CXA1992BR
Notes on Operation
1. Focus OK circuit
1) Refer to the "Description of Operation" for the time constant setting of the focus OK amplifier LPF and the
mirror amplifier HPF.
2) The equivalent circuit for the output pin (FOK) is shown in the diagram below.
VCC
20k
FOK
27
40k
RL
The FOK and comparator output are as follows:
100k
Output voltage High : VFOKH ≈ near Vcc
VCC
Output voltage Low : VFOKL ≈ Vsat (NPN) + VEE
VEE
VEE
2. Sled amplifier
The sled amplifier may oscillate when used by the buffer amplifier. Use with a gain of approximately 20dB.
3. Focus/Tracking internal phase compensation and reference design material
Item
1.2kHz gain
1.2kHz phase
1.2kHz gain
1.2kHz phase
2.7kHz gain
2.7kHz phase
SD
Measurement pin
6
Conditions
Typ.
21.5
63
Unit
dB
08
08
25
25
CFLB = 0.1µF
CFGD = 0.1µF
deg
dB
13
–125
26.5
–130
deg
dB
13
CTGU = 0.1µF
25 → 13
25 → 13
deg
4. Laser power control
The RF level is stabilized by attaching an offset to the APC VL and controlling the laser power in sync with the
RF level fluctuations.
The laser life is shortened by increasing the laser power when the less light is reflected from the disc.
It is recommended that the typical laser power value is set lower to maintain the laser life.
Take care of the laser maximum ratings when using the laser power control circuit.
5. RF amplifier
The phase compensation value in the IC is set on condition that 20 to 30p capacitance of optical pickup and
line material is attached.
In case of voltage output-type pickup, resistor is inserted in series prior to PD1/PD2 pins. It looks capacitance
that attach to PD1/PD2 pins becomes smaller.
At this time, RF amplifier may oscillate. Connect a capacitance around 5 to 20p between PD1/PD2 pins and
GND, and use it.
– 48 –
SONY [ SONY CORPORATION ]
