAC
Compensator
IC301
R8J32005FP
FOIN
40
REF
42
EN1
20
CTL1
EN2
21
CTL2
HAVC
LS
G
5
to
0.8V
HAVC
LS
4
G
to
V14
ADC
C608
PE
FE
FE
R334
C325
FE
GND
100
101
PE
R615
FOD
1.65V
43
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