MAX3996CGP Maxim Integrated Products, MAX3996CGP Datasheet - Page 12

• Manufacturer Part Number: MAX3996CGP
• Description: Laser Driver +3.0V to +5.5V, 2.5G bps VCSEL and Laser
• Manufacturer: Maxim Integrated Products

Specifications of MAX3996CGP

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

monitor photodiode current is set by I
Determine the desired monitor current (I
select R
A bias stabilizing capacitor (C
ed between the COMP pin and ground to obtain the
desired APC loop time constant. This improves power-
supply and ground noise rejection. A capacitance of
0.1µF usually is sufficient to obtain time constants of up
to 35µs.
The degeneration resistance between MON2 and
ground determines the bias current that causes a fault
and affects the APC time constant. Select R
total resistance between MON2 and ground) =
400mV/(maximum bias current). A degeneration resis-
tance of 10Ω can be obtained by grounding MON1.
Increasing R
The discrete components for use with the common
anode with photodiode configuration are:
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
Figure 11. APC Loop
12
______________________________________________________________________________________
SET
*FERRITE BEAD
= 1.1V/I
MON
MONITOR
increases the APC time constant.
DIODE
R
D
SET
.
V
CC
I
D
MD
COMP
SMOOTH
START
) must be connect-
D
= V
D
), and then
1.1V
MD
MON
/R
POWER-CONTROL
SET
(the
AMPLIFIER
MAX3996
.
A capacitor can be added to PORDLY to increase the
delay when powering up the part. The delay will be
approximately:
See the Typical Operating Characteristics section.
Laser package inductance causes the laser impedance
to increase at high frequencies, leading to ringing,
overshoot, and degradation of the laser output. A laser-
compensation filter network can be used to reduce the
laser impedance at high frequencies, thereby reducing
output ringing and overshoot.
R
C
L1 = ferrite bead, see the Bias Filter section
R
SET
MON
COMP
DISABLE
BIAS
Designing the Laser-Compensation
= 1.1V/I
C
= 400mV/(maximum bias current)
0.1µF
COMP
= 0.1µF (typ)
SHUTDOWN
CIRCUIT
t
=
COMP
D
SHDNDRV
1 4 10
C
.
PORDLY
×
Programming POR Delay
11Ω
−
6
sec
SHUTDOWN
CIRCUITRY
OPTIONAL
I
BIAS
onds
Filter Network
BIAS
MON2
MON1
LASER
V
CC
L1*