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FUNCTIONAL EXPLANATION
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FUNTIONAL EXPLANATION
1. APC (Auto laser power control)
5. Tracking servo
This is the circuit to control laser power of pickup, and
laser ON/OFF is set by command from micro computer.
. RF Amplifier (| pattern output)
This inputs pickup photo diode output current (A+C) to
FIN2 (ipin), and (B+D) to FIN1 (2pin). Input current is
IV-converted, and output to RFSM
(41pin) of RFSM
amplifier output by. way of AGC circuit. Self-contained
AGC circuit has variable range of +3dB, and the time
constant can be varied by outside-fixed condenser of
PH1
(60pin). This also controls bottom level of EFM
signal (RFSM output), and this response can be varied
by outside-fixed condenser of BH1
(61pin). Central
gain of AGC variable range is set by resistance value
between RFSM (41pin) and RFS-(42pin).
. SLC (Slice level control)
SLC makes duty of EFM signa! which is input to DSP
50%. This judges duty, and decides DC level by inte-
grating EFMO signal which is output from DSP.
. Focus servo
Focus error signal can be gained by detecting the dif-
ference between
(A+C) and (B+D), which is (B+D)-
(A+C), and it is sent to FE (20pin). Focus error signal
gain is set by resistance value between FE (20pin) and
FE-(21pin).
FA amplifier is. phase compensating Amplifier, and the
equalizer curve is set by outside-fixed condenser and
resistance. Besides, this amplifier has muting function.
FD amplifier has the following functions; phase com-
pensating circuit, focus search signal synthesis, and
offset cancelling. Focus search starts by F-SERCH
command,
and generates lamp waveshape by inner
clock. Focus error signal by this waveshape detects in-
focus condition (focus zero cross), and turns on focus
servo. Lamp waveshape amplitude is set by resistance
between FD (16pin) and FD-(17pin).
This inputs pickup photo diode output current to E
(Spin) and F (4pin). input current is |V-converted, and
output to TE (7pin) by way of VCA circuit for balance
adjustment and VCA circuit for follow-up to RFAGC cir-
cuit. Tracking error gain is set by resistance between
TE-(6pin) and TE (7pin).
;
TOFF amplifier just after TE (7pin) turns off servo b
TOFF signal from DSP. |
TH amplifier varies servo response characteristic by
TGL signal from DSP. or by THLD signal of inside for-
mation by detecting JP signal. When DEFECT is de-
tected, inside mode changes into THLD. This can be
avoided by causing short circuit in DEF (49pin) to
"L"'=GND. In case of detection, gain can be automati-
cally up by configulating outside DC! (9pin) band pass
filter which picks up only shock element out of tracking
error signals and putting it in.
TO amplifier has the function of synthesizing JP pulse
and cancelling tracking offset: JP pulse is set by JP
(14pin) (THLD is detected inside ).
|
. Sled servo
SLEQ
(28pin) sets response characteristic. Amplifier
after SLEQ
(28pin) has muting function, and mutes
SLOF (38pin) by "H" or SLED OFF command. Sled
feed is operated by means of current input to SL-
(30pin) and SL+(31pin), that is, by connecting to output
port of micro computer by resistance and setting feed-
ing gain by the resistance value.
. Spindle servo
This configurates, together with DSP, servo circuit to
keep disc linear velocity at a scheduled level. This re-
ceives signal from DSP by CV-(39pin) and CV+(40pin),
and sets equalizer characteristic by SP (23pin), SP-
(36pin) and SPD (27pin) which output to SPD (27pin).
SPG (25pin) is set by resistance with which amplifier
gain of 12cm mode is connected to standard voitage.
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