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PDF CXB1818Q Data sheet ( Hoja de datos )
| Número de pieza | CXB1818Q | |
| Descripción | Laser Diode Driver | |
| Fabricantes | Sony Corporation | |
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Laser Diode Driver
CXB1818Q
Description
The CXB1818Q is a high-speed monolithic Laser
Diode Driver/Current Switch with ECL/PECL input
level. Open collector outputs are provided at the
output pins (Q, QBX) and have the capacity of driving
modulation current of 50mAp-p at a maximum data
rate of 622Mbps. Along with the modulation current
generator there is the laser diode bias current
generator which has capacity of sourcing up to 60mA
(Bias). The laser diode bias current can be controlled
by either a voltage or current into the bias adjust pin
(BiasAdj) and the bias set pin (SBias), depending on
how these pins are configured. Control of the bias
current is achieved through the APC (Automatic
Power Control) circuit. In order to avoid having a
large current go through the laser diode, this IC also
provides an Activity detector function for laser
protection. The Activity detector circuit detects data
edge transitions and if no data transition occurs after
a certain period, then both the modulation and bias
currents are shutdown. The bias currents are shut it
down by in order to pull down the output voltage of
APC OP.Amp.
When the automatic shutdown is conducted, it is
possible to select whether the laser diode alarm
output is activated or not. Additionally, this IC has
the DFF for the input signal correction and the
internal Duty Cycle correction circuit that can control
the falling edge of the input pulse up to a maximum
of 1.0ns(Min.).
40 pin QFP (Plastic)
Applications
• SONET/SDH: 622Mbps
• Fibre channel: 531Mbps
Absolute Maximum Ratings
• Supply voltage VCC – VEE –0.3 to +6.0
• Input voltage VIN
VEE to VCC
• Differential input voltage
| VD – VDB |
0 to 2.5
• Bias output current
0 to 80
• SBias input/output current
0 to 5
• Bias control current
IBset (Ibiasadj) 0 to 5
• Bbias control voltage
VBset (Vbiasadj) 0 to 3
• Modulation output current
70
• Modulation adjust current
IQset (Idrvadj) 0 to 15
• Storage temperature
Tstg –65 to +150
V
V
V
mA
mA
mA
V
mA
mA
°C
Features
• Maximum data rate (NRZ): 622Mbps
• Alarm and Shutdown function
• DFF for input signal correction
• Input signal Duty cycle correction
• Automatic Power Control (APC) for bias current
Recommended Operating Conditions
• DC supply voltage
VCC – VEE 3.14 to 3.46
• Operating ambient temperature
Ta –40 to +85
V
°C
• Activity detector function for laser protection
• Alarm signal mask function during shutdown
• Differential PECL inputs or AC coupled inputs
Structure
Bipolar silicon monolithic IC
Sony reserves the right to change products and specifications without prior notice. This information does not convey any license by
any implication or otherwise under any patents or other right. Application circuits shown, if any, are typical examples illustrating the
operation of the devices. Sony cannot assume responsibility for any problems arising out of the use of these circuits.
–1–
E99227-PS
1 page  
CXB1818Q
Pin
No.
Typical pin voltage [V]
Symbol
DC AC
20 ClkB
1.6 to 2.4
21 Clk
1.6 to 2.4
Equivalent circuit
VCC
550 550
20
200
21
200
400µA
VEE
Description
Differential PECL clock
input.
22 VEE2
23 DB
24 D
25 VCC2
0
1.6 to 2.4
1.6 to 2.4
3.3
VEE
26 MaskSel
or
open
27 RSB
0.5
28 RS
2.0
Negative power supply
25 for data input circuit.
300 300
24
23
200
200 10k
Differential PECL data
input.
10k
1mA
300µA
22 Positive power supply
for data input circuit.
VCC
1k
26
VEE 2.2k
9k 4.5k 4.5k
2.2k
Alarm signal control for
optical power output
forced shutdown.
High (open):
Alarm signal is
High for shutdown.
Low (connect to VEE):
Alarm signal stays
Low for shutdown.
VCC
28
27
VEE
100µA
2.5k
15k
5k
Window comparator
top/bottom threshold
voltage for LD_ALARM.
The alarm (fault) assert
voltage can be set by
the external resistor.
Default voltages are
RS equal to 2.0V and
RSB equal to 0.5V.
(Option)
–5–
5 Page 
CXB1818Q
The laser diode alarm output state can be controlled by the alarm signal control pin (Pin 26 MaskSel) for the
optical power output forced shutdown. When the automatic shutdown is conducted and MaskSel pin is left
open, the laser diode alarm output goes High. The laser diode alarm output is kept Low (disable) by connecting
MaskSel pin to VEE.
5. Shutdown and Input Alarm Circuits
These circuits disable both the modulation current and the bias current under various conditions. The function
block diagram for all of the shutdown mechanisms for the circuit is shown in Fig. 5.
The Shutdown circuit has complementary TTL input to disable the output current. Shown below is the desired
truth table for the shutdown function.
SDN
Low
Low
High
High
SDNB
Low
High
Low
High
Output current
Off
On
Off
Off
The Activity detector (In_ALM) circuit is designed to detect the input data edge transition. If there is no input
data transition over a certain period determined by the user (TACT), the Shutdown circuit is enabled, causing
the modulation current and bias current to be shutdown. The Inactive time (TACT) is set by the external
capacitor value between Timer (Pin 17) and VCC. The relation between the Inactive time and Ctimer is shown
in Fig.6.
SDN
SDNB
D
DB
Shutdown
In_ALM
Switch
To modulation and
bias current
Shutdown circuits
Timer ADCDis
Fig.5. Shutdown and In_ALM Functional Block Diagram
6. Others
Pay attention to handling this IC because its electrostatic discharge strength is weak.
The Tset pin (Pin 31) should be connected to VCC through a resistor.
Do not leave this pin open or connect to VCC directly.
– 11 –
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet CXB1818Q.PDF ] | |
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