155Mbps to 2.5Gbps Burst-Mode
Laser Driver
Running Burst Enable
Single Ended
With PECL signal levels, for single-ended operation of
burst enable, connect the BEN+ to the burst-enable
control. Connect a resistor (R1) from VCC to BEN- and
resistor (R2) from BEN- to ground. The parallel combina-
tion of R1 and R2 should be less than 1kΩ. Choose the
values of R1 and R2 to set the common-mode voltage in
the range defined in the Electrical Characteristics table
(see Figure 6).
With LVTTL or LVCMOS signal levels, for single-ended
operation of burst enable connect a 4kΩ (R4) resistor
from the burst-enable signal to BEN+. Connect a 1kΩ
(R3) resistor from VCC to BEN+. Connect a 1kΩ resistor
(R5) from VCC to BEN- and a 9kΩ resistor (R6) from
BEN- to ground. The parallel combination of R5 and R6
should be less than 1kΩ. For typical LVTTL or LVCMOS
specifications of VCC to 2.8V for a high and 0.4V to 0V
for a low, the LVTTL or LVCMOS sources zero current
and sinks a maximum of 720µA ((3.6V to 0V) / 5kΩ).
See Figure 7 for setting up the single-ended LVTTL or
LVCMOS biasing for burst enable.
Applications Information
This section provides an example of how to set up the
MAX3656.
Select Laser
Select a communication-grade laser for the proper data
rate. Assume the laser output average power is PAVG =
0dBm, the operating temperature is -40°C to +85°C,
and the laser diode has the following characteristics:
ZO = 50Ω
ZO = 50Ω
ZO = 50Ω
ZO = 50Ω
VCC
130Ω
IN+
82Ω VCC
130Ω
MAX3656
IN-
82Ω
VCC
130Ω
82Ω VCC
BEN+
130Ω
BEN-
82Ω
ZO = 50Ω
ZO = 50Ω
100Ω
ZO = 50Ω
ZO = 50Ω
100Ω
IN+
IN-
MAX3656
BEN+
BEN-
Figure 5. Connecting to CML Outputs
VCMBEN + (100mV to 800mV)
VCMBEN
VCMBEN - (100mV to 800mV)
3.3V
R1 = 1.65kΩ
VCMBEN = +2.0V
R2 = 2.54kΩ
IN+
IN-
BEN+
BEN-
MAX3656
Figure 4. Connecting to PECL Outputs
Figure 6. Single-Ended Biasing for Burst Enable
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