30
YPM-2306ZF
2) RF Amplifier and RFAGC Amplifier
The photo-detector outputs (A
+
C) and (B
+
D) are
added, amplified and equalized on this LSI and then
output to the RFI terminal as the RF signal. (The eye
pattern can be checked by this signal.)
The RFI voltage low frequency component is :
RFI = (A
+
B
+
C
+
D)
×
3.2
RFI is used on the FOK generator circuit and RF offset
adjusting circuit.
R207 is an offset resistor for maintaining the bottom
reference voltage of the RFI signal at 1.5 VDC. The D/A
output used for the RF offset adjustment (to be
described later) is entered via this resistor.
After the RFI signal from Pin 77 is externally AC cou-
pled, entered to Pin 76 again, then amplified on the
RFAGC amplifier to obtain the RFO signal.
The RFAGC adjustment function (to be described later)
built-in the LSI is used for switching feedback gain of
the RFAGC amplifier so that the RFO output may go to
1.5
±
0.3Vpp.
The RFO signal is used for the EFM, DFCT, MIRR and
RFAGC adjustment circuits.
3) RFOK Circuit
This circuit generates the signal that is used for indicat-
ing the timing of closing the focus or state of the focus
close currently being played. This signal is output from
Pin 2 as the FOK signal. It goes high when the focus
close and in-play.
The RFOK signal is generated by holding DC level of the
RFI at its peak with the succeeding digital section, then
comparing it at a specific threshold level. Thus, the
RFOK signal goes high even if the pit is absent. It indi-
cates that the focus close can take place on the disc mir-
ror surface, too.
This signal is also supplied to the micro computer via
the low pass filter as the FOK signal and used for the
protection and the RF amplifier gain switching.
CN101
84
6
13
83
82
10k
10k
85
FOK
CIRCUIT
A/D
4
A+C
16k
B+D
10k
16k
10k
R207
12k
C216 3pF
R205
10k
R206
1.8k
C217
27pF
R204
10k
80
79
74
75
76
77
D/A
12k
66
10k
RFO
AGCI
RFI
C215
0.1
µ
F
C213
3900pF
FOK
TO EFM
CIRCUIT
Fig.3 : RFAMP, RFAGC AND FOK CIRCUIT
Содержание YPM-2106ZF
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Страница 11: ...11 YPM 2306ZF ...
Страница 13: ...13 YPM 2306ZF 1 2 3 4 1 2 3 4 D C B A SIDE B A CLAMP CONTROL UNIT S8 A ...
Страница 19: ...19 YPM 2306ZF Grating waveform Ech Xch 20mV div AC Fch Ych 20mV div AC 45 0 75 60 30 90 ...