MAX3735AETG+ Maxim Integrated Products, MAX3735AETG+ Datasheet - Page 13

• Manufacturer Part Number: MAX3735AETG+
• Description: IC LSR DRVR 2.7GBPS 3.63V 24TQFN
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of MAX3735AETG+

• Data Rate: 2.7Gbps
• Number Of Channels: 1
• Voltage - Supply: 2.97 V ~ 3.63 V
• Current - Supply: 27mA
• Current - Modulation: 85mA
• Current - Bias: 100mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 24-TQFN Exposed Pad
• Mounting Type: Surface Mount
• Operating Supply Voltage: 3.3 V
• Supply Current: 27 mA
• Maximum Operating Temperature: + 85 C
• Maximum Power Dissipation: 1354 mW
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX3735/MAX3735A data inputs are SFP MSA
compliant. On-chip 100Ω differential input impedance is
provided for optimal termination (Figure 6). Because of
the on-chip biasing network, the MAX3735/MAX3735A
inputs self-bias to the proper operating point to accom-
modate AC-coupling.
The SHUTDOWN control output features extended eye
safety when the laser cathode is grounded. An external
transistor is required to implement this circuit (Figure 4).
In the event of a fault, SHUTDOWN asserts high, plac-
ing the optional shutdown transistor in cutoff mode and
thereby shutting off the laser current.
An example of how to set up the MAX3735/MAX3735A
follows:
Select a communications-grade laser for 2.488Gbps.
Assume that the laser output average power is P AVG =
0dBm, the operating temperature is -40°C to +85°C,
minimum extinction ratio is 6.6 (8.2dB), and the laser
diode has the following characteristics:
Figure 6. Simplified Input Structure
Wavelength: λ = 1.3µm
Threshold current: I
Threshold temperature coefficient: β
Laser-to-monitor transfer: ρ
Laser slope efficiency: η = 0.05mW/mA at +25°C
0.11pF
0.11pF
IN+
IN-
MAX3735A
Optional Shutdown Output Circuitry
MAX3735
PACKAGE
0.97nH
0.97nH
Input Termination Requirements
Applications Information
______________________________________________________________________________________
2.7Gbps, Low-Power SFP Laser Drivers
TH
V
V
CC
CC
= 22mA at +25°C
50Ω
50Ω
16kΩ
24kΩ
MON
= 0.2A/W
V
CC
TH
= 1.3% / °C
The desired monitor diode current is estimated by I
= P
SET
tion shows that R
also be estimated using the equation below:
To achieve a minimum extinction ratio (r
temperature and lifetime, calculate the required extinc-
tion ratio at +25°C. Assuming the results of the calcula-
tion are r
power P
required modulation current is 1.81mW / (0.05mW/mA)
= 36.2mA. The Modulation Current vs. R
in the Typical Operating Characteristics section shows
that R
estimated using the equation below:
In order to meet SFP timing requirements and minimize
pattern-dependent jitter, the CAPC capacitor value is
determined by the laser-to-monitor transfer and other
variables. The following equations and table can be
used to choose the CAPC values for the MAX3735 and
MAX3735A, respectively. The equations and table
assume a DC-coupled laser. Refer to Maxim
Application Note HFDN 23.0: Choosing the APC Loop
Figure 7. Simplified Output Structure
AVG
graph in the Typical Operating Characteristics sec-
MODSET
x ρ
MAX3735A
P-P
MAX3735
e
I
MOD
MON
= 20 at +25°C, the peak-to-peak optical
= 1.81mW, according to Table 3. The
I
should be 9.5kΩ. The value can also be
MD
= 1.23 / (0.0037 × R
= 200µA. The Monitor Diode vs. R
APCSET
= 1.23 / (2 × R
V
should be 3kΩ. The value can
CC
Determine R
Determine R
APCSET
Determine C
0.81nH
0.99nH
0.99nH
MODSET
PACKAGE
0.11pF
0.11pF
0.11pF
)
MODSET
e
) of 6.6 over
)
MODSET
OUT-
OUT+
OUT+
APCSET
K = 0.3
graph
APC-
APC
MD
13