cxa1992br Sony Electronics, cxa1992br Datasheet - Page 26

• Manufacturer Part Number: cxa1992br
• Description: Rf Signal Processing Servo Amplifier
• Manufacturer: Sony Electronics

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 32 from Pin 33 (RF signal), and the LPF output (opposite phase) of the focus
OK amplifier output is also obtained.
The focus OK output is inverted when V
Note that, C5 determines the time constant of the HPF for the 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 inversion, RF_O signal is bottom held by means of the long and short time constants.The long time
constant bottom hold keeps the mirror level prior to the defect.
The short time-constant bottom hold responds to a disc mirror defect in excess of 0.1msec, and this is
defferentiated and level-shifted through the AC coupling circuit.
The long and short time-constant signals are compared to generate at mirror defect detection signal.
RF_O
0.01µ
C5
33
RF
a
RF_O
RF_I
DEFECT AMP
FOK
2
33
32
b
a
b
e
c
f
BOTTOM
HOLD (1)
solid line
CC1
RFO
DEFECT
AMP
DFCT1
INT
RF
FOCUS OK AMP
CB
30
DEFECT
0.01µ
RFI
15k
– V
DEFECT BOTTOM
HOLD
1
RFO
VG
CC1
– 26 –
–0.37V.
29
54k
0.033µ
0.63V
DEFECT COMPARATOR
92k
INTERRUPTION
COMPARATOR
28
CC2
f
d
c
FOCUS OK
COMPARATOR
DFCT1
DEFECT SW
FLIP
FLOP
L
L
H
H
e
d
SENS
SELECTOR
BOTTOM
HOLD (2)
dotted line
CC2
DFCT2
20k
V
CC
26
25
27
SENS2
SENS1
FOK
CXA1992BR