CXA1782 SONY [Sony Corporation], CXA1782 Datasheet - Page 20

• Manufacturer Part Number: CXA1782
• Description: RF Signal Processing Servo Amplifier for CD players
• Manufacturer: SONY [Sony Corporation]

Focus OK Circuit
The focus OK circuit creates the timing window okaying the focus servo from the focus search state.
The HPF output is obtained at Pin 30 from Pin 31 (RF signal), and the LPF output (opposite phase) of the
focus OK amplifier output is also obtained.
The focus OK output reverses when V
Note that, C5 determines the time constant of the HPF for the EFM comparator and mirror circuit and the LPF
of the focus OK amplifier. Ordinarily, with a C5 equal to 0.01µF selected, the fc is equal to 1kHz, and block
error rate degradation brought about by RF envelope defects caused by scratched discs can be prevented.
DEFECT Circuit
After the RFI signal is reverted, two time constants, long and short, are held at bottom. The short time constant
bottom hold responds to 0.1ms or greater disc mirror defects, and the long time constant bottom hold holds the
pre-defect mirror level. By differentiating and level-shifting these constants with capacitor coupling and
comparing both signals, the mirror defect detection signal is generated.
RF_O
0.01µ
C5
31
RF_O
RF_I
a
b
e
c
a
BOTTOM
HOLD (1) ;
solid Line:
CC1
RFO
DEFECT
AMP
DEFECT
DEFECT AMP
30
31
2
b
RF
FOCUS OK AMP
RFI
CB
15k
– V
28
0.01µ
RFO
1
VG
DEFECT BOTTOM
HOLD
–0.37V.
– 20 –
54k
0.625V
CC1
27
92k
0.033µ
DEFECT COMPARATOR
FOCUS OK
COMPARATOR
26
CC2
d
c
DEFECT SW
e
L
H
d
20k
BOTTOM
HOLD (2) ;
dotted Line:
CC2
V
CC
24
25
SENS
FOK
CXA1782CQ/CR