cxa1992br Sony Electronics, cxa1992br Datasheet - Page 21

• Manufacturer Part Number: cxa1992br
• Description: Rf Signal Processing Servo Amplifier
• Manufacturer: Sony Electronics

• APC
When the laser diode is driven by a constant current, the optical power output has extremely large negative
temperature characteristics.
The APC circuit is used to maintain the optical power output at a constant level.
The laser diode current is controlled according to the monitor photo diode output.
• Laser power control
The RF level is stabilized by attaching an offset to the APC V
RF level fluctuations.
The RF_O and RF_I levels are compared and the larger of the two is smoothed by the RFTC's external CR.
This signal is then compared with the reference level.
The laser power is controlled by attaching an offset to V
reference level.
Set the reference level to 670mV. (center voltage reference)
LPC ON/OFF and LD ON/OFF control is performed with commands.
The laser power control limit can also be switched between ±50% and ±17% with commands.
APC & Laser Power Control
LPC
OFF
ON
ON
LPCL
±50%
±17%
—
C1
1µ
GND
10µH
L1
R1
Approximately 1.27V
Approximately 1.27V ± 625mV
Approximately 1.27V ± 208mV
22
V
LD PD
CC
0.01µ
C3
V
500
R2
L
100µ
130mV
C2
V
RF_O
variable range
RF_I
EE
PD
100
LD
R3
36
37
32
33
3V: 1.2V
5V: 1.52V
1.1Vpp
RF
V
EE
10k
R4
13k
R7
55k
– 21 –
R5
R6
1k
41k
R9
10k
R8
V
EE
R11
10k
L
V
CC
according to the results of comparison with the
L
R10
56k
and controlling the laser power in sync with the
R13
1M
V
L
V
R12
56k
EE
12.5k
R14
V
35
EE
LDON
C4
1µ
50%/17%
670mV
VREF
LPC ON/OFF
VC
V
EE
CXA1992BR