19-2529; Rev 2; 7/04
KIT
ATION
EVALU
BLE
AVAILA
2.7Gbps, Low-Power SFP Laser Drivers
General Description
Features
♦
SFP Reference Design Available
♦
Fully Compliant with SFP and SFF-8472 MSAs
♦
Programmable Modulation Current from 10mA to
60mA (DC-Coupled)
♦
Programmable Modulation Current from 10mA to
85mA (AC-Coupled)
♦
Programmable Bias Current from 1mA to 100mA
♦
Edge Transition Times <51ps
♦
27mA (typ) Power-Supply Current
♦
Multirate 155Mbps to 2.7Gbps Operation
♦
Automatic Average Power Control
♦
On-Chip Pullup Resistor for TX_DISABLE
♦
24-Pin 4mm
×
4mm QFN package
MAX3735/MAX3735A
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.
Ordering Information
PART
MAX3735E/D
MAX3735ETG
MAX3735EGG
MAX3735AETG
MAX3735AETG+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
Dice*
24 Thin QFN-EP**
24 QFN-EP**
24 Thin QFN-EP**
24 Thin QFN-EP**
Applications
Gigabit Ethernet SFP/SFF Transceiver Modules
1G/2G Fibre Channel SFP/SFF Transceiver
Modules
Multirate OC3 to OC48-FEC SFP/SFF Transceiver
Modules
*Dice
are designed to operate from -40°C to +85°C, but are
tested and guaranteed only at T
A
= +25°C.
**EP
= Exposed pad.
+Denotes
lead-free package.
Pin Configuration appears at end of data sheet.
Typical Application Circuit
+3.3V
OPTIONAL SHUTDOWN
CIRCUITRY
+3.3V
TX_DISABLE
TX_FAULT
SHUTDOWN
V
CC
15Ω
OUT-
+3.3V
10Ω
0.01µF
0.1µF
IN+
SERDES
0.1µF
IN-
OUT+
OUT+
BIAS
FERRITE BEAD
MAX3735
MAX3735A
APCFILT1
APCFILT2
BC_MON
PC_MON
MODSET
APCSET
GND
MD
C
MD
DS1858/DS1859
H0
CONTROLLER
IC
H1
MON1
M0N2
M0N3
+3.3V
C
APC
R
BC_MON
R
PC_MON
REPRESENTS A CONTROLLED-IMPEDANCE TRANSMISSION LINE
________________________________________________________________
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.
2.7Gbps, Low-Power SFP Laser Drivers
MAX3735/MAX3735A
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V
CC
..............................................-0.5V to +6.0V
Current into BIAS, OUT+, OUT- ......................-20mA to +150mA
Current into MD.....................................................-5mA to +5mA
Voltage at IN+, IN-, TX_DISABLE, TX_FAULT,
SHUTDOWN ...........................................-0.5V to (V
CC
+ 0.5V)
Voltage at BIAS, PC_MON, BC_MON,
MODSET, APCSET .................................-0.5V to (V
CC
+ 0.5V)
Voltage at OUT+, OUT-.............................+0.5V to (V
CC
+ 1.5V)
Voltage at APCFILT1, APCFILT2 ..............................-0.5V to +3V
Continuous Power Dissipation (T
A
= +85°C )
24-Lead Thin QFN (derate 20.8mW/°C
above +85°C).............................................................1354mW
24-Lead QFN (derate 20.8mW/°C
above +85°C).............................................................1354mW
Operating Ambient Temperature Range (T
A
)......-40°C to +85°C
Storage Ambient Temperature Range...............-55°C to +150°C
Die Attach Temperature...................................................+400°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= +2.97V to +3.63V, T
