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1. CIRCUIT DESCRIPTIONS
Recently, most CD LSI's have included DAC, RF amplifier and other peripheral circuits, as well as the core circuit DSP.
This series of mechanisms employ a multi-task LSI UPD63761GJ, which has CD-ROM decoder and MP3/WMA decoder
in addition to the CD block as shown in the Fig.1.0.1. This enables to reproduce a CD-ROM where MP3/WMA data is
recorded.
Fig.1.0.1 Block diagram of CD LSI UPD63761GJ
A-F
UPD63761GJ Audio outputDigital servoRF amplifierCD-ROM
decoder
EFM
Signal
processor
MicrocomputerSRAM(1Mbit)
Buffer memory
controller(BMC)
DAC MP3/WMA
decoder
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1.1 PREAMPLIFIER BLOCK (UPD63761GJ: IC201)
In the preamplifier block, the pickup output signals are processed to generate signals that are used for the next-stage
blocks: the servo block, demodulator, and control.
After I/V-converted by the preamplifier with built-in photo detectors (inside the pickup), the signals are applied to the
preamplifier block in the CD LSI UPD63761GJ (IC201). After added by the RF amplifier in this block, these signals are
used to produce necessary signals such as RF, FE, TE, and TE zero-cross signals.
The CD LSI employs a single power supply system of + 3.3V. Therefore, the REFO (1.65V) is used as the reference volt-
age both for this CD LSI and the pickup. The LSI produces the REFO signal by using the REFOUT via the buffer amplifi-
er and outputs from the pin 133. All the measurements should be made based on this REFO.
Caution: Be careful not to short the REFO and GRD when measuring.
1.1.1 APC (Automatic Power Control)
A laser diode has extremely negative temperature characteristics in optical output at constant-current drive. To keep
the output constant, the LD current is controlled by monitor diodes. This is called the APC circuit. The LD current is
calculated at about 30mA, which is the voltage between LD1 and V3R3D divided by 7.5 (ohms).
Fig. 1.1.1 APC
PICKUP UNIT CD CORE UNIT
MD
VR
LD-
LD+5
7
15
145
7
15
14
100P
R1 R1100/162SB1132
1SS355
1R5 x 5
++
-
+
-
+
- PD
VREF REG 1.25V
APN
LDS
UPD63761GJLD
143
142
6R5K
1K 6R5K
1K
110K100K
100K
3P
