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PDF MAX3735 Data sheet ( Hoja de datos )
| Número de pieza | MAX3735 | |
| Descripción | 2.7Gbps / Low-Power SFP Laser Drivers | |
| Fabricantes | Maxim Integrated | |
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19-2529; Rev 1; 4/03
EVAALVUAAILTAIOBNLEKIT
2.7Gbps, Low-Power SFP Laser Drivers
General Description
The MAX3735/MAX3735A are +3.3V laser drivers for
SFP/SFF applications from 155Mbps up to 2.7Gbps.
The devices accept differential input data and provide
bias and modulation currents for driving a laser. DC-
coupling to the laser allows for multirate applications
and reduces the number of external components. The
MAX3735/MAX3735A are fully compliant with the SFP
MSA timing and the SFF-8472 transmit diagnostic
requirements.
An automatic power-control (APC) feedback loop is incor-
porated to maintain a constant average optical power
over temperature and lifetime. The wide modulation cur-
rent range of 10mA to 60mA (up to 85mA AC-coupled)
and bias current of 1mA to 100mA make this product
ideal for driving FP/DFB laser diodes in fiber-optic mod-
ules. The resistor range for the laser current settings is
optimized to interface with the DS1858 SFP controller IC.
The MAX3735/MAX3735A provide transmit-disable con-
trol, a single-point latched transmit-failure monitor out-
put, photocurrent monitoring, and bias-current
monitoring to indicate when the APC loop is unable to
maintain the average optical power. The MAX3735A
also features improved multirate operation.
The MAX3735/MAX3735A come in package and die
form, and operate over the extended temperature
range of -40°C to +85°C.
Applications
Gigabit Ethernet SFP/SFF Transceiver Modules
1G/2G Fibre Channel SFP/SFF Transceiver
Modules
Multirate OC3 to OC48-FEC SFP/SFF Transceiver
Modules
o SFP Reference Design Available
Features
o Fully Compliant with SFP and SFF-8472 MSAs
o Programmable Modulation Current from 10mA to
60mA (DC-Coupled)
o Programmable Modulation Current from 10mA to
85mA (AC-Coupled)
o Programmable Bias Current from 1mA to 100mA
o Edge Transition Times <51ps
o 27mA (typ) Power-Supply Current
o Multirate 155Mbps to 2.7Gbps Operation
o Automatic Average Power Control
o On-Chip Pullup Resistor for TX_DISABLE
o 24-Pin 4mm × 4mm QFN package
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX3735E/D
-40°C to +85°C
Dice*
MAX3735ETG
-40°C to +85°C
24 Thin QFN-EP**
MAX3735EGG
-40°C to +85°C
24 QFN-EP**
MAX3735AETG -40°C to +85°C
24 Thin QFN-EP**
*Dice are designed to operate from -40°C to +85°C, but are
tested and guaranteed only at TA = +25°C.
**EP = Exposed pad.
Pin Configuration appears at end of data sheet.
Typical Application Circuit
+3.3V
+3.3V
OPTIONAL SHUTDOWN
CIRCUITRY
SERDES
0.1µF
0.1µF
IN+
IN-
DS1858/DS1859
CONTROLLER
H0
IC H1
MON1
M0N2
M0N3
+3.3V
MAX3735
MAX3735A
OUT-
OUT+
OUT+
BIAS
MD
+3.3V
15Ω
10Ω
FERRITE BEAD
CMD
CAPC
RBC_MON
RPC_MON
REPRESENTS A CONTROLLED-IMPEDANCE TRANSMISSION LINE
0.01µF
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
2.7Gbps, Low-Power SFP Laser Drivers
VOLTAGE
VOUT+
VOUT-
(VIN+) - (VIN-)
CURRENT
IOUT+
(100mV min,
1200mV max)
(200mVP-P min,
2400mVP-P max)
IMOD
TIME
Figure 1. Required Input Signal and Output Polarity
VCC VCC
30Ω
MAX3735
MAX3735A
OUT-
0.5pF
30Ω
30Ω
OUT+
OUT+
IOUT+
OSCILLOSCOPE
75Ω 50Ω
Figure 2. Output Termination for Characterization
SOURCE
NOISE
VOLTAGE
SUPPLY
HOST BOARD
FILTER DEFINED BY SFP MSA
L1
1µH
MODULE
OPTIONAL
TO LASER
DRIVER VCC
C1
0.1µF
C2
10µF
C3
0.1µF
OPTIONAL
Figure 3. Supply Filter
_______________________________________________________________________________________ 5
5 Page 
2.7Gbps, Low-Power SFP Laser Drivers
VCC
TX_DISABLE
PC_MON
RPC_MON
BC_MON
RBC_MON
POR AND COUNTER
FOR t_init
COUNTER FOR
t_onfault
VCC
IMD VBG
1
VCC
COMP
IBIAS VBG
76
MODSET
SHORT-
CIRCUIT
DETECTOR
COMP
MAX3735
MAX3735A
100ns DELAY
IMOD
ENABLE
IBIAS
ENABLE
RQ
RS
LATCH
S
SHUTDOWN
CMOS
TX_FAULT
TTL
OPEN COLLECTOR
Figure 5. Safety Circuitry
Table 1. Typical Fault Conditions
If any of the I/O pins is shorted to GND or VCC (single-
1. point failure, see Table 2), and the bias current or the
photocurrent exceed the programmed threshold.
End-of-life (EOL) condition of the laser diode. The bias
2. current and/or the photocurrent exceed the
programmed threshold.
3. Laser cathode is grounded and the photocurrent
exceeds the programmed thresholds.
No feedback for the APC loop (broken interconnection,
4. defective monitor photodiode), and the bias current
exceeds the programmed threshold.
Design Procedure
When designing a laser transmitter, the optical output
usually is expressed in terms of average power and
extinction ratio. Table 3 shows relationships helpful in
converting between the optical average power and the
modulation current. These relationships are valid if the
mark density and duty cycle of the optical waveform
are 50%.
Programming the Modulation Current
For a given laser power (PAVG), slope efficiency (η), and
extinction ratio (re), the modulation current can be calcu-
lated using Table 3. See the Modulation Current vs.
RMODSET graph in the Typical Operating Characteristics
section, and select the value of RMODSET that corre-
sponds to the required current at +25°C.
Programming the APC Loop
Program the average optical power by adjusting -RAPC-
SET. To select the resistance, determine the desired moni-
tor current to be maintained over temperature and
lifetime. See the Monitor Diode Current vs. RAPCSET
graph in the Typical Operating Characteristics section,
and select the value of RAPCSET that corresponds to the
required current.
Interfacing with Laser Diodes
To minimize optical output aberrations caused by sig-
nal reflections at the electrical interface to the laser
diode, a series-damping resistor (RD) is required
(Figure 4). Additionally, the MAX3735/MAX3735A out-
puts are optimized for a 15Ω load. Therefore, the series
combination of RD and RL, where RL represents the
laser-diode resistance, should equal 15Ω. Typical val-
ues for RD are 8Ω to 13Ω. For best performance, place
a bypass capacitor (0.01µF typ) as close as possible to
the anode of the laser diode. An RC shunt network
between the laser cathode and ground minimizes opti-
cal output aberrations. Starting values for most coaxial
lasers are RCOMP = 50Ω in series with CCOMP = 8pF.
Adjust these values experimentally until the optical out-
put waveform is optimized. Refer to Maxim Application
Note: HFAN 02.0: Interfacing Maxim’s Laser Drivers to
Laser Diodes for more information.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet MAX3735.PDF ] | |
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