CX-954
1.CIRCUIT DESCRIPTIONS
1.1 Front-end processor (FEP) section (AN8702FH: IC1100)
The IC1100 generates servo signals for focus and tracking operations and increments the RF signal and also controls
the laser power of the pick-up.
The IC contains a focus calculation amplifier, a focus balance adjustment circuit, a three-beam tracking calculation
amplifier, a phase difference tracking detection circuit, a tracking balance adjustment circuit and an envelope detection
circuit for servo controls.
For the RF signal processing the AGC and equalizer functions are contained in the IC as well.
1.1.1 APC circuit
1.1.2 FE generation circuit
1.1.3 TE generation circuit
+5V
3.9& 3.9& 3.9& 3.9&CN1100
For CD
170mVCDLD1
+
-
+428
LPC0278LD
CDLD0
3
10
78MD
LPC2
+5V+5V
3.9& 3.9& 3.9& 3.9&
MD
+
For DVD
180mV+DVDLD1
CDDVD
-
LDLD
+230
LPC0165LD
DVDLD0
1
12
65MD
LPC1
AN8702FHPU UNIT
1.1.1 APC circuit
The light output of the laser diode (LD) has a large negatively charged thermal characteristic. The APC circuit is
designed to stabilize the light output at the monitor diode (MD), by controlling the current. AN8702FH contains two
types of APC circuits, one for DVDs and the other for CDs. The LD current can be obtained by dividing the voltage
reading between positions DVDLD1 (CDLD1) and 5V by 15.6 & (3.9 & x 4 = 15.6 & ). For DVDs (CDs), it is approximately
26 mA (44mA).
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ACEC
