MAX3296CGILEVKIT Maxim Integrated, MAX3296CGILEVKIT Datasheet - Page 15

• Manufacturer Part Number: MAX3296CGILEVKIT
• Description: Power Management IC Development Tools
• Manufacturer: Maxim Integrated
• Series: MAX3286, MAX3287, MAX3288, MAX3289, MAX3296, MAX3297, MAX3298, MAX3299r

The relationship between laser bias current and R
is shown in Figure 11. The remaining discrete compo-
nents used with the common cathode without photodi-
ode configuration are as follows:
Q1 = general-purpose PNP,
B1 = ferrite bead (see the Bias Filter section)
M1 = general-purpose PMOS device (optional)
C
In the common-anode configuration with photodiode, a
servo control loop is formed by an external NPN transis-
tor (Q1), the laser diode, the monitor diode, R
the power-control amplifier. The voltage at MD is stabi-
lized to 1.7V. The monitor photodiode current is set by
I
itor current (I
Figure 11. Common Cathode without Photodiode Laser
Figure 12. Common Anode with Photodiode
D
BIASDRV
= V
MD
/ R
= 0.1µF (typ)
100
0.1
10
SET
D
1
), then select R
10
(Figure 12). Determine the desired mon-
MAX3286
MAX3289
MAX3296
MAX3299
______________________________________________________________________________________
Common Anode with Photodiode
100
MONITOR
R
DIODE
MON
R
SET
SET
( )
>100, f
V
CC
= 1.7V / I
1k
V
I
CC
D
R
R
SET
MD
t
POL
POL
MD
= 5k
= 1k
MAX3286/96
> 5MHz
3.0V to 5.5V, 1.25Gbps/2.5Gbps
D
ONLY
.
10k
SET
SMOOTH-
, and
START
MON
1.7V
C
connected to the bias transistor (in this case NPN) to
obtain the desired APC loop time constant. This
improves power-supply (and ground) noise rejection. A
capacitance of 0.1µF is sufficient to obtain time con-
stants of up to 5µs in most cases. The voltage across
R
current.
The discrete components used with the common anode
with photodiode configuration are summarized as follows:
R
C
R
Q1 = general-purpose NPN,
B1 = ferrite bead (see the Bias Filter section)
M1 = general-purpose PMOS (optional)
A capacitor can be added to PORDLY to increase the
delay for which POR is asserted low (meaning that V
is within the operational range) when powering up the
part.
The delay is approximately:
See the Typical Operating Characteristics.
DEG
SET
DEG
BIASDRV
BIASDRV
POWER-CONTROL
AMPLIFIER
= 1.7 / I
should not be larger than 250mV at maximum bias
= 0.25 / I
SHDNDRV
BIASDRV
= 0.1µF (typ)
and a degeneration resistor (R
LAN Laser Drivers
MON
D
BIAS(MAX)
V
CC
t
I
BIAS
LASER
C
1 4 10
V
PORDLY
CC
Q1
Programming POR Delay
.
FERRITE
BEAD
B1
R
DEG
C
6
> 100, f
BIASDRV
s
t
> 5MHz
DEG
) must be
CC
15