MAX3766EEP+ Maxim Integrated Products, MAX3766EEP+ Datasheet - Page 12

• Manufacturer Part Number: MAX3766EEP+
• Description: IC LASR DRVR 622MBPS 5.5V 20QSOP
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of MAX3766EEP+

• Data Rate: 622Mbps
• Number Of Channels: 1
• Voltage - Supply: 4.5 V ~ 5.5 V
• Current - Supply: 25mA
• Current - Modulation: 60mA
• Current - Bias: 80mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 20-QSOP
• Mounting Type: Surface Mount
• Operating Supply Voltage: 5 V
• Supply Current: 25 mA
• Maximum Operating Temperature: + 85 C
• Maximum Power Dissipation: 590 mW
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Compute the required modulation tempco from the
slope efficiency of the laser at T
temperature. Then select the value of R
Typical Operating Characteristics.
For example, suppose a laser has a slope efficiency
(SE) of 0.021mW/mA at +25°C, which reduces to
0.018mW/mA at +85°C. The temperature coefficient is
given by the following:
From the Typical Operating Characteristics, the value
for R
modulation temperature compensation is not desired,
connect TC directly to REF1.
The modulation-current amplitude can be programmed
with a fixed resistor or adjusted with a potentiometer. A
small internal resistance is provided to prevent damage
if the potentiometer is adjusted to the end of its range.
The value of R
Operating Characteristics.
Example: A transmitter requires average power of
-8dBm (160µW), with an extinction ratio of 15. The opti-
cal signal output is 280µW (see Optical Power
Relations). If the slope efficiency is 0.021mW/mA at
+25°C, then the required modulation current is
0.280mW / 0.021mW/mA = 13.3mA. From the Typical
Operating Characteristics, the value of R
ed to be 3kΩ.
When APC is used, the average power control is pro-
grammed by R
tiometer. The value of R
from the Typical Operating Characteristics.
Example: Suppose a transmitter’s output power will be
adjusted to -8dBm (160µW) average power during
manufacturing. The coupling efficiency from laser to
monitor photodiode varies from 0.4A/W to 0.8A/W for
the selected laser, causing monitor current to vary
between 64µA and 128µA. From the Typical Operating
Characteristics, R
between 12kΩ and 24kΩ.
622Mbps LAN/WAN Laser Driver with
Automatic Power Control and Safety Shutdown
12
Laser tempco
TC
______________________________________________________________________________________
, which offsets the tempco of the laser, is 3kΩ. If
Set Modulation-Current Tempco
MOD
POWERSET
=
= −
POWERSET
and Maximum Bias Current
can be selected from the Typical
SE
2380ppm C
Set Average Laser Power
(
SE
25
Set Modulation Current
POWERSET
, which is typically a poten-
85
•
(
−
85
A
should be adjustable
/
SE
°
= +25°C and at a hot
−
25
can be estimated
25
)
)
MOD
•
TC
10
is select-
from the
6
Select R
laser at its end of life. For example, if the expected
laser threshold at +85°C and end of life is 40mA, then
from the Typical Operating Characteristics, R
should be 1kΩ or less.
If APC is not used, the laser bias current is pro-
grammed by R
Typical Operating Characteristics.
Capacitor C
must be large enough not to cause data-dependent jit-
ter. For 622Mbps SONET/ATM applications, Maxim rec-
ommends selecting C
When using the latched shutdown configuration, deter-
mine the minimum value of C
Operating Characteristics. Calculate C
For example: If C
rent (I
be 50nF or larger. This ensures that t
10 times the t
To reduce data-dependent jitter, add a filter at BIAS
(see Typical Operating Circuit). Maxim recommends a
1µH inductor or ferrite bead with a self-resonance fre-
quency of 200MHz or more.
Laser package lead inductance causes the laser
impedance to increase at high frequencies, which
leads to ringing, overshoot, and degradation of the out-
put eye. A laser-compensation filter network can be
used to reduce the output load seen by the MAX3766
at high frequencies, thereby reducing output ringing
and overshoot.
The compensation components (R
are most easily determined by experimentation. Begin
with a no-compensation network, and observe the ring
frequency (f
Begin with R
Increase C
obtained.
MD
BIASMAX
) is 100µA, then the value of C
COMP
MD
n
COMP
APC
) of the laser and laser driver (Figure 7).
C
determines the APC time constant, and
SAFETY
BIASMAX
.
to provide sufficient current for a hot
MD
= 25Ω and C
until the desired transmitter eye is
Design Laser-Compensation
MD
is 0.1µF and typical monitor cur-
=
Set APC Time Constant
≥ 0.1µF.
. Select R
20k
SAFETY
Ω
COMP
C
Design Bias Filter
MD
•
Select C
COMP
I
BIASMAX
MD
Filter Network
SAFETY
= 1/(2πf
SAFETY
from the Typical
SAFETY
and C
as follows:
n
is at least
from the
SAFETY
BIASMAX
R
COMP
should
COMP
).
)