A
= -40°C to +85°C. Typical values at V
CC
= +3.3V, I
BIAS
= 20mA, I
MOD
= 30mA, T
A
= +25°C, unless
otherwise noted.) (Note 1)
PARAMETER
POWER SUPPLY
Power-Supply Current
I/O SPECIFICATIONS
Differential Input Voltage
Common-Mode Input Voltage
Differential Input Resistance
TX_DISABLE Input Pullup
Resistance
TX_DISABLE Input Current
TX_DISABLE Input High Voltage
TX_DISABLE Input Low Voltage
TX_FAULT Output High Voltage
TX_FAULT Output Low Voltage
SHUTDOWN Output High Voltage
SHUTDOWN Output Low Voltage
BIAS GENERATOR
Bias On-Current Range
Bias Off-Current
Bias Overshoot
I
BIAS
I
BIASOFF
Current into BIAS pin
Current into BIAS pin during TX_FAULT or
TX_DISABLE
During SFP module hot plugging
(Notes 4, 5, 11)
I
BC_MON
External resistor to GND defines the voltage
gain, I
BIAS
= 1mA, R
BC_MON
= 69.28kΩ
I
BIAS
= 100mA, R
BC_MON
= 693.25Ω
Bias-Current Monitor Gain
Stability
1mA
≤
I
BIAS
≤
100mA
(Notes 4, 6)
MAX3735
MAX3735A
10.0
11.5
-8
-6
12
13
1
100
100
10
13.5
13.5
+8
+6
%
mA
µA
%
V
IH
V
IL
V
OH
V
OL
V
OH
V
OL
I
OH
= 100µA sourcing (Note 3)
I
OL
= 1mA sinking (Note 3)
I
OH
= 100µA sourcing
I
OL
= 100µA sinking
V
CC
- 0.4
0.4
2.4
0.4
R
PULL
V
HIGH
= V
CC
V
LOW
= GND, V
CC
= 3.3V, R
PULL
= 7.4kΩ
2
0.8
-450
85
4.7
V
ID
V
ID
= (V
IN
+) - (V
IN
-), Figure 1
200
0.6
×
V
CC
100
7.4
2400
115
10.0
15
mV
P-P
V
Ω
kΩ
µA
V
V
V
V
V
V
I
CC
Excludes the laser bias and modulation
currents (Note 2)
27
50
mA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Bias-Current Monitor Gain
mA/A
2
_______________________________________________________________________________________
2.7Gbps, Low-Power SFP Laser Drivers
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +2.97V to +3.63V, T
A
= -40°C to +85°C. Typical values at V
CC
= +3.3V, I
BIAS
= 20mA, I
MOD
= 30mA, T
A
= +25°C, unless
otherwise noted.) (Note 1)
PARAMETER
MD Reverse Bias Voltage
MD Average Current Range
I
MD
SYMBOL
CONDITIONS
18µA
≤
I
MD
≤
1500µA
Average current into MD pin
I
BIAS
= 1mA
(MAX3735)
Average Power-Setting Stability
APC closed loop
(Notes 4, 7)
I
BIAS
= 1mA
(MAX3735A)
I
BIAS
= 100mA
Average Power Setting Accuracy
APC Closed Loop
1mA
≤
I
BIAS
≤
100mA (Note 8)
External resistor to GND
defines the voltage gain;
I
MD
= 18µA, R
PC_MON
=
50kΩ
MAX3735
MAX3735A
MIN
1.6
18
-880
-110
-650
-16
0.8
0.9
0.95
-10
-4
1
1
1500
+880
+110
+650
+16
1.23
1.1
1.05
+10
+4
%
A/A
%
ppm/°C
TYP
MAX
UNITS
V
µA
MAX3735/MAX3735A
AUTOMATIC POWER-CONTROL LOOP
MD-Current Monitor Gain
I
PC_MON
I
MD
= 1.5mA, R
PC_MON
= 600Ω
MD-Current Monitor Gain Stability
LASER MODULATOR
Current into OUT+ pin; R
L
≤
15Ω, V
OUT+
,
V
OUT-
≥
0.6V (DC-coupled)
Current into OUT+ pin; R
L
≤
15Ω_, V
OUT+
,
V
OUT-
≥
2.0V (AC-coupled)
Current into OUT+ pin during TX_FAULT or
TX_DISABLE
I
MOD
= 10mA
I
MOD
= 60mA
10mA
≤
I
MOD
≤
60mA (Note 8)
t
R
t
F
20% to 80%, 10mA
≤
I
MOD
≤
60mA (Note 4)
20% to 80%, 10mA
≤
I
MOD
≤
60mA (Note 4)
10mA
≤
I
MOD
≤
60mA at 2.67Gbps
(Notes 4, 9, 10)
