cxa1992ar Sony Electronics, cxa1992ar Datasheet - Page 26

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cxa1992ar

Manufacturer Part Number
cxa1992ar
Description
Rf Signal Processing Servo Amplifier
Manufacturer
Sony Electronics
Datasheet

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Part Number:
CXA1992AR
Manufacturer:
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CXA1992AR
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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 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
33
a
a
b
e
c
RF_O
RF_I
DEFECT AMP
RFO
DEFECT
AMP
BOTTOM
HOLD (1)
solid line
CC1
DFCT1
2
33
32
b
RF
FOCUS OK AMP
CB
30
RFI
15k
0.01µ
– V
DEFECT BOTTOM
HOLD
1
RFO
VG
– 26 –
–0.37V.
CC1
54k
29
0.63V
0.033µ
92k
DEFECT COMPARATOR
28
CC2
FOCUS OK
COMPARATOR
c
d
DFCT1
DEFECT SW
FLIP
FLOP
e
H
L
d
SENS
SELECTOR
DFCT2
20k
BOTTOM
HOLD (2)
dotted line
CC2
V
CC
27
26
25
FOK
SENS2
SENS1
CXA1992AR

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