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The signals from the sensors (I/J) are pre-amplified by the
gain amplifier, and then pass through the AGC/equalizer of
the SSI (IC831), and are then input to the RF signal terminal
of the ASIC (IC402). The AGC control signal (AGCOFFH) from
the ASIC (IC402) is modulated to control the on/off status of
the AGC. When the AGC is on, the wave pattern monitored at
TP801 is adjusted to a constant amplitude.
2-3-4. SERVO DRIVER
The driver circuit of spindle motor, sread motor and each ac-
tuators are accumulated inside BD6603KVT (IC815). The
spindle motor is used three aspect sensorless motor (DC
motor).
2-3-5. LASER POWER CONTROL
TA6015F (optical disc power control (LPC): IC841) and
TA6012F (optical disc high speed APC) are used in the pairs.
An APC IC appears on the pickup. LPC (IC841) control makes
it possible to set characteristics such as playback power, re-
cording peak power, duty, laser on/off setting and low power
consumption standby mode using the register settings of the
LPC (IC841).
3. BLOCK DIAGRAM OF PLAY/REC AND SIG-
NAL PROCESS etc.
1. Playback clock by PLL
The playback clock (20 MHz) which is generated from the
FCLKPP/FCLKNP signals (see Fig. 7) obtained from the FCM
is played back. The spindle motor operation is controlled by
CLV (constant linear velocity) to provide a constant FCM cycle
(26.6 µs). Accodingly, the rotation becomes faster as tracking
moves toward the center of the disc.
Magnetic field strength
MH
Driver
DRIVE ASIC
EQ, fc, Boost
MO
SSI
IC
2T signal
APC
Gain
IC
FCM
G.C
Slice Level
Gain
Adrs
ADRS
G.C
WCLK
LPC
IC
Duty Pr Pw
Temparature
sensor
APC IC (on the pickup)
The APC IC functions to maintain the current detected by the
photosensor attached to the laser to a constant level. This
has the effect of canceling any fluctuations in characteristics
resulting from the semiconductor laser temparature, and any
variances in production lots, so that the laser power can be
maintained at a stable level. The ON/OFF laser high-frequency
currents, power save and laser are output open corrector from
LPC IC, and input to APC IC.
Superimposing high-frequency currents
When a high-output semiconductor laser is used, interference
can be generated from the light which is reflected back from
the disc. Because of this, high-frequency currents of 300-600
MHz are superimposed on the laser drive currnet to reduce
interference.
2-3-6. SDRAM
This is used as a WORK for ECC encoding and decoding, as
a buffer for seamless recording and playback, and as a drive
cache.
Expectation
Tap coefficient
value
Digital
PRML
A/D
PR(1, 1)
EQI
RCLK
Delay
PLL
Dec.
Delay
Off Track
SH
quantity
Tilt Mark
CPU
– 8 –
ECC
2T/8T
amplitude
ratio
Fig. 10
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