Deterministic Jitter
At 1.25Gbps (K28.5 pattern)
At 622Mbps (Note 9)
At 155Mbps (Note 9)
Random Jitter
RJ
10mA
≤
I
MOD
≤
60mA (Note 4)
18µA
≤
I
MD
≤
1500µA
(Notes 4, 6)
MAX3735
MAX3735A
10
10
60
mA
85
100
µA
ppm/°C
%
ps
ps
Modulation On-Current Range
I
MOD
Modulation Off-Current
Modulation-Current Stability
(Note 4)
Modulation-Current Absolute
Accuracy
Modulation-Current Rise Time
Modulation-Current Fall Time
I
MODOFF
-480
-255
-15
42
50
18
11.5
18
40
0.7
+480
+255
+15
65
80
38
ps
1.0
ps
RMS
_______________________________________________________________________________________
3
2.7Gbps, Low-Power SFP Laser Drivers
MAX3735/MAX3735A
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +2.97V to +3.63V, T
A
= -40°C to +85°C. Typical values at V
CC
= +3.3V, I
BIAS
= 20mA, I
MOD
= 30mA, T
A
= +25°C, unless
otherwise noted.) (Note 1)
PARAMETER
SAFETY FEATURES
Excessive Bias-Current
Comparator Threshold Range
TX_FAULT always occurs for V
BC_MON
≥
1.38V, TX_FAULT never occurs for
V
BC_MON
≤
1.22V
TX_FAULT always occurs for V
PC_MON
≥
1.38V, TX_FAULT never occurs for
V
PC_MON
≤
1.22V
1.22
1.30
1.39
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Excessive MD-Current
Comparator Threshold Range
SFP TIMING REQUIREMENTS
TX_DISABLE Assert Time
t_off
1.22
1.30
1.39
V
Time from rising edge of TX_DISABLE to
I
BIAS
= I
BIASOFF
and I
MOD
= I
MODOFF
(Note 4)
Time from falling edge
of TX_DISABLE to
I
BIAS
and I
MOD
at 95%
of steady state when
TX_FAULT = 0 before
reset
C
APC
= 2.7nF,
MAX3735 (Note 4)
MAX3735A
(Note 11)
0.14
5
µs
1
ms
TX_DISABLE Negate Time
t_on
600
µs
TX_DISABLE Negate Time
During FAULT Recovery
TX_FAULT Reset Time or Power-
On Time
TX_FAULT Assert Time
TX_DISABLE to Reset
Time from falling edge of TX_DISABLE to
t_onFAULT I
BIAS
and I
MOD
at 95% of steady state when
TX_FAULT = 1 before reset (Note 4)
t_init
t_fault
From power-on or negation of TX_FAULT
using TX_DISABLE (Note 4)
Time from fault to TX_FAULT on, C
FAULT
≤
20pF, R
FAULT
= 4.7kΩ (Note 4)
Time TX_DISABLE must be held high to
reset TX_FAULT (Note 4)
60
200
ms
60
3.3
200
50
5
ms
µs
µs
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Specifications at -40°C are guaranteed by design and characterization. Dice are tested at T
A
= +25°C only.
Maximum value is specified at I
MOD
= 60mA, I
BIAS
= 100mA.
TX_FAULT is an open-collector output and must be pulled up with a 4.7kΩ to 10kΩ resistor.
Guaranteed by design and characterization.
V
CC
turn-on time must be
≤
0.8s, DC-coupled interface.
Gain stability is defined by the digital diagnostic document (SFF-8472, rev. 9.0) over temperature and supply variation.
Assuming that the laser diode to photodiode transfer function does not change with temperature.
Accuracy refers to part-to-part variation.
Deterministic jitter is measured using a 2
23
- 1 PRBS or equivalent pattern.
Broadband noise is filtered through the network as shown in Figure 3. One capacitor,
C < 0.47µF, and one