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5
1.2.3 Carriage servo system
In the carriage servo system, the low frequency component from the tracking equalizer (the information on the lens
position) is transferred to the carriage equalizer, where the gain is increased to a certain level, and then sent out from
the LSI as the carriage drive signal. This signal is applied to the carriage motor via the driver IC.
During the play mode, when the lens offset reaches a certain level, it is necessary to move the pickup toward the FOR-
WARD direction. The equalizer gain is adjusted so that the output over the carriage motor starting voltage is sent out
in such a case. In actual operations, only when the equalizer output exceeds the threshold level preset in the servo
LSI, the drive signal is sent out. This can reduce the consumption power.
With an eccentric disc loaded, before the whole pickup starts moving, the equalizer output may exceed the threshold
level a few times. In this case, the drive signal applied from the LSI shows pulse-like waveforms.
UPD63760GJ
From
TRACK EQ.
KICK, BRAKE
REGISTERS
Fig. 1.2.7 Block diagram for the carriage servo block
TRACKING DRIVE
(LOW FREQUENCY)
LENS POSITION
CRG DRIVE
(INSIDE UPD63711GC)
CRG MOTOR VOLTAGE
Fig. 1.2.8 Waveforms of the carriage signal
5
6
DIG.
EQ
CONTROL
DRIVE ON/OFF THRESHOLD
CARRIAGE MOVED AT THESE POINTS
6
7
BA5996FM
107
SD
PWM
24
CX-3057
7
8
18 LCOP
M
LCOM
17
CARRIAGE
MOTOR
8
A
B
C
D
E
F
11
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