MAX3656
155Mbps to 2.5Gbps Burst-Mode
Laser Driver
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Applications Information
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 (R
1
) from V
CC
to BEN- and
resistor (R
2
) from BEN- to ground. The parallel combi-
nation of R
1
and R
2
should be less than 1kΩ. Choose
the values of R
1
and R
2
to set the common-mode volt-
age 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 3kΩ (R
4
) resistor
from the burst-enable signal to BEN+. Connect a 5kΩ
(R
3
) resistor from V
CC
to BEN+. Connect a 5kΩ resistor
(R
5
) from V
CC
to BEN- and a 9kΩ resistor (R
6
) from
BEN- to ground. For typical LVTTL or LVCMOS specifi-
cations of V
CC
to 2.0V for a high and 0.8V to 0V for a
low, the LVTTL or LVCMOS sources a maximum of
75µA and sinks a maximum of 500µA. See Figure 7 for
setting up the single-ended LVTTL or LVCMOS biasing
for burst enable.
Layout Considerations
To minimize inductance, keep the connections between
the MAX3656 output pins and laser diode as close as
possible. Place a bypass capacitor as close as possi-
ble to each V
CC
connection. Take extra care to mini-
mize stray parasitic capacitance on the BIAS and MD
pins. Use good high-frequency layout techniques and
multilayer boards with uninterrupted ground planes to
minimize EMI and crosstalk.
Laser Safety and IEC825
Using the MAX3656 laser driver alone does not ensure
that a transmitter design is compliant with IEC825. The
entire transmitter circuit and component selections
must be considered. Each user must determine the
level of fault tolerance required by the application, rec-
ognizing that Maxim products are neither designed nor
authorized for use as components in systems intended
for surgical implant into the body, for applications
intended to support or sustain life, or for any other
application in which the failure of a Maxim product
could create a situation where personal injury or death
can occur.
Figure 7. Single-Ended LVTTL or LVCMOS Biasing for Burst
Enable
