CXA2647N
• EQ
The EQ internal block diagram is shown below. The EQ is configured with the filter of the Bessel function of
order 4.
Boost
Control
79.517fc2
S2 + (17.085fc) S + 79.517fc2
LPF1 =
24
BST
Amp
In
HPF1
LPF1
S2
Control Bias
VC – 1V to VC + 1V
HPF1 =
LPF2 =
S2 + (17.085fc) S + 79.517fc2
99.963fc2
S2 + (12.412fc) S + 99.963fc2
LPF2
Out
The boost gain can be adjusted by adjusting the HPF1
gain.
fc Control
The cut-off frequency is adjusted by the RFC external
resistance value and the VFC control voltage value.
RFC 26
33kΩ to 100kΩ
25 VFC
Control Bias
VC – 1V to VC + 1V
RFC resistance value: The cut-off frequency fc of each
filter is adjusted by the Pin 26
external resistance value.
The VFC voltage can be varied
using this fc as the reference.
The boost gain can be adjusted by the BST (Pin 24)
control voltage.
The control characteristics are shown in the graph
below.
The boost gain stands for the increased gain from the
low frequency gain in the fc frequency.
VFC voltage: fc can be adjusted by the voltage applied
to Pin 25. The cut-off frequency control
characteristics are shown in the graph
below.
Gain
1.5fc
8dB
fc
Freq.
5dB
Boost
gain
fc
0.5fc
–1dB
VC – 1.0
VC
VC + 1.0
VC – 1.0
VC
VC + 1.0
VFC voltage [V]
BST voltage [V]
RFC pin external resistor value 100kΩ: fc = 1.6MHz
33kΩ: fc = 4.8MHz
• APC (Automatic Power Control)
When the laser diode is driven by a constant current, the optical power output has extremely large negative
temperature characteristics. Therefore, the current must be controlled to maintain the monitor photodiode
output at a constant level. This control is performed by the APC function.
VCC
56k
PD
2
1
LD
10k
1k
55k
56k
10k
10k
1.25V
– 10 –
SONY [ SONY CORPORATION ]
