MAX3930E/D Maxim Integrated, MAX3930E/D Datasheet - Page 10

• Manufacturer Part Number: MAX3930E/D
• Description: Laser Drivers
• Manufacturer: Maxim Integrated

10.7Gbps Laser Diode Drivers
Table 1. Optical Power Relations
Note: Assuming a 50% average input duty cycle and mark
density.
Figure 3. Optical Power Relations
To program the desired laser bias current, connect the
inverting input of an operational amplifier (such as the
MAX480) to BIASMON, and connect the output to
BIASSET. Connect the positive op amp voltage supply
to V
tion, V
tion, V
current is set by connecting a reference voltage, V
to the noninverting input of the operational amplifier.
Refer to the I
Operating Characteristics to select the value of V
that corresponds to the required laser bias current.
Refer to Maxim Application Note HFAN-2.0, Interfacing
Maxim Laser Drivers with Laser Diodes, for detailed
information.
10
Average Power
Extinction Ratio
Optical Power of a “1”
Optical Power of a “0”
Optical Amplitude
Laser Slope Efficiency
Modulation Current
CC
PARAMETER
______________________________________________________________________________________
OPTICAL
POWER
CC
CC
and the negative supply to V
P
AVG
= 5V and V
P1
P0
= ground and V
BIAS
Programming the Bias Current
Interfacing with Laser Diodes
vs. V
EE
SYM B O L
P
I
= ground; and for -5.2V opera-
P
MOD
AVG
P
P
r
P-P
η
e
BIAS
1
0
EE
= -5.2V). The laser bias
graph in the Typical
P
r
P
P
P
2P
η = P
I
MOD
e
AVG
1
0
P-P
= P
AVG
= 2P
= 2P
= P
P-P
= P
= (P
1
EE
(r
RELATION
/ P
AVG
AVG
e
1
P-P
/ I
- 1) / (r
0
(for 5V opera-
0
- P
MOD
+ P
/ (r
/ η
r
0
e
=
/ (r
e
TIME
1
) / 2
+ 1)
e
e
+ 1)
+ 1)
BIAS
BIAS
,
To minimize optical output aberrations caused by sig-
nal reflections at the electrical interface to the laser
diode, a series damping resistor (R
(Figure 4). The MAX3930/MAX3932 modulation outputs
are optimized for a 20Ω load; therefore, the series com-
bination of R
diode resistance) should equal 20Ω. Typical values for
R
series damping resistor R
For best performance, a bypass capacitor (C), typically
0.01µF, should be placed as close as possible to the
anode of the laser diode.
In some applications (depending on the laser diode
parasitic inductance), an RF matching network at the
laser cathode will improve the optical output.
For high current density and reliable operation, the
MAX3930/MAX3931/MAX3932 use gold metalization.
Make connections to the die with gold wire only, using
ball-bonding techniques. Do not use wedge bonding.
Die-pad size is 3.0mil (76µm) and 4.5mil (114µm). Die
thickness is 8mil (203µm). Die size is 46mil x 82mil
(1.168mm x 2.083mm).
To minimize inductance, keep the connections between
the driver output and the laser diode as short as possi-
ble. Optimize the laser diode performance by placing a
bypass capacitor as close as possible to the laser
anode. Use good high-frequency layout techniques
and multilayer boards with an uninterrupted ground
plane to minimize EMI and crosstalk. Use controlled
impedance lines for the clock and data inputs.
Using the MAX3930/MAX3931/MAX3932 laser driver
alone does not ensure that a transmitter design is com-
pliant with IEC 825. The entire transmitter circuit and
component selections must be considered. Customers
must determine the level of fault tolerance required by
their application, recognizing that Maxim products are
not designed or 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 where the failure of a Maxim prod-
uct could create a situation where personal injury or
death may occur.
D
are 13Ω to 17Ω. The MAX3931 includes an on-chip
D
and R
Applications Information
L
Laser Safety and IEC 825
(where R
D
Layout Considerations
at 15Ω (Figure 5).
L
Wire Bonding Die
represents the laser
D
) is required