MAX3643ETG+T Maxim Integrated Products, MAX3643ETG+T Datasheet - Page 12

• Manufacturer Part Number: MAX3643ETG+T
• Description: IC LASR DRVR 2.5GBPS 3.6V 24TQFN
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of MAX3643ETG+T

• Data Rate: 2.5Gbps
• Number Of Channels: 1
• Voltage - Supply: 3 V ~ 3.6 V
• Current - Supply: 32mA
• Current - Modulation: 85mA
• Current - Bias: 70mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 24-TQFN Exposed Pad
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

155Mbps to 2.5Gbps Burst-Mode Laser Driver
This approach can also be used for a conventional volt-
age DAC output, if desired. In all cases, the voltage at
MODSET must be kept ≤ 1.4V, which limits the range of
acceptable values for R
mum modulation current.
Laser diode bias current is set in the same manner as
modulation current.
The MAX3643 data and BEN inputs are biased with an
on-chip, high-impedance network. When DC-coupled,
the MAX3643 operates properly with signals that meet
the EC table input-swing and common-mode require-
ments, including LVPECL and most CML.
See Figure 3 for a termination network that can be used
to connect the data and BEN inputs to LVPECL data out-
puts. Other termination networks may also be used, as
long as both the input swing and common limits are met.
When the MAX3643 internal sample-and-hold is not
required, the MDIN pin should be connected to ground
and the MDOUT pin unconnected. If the internal sample-
and-hold is required, then it is necessary to ensure that
the time constant resulting from the monitor diode load
resistance and the total load capacitance is compatible
with the desired minimum burst interval. It is also neces-
sary to make certain that the load at MDOUT does not
exceed the capability of the MDOUT pin.
Because the voltage at MDIN is not reflected to MDOUT
until after the end of the laser burst, systems using the
internal sample-and-hold alone cannot support continu-
ous mode operation, often a required feature for module
calibration. In this case, the voltage at MDIN can also
be connected directly to a controller mux input. As long
as the total capacitance (including monitor diode intrin-
sic capacitance, MDIN capacitance, mux off-capaci-
tance, and wiring parasitics) is less than 50pF, and the
monitor diode load resistor is less than 2kΩ, then the
sample-and-hold captures a 576ns minimum burst. The
MAX3643 typical MDIN capacitance is 5pF, typical
monitor diode maximum capacitance is 25pF, and the
typical capacitance of a mux input in the off-state is
3pF to 5pF. When the mux is in the on-state, the capac-
itance at the input is typically 10pF to 20pF.
12
______________________________________________________________________________________
LVPECL Data/Burst-Enable Inputs
Sample-and-Hold Operation
MODSET
depending on the maxi-
If the minimum burst duration is longer than 576ns, it
may be useful to connect an external capacitor in par-
allel with the monitor diode load to limit the effects of
the data pattern on the monitor diode output.
Figure 3. LVPECL High-Speed Inputs
Figure 4. Single-Ended Biasing for Burst Enable
LVPECL
V
V
V
CMBEN
CMBEN
CMBEN
+ (100mV to 800mV)
- (100mV to 800mV)
Z
Z
O
O
= 50Ω
= 50Ω
V
CMBEN
130Ω
82Ω
= +2.0V
3.3V
V
130Ω
CC
82Ω
R
R
1
2
= 1.65kΩ
= 2.54kΩ
IN+/BEN+
IN-/BEN-
MAX3643
IN+
IN-
BEN+
BEN-
MAX3643