MAX3296CTI+ Maxim Integrated Products, MAX3296CTI+ Datasheet - Page 12

• Manufacturer Part Number: MAX3296CTI+
• Description: IC LASR DRVR 2.5GBPS 5.5V 28TQFN
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of MAX3296CTI+

• Data Rate: 2.5Gbps
• Number Of Channels: 1
• Voltage - Supply: 3 V ~ 5.5 V
• Current - Supply: 52mA
• Current - Modulation: 30mA
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 28-WFQFN Exposed Pad
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3.0V to 5.5V, 1.25Gbps/2.5Gbps
LAN Laser Drivers
Figure 7. Power-On Reset Circuit
2) EN is switched low, then high.
3) EN is switched to high, then low.
Figure 7 shows the POR circuit for the MAX3286/
MAX3296 series devices. A POR signal asserts low
when V
ing range is determined by the LV pin, as shown in
Table 2. POR contains an internal delay to reject noise
on V
be extended by adding capacitance to the PORDLY
pin. The POR comparator includes hysteresis to improve
noise rejection. The laser driver is shut down while V
is out of the operating range.
Select a communications-grade laser with a rise time of
260ps or better for 1.25Gbps, or 130ps or better for
2.5Gbps applications. To obtain the MAX3286/
MAX3296’s AC specifications, the instantaneous output
voltage at OUT+ must remain above V
times. Select a high-efficiency laser that requires low
modulation current and generates low-voltage swing at
OUT+. Laser package inductance can be reduced by
trimming the leads. Typical package leads have induc-
tance of 25nH/in (1nH/mm); this inductance causes a
larger voltage swing across the laser. A compensation fil-
ter network also can be used to reduce ringing, edge
speed, and voltage swing.
Resistors at the MODSET and TC pins set the ampli-
tude of the modulation current. The resistor R
the temperature-stable portion of the modulation cur-
12
CC
______________________________________________________________________________________
LV
CC
Programming the Modulation Current
during power-on or hot-plugging. The delay can
is in the operating range. The voltage operat-
25k
36k
V
CC
28k
1.2V
BANDGAP
Power-On Reset (POR)
Design Procedure
= 0.7s/ F C
VARIABLE
PORDLY
DELAY
PORDLY
MAX3286
MAX3296
Select Laser
CC
- 1V at all
MOD
POR
sets
CC
rent, while the resistor R
increasing portion of the modulation current.
To determine the appropriate temperature coefficient
from the slope efficiency (
equation:
where
laser current.
For example, suppose a laser has a slope efficiency
0.018mW/mA at +70°C. Using the above equation pro-
duces a laser tempco of -3175ppm/°C.
To obtain the desired modulation current and tempco
for the device, the following two equations can be used
to determine the required values of R
where tempco = -laser tempco.
Figure 8a shows a family of curves derived from these
equations. The straight diagonal lines depict constant
tempcos. The curved lines represent constant modula-
tion currents. If no temperature compensation is
desired, Figure 8b displays a series of curves that
show laser modulation current with respect to R
different loads.
The following useful equations were used to derive
Figure 8a and the equations at the beginning of this
section. The first assumes R
Three application circuits are described below: com-
mon-cathode laser with photodiode, common-cathode
laser without photodiode, and common-anode laser
25
Laser tempco
I
MOD
of 0.021mW/mA at +25°C, which reduces to
R
is the slope of the laser output power to the
MOD
51
Programming the Bias Current/APC
I
(
MOD
tempco
R
(
70
TC
(
R
R
1 4 0
MOD
TC
)(
C
( .
25
0 19 48
70
)
1 15
.
(
tempco I
.
70
70
C
250 52
250
I
–
10
C
MOD
of the laser, use the following
25
TC
0 21
L
.
)
= 25 .
25
3
25
(
C A
sets the temperature-
25
MOD
t
T
empco
)
C
R
–
C
)
t
TC
25
)
empco
MOD
1 06
.
C
10
)
250
250
I
MOD
6
and R
ppm C
(
250
25
MOD
TC
C
/
)
:
A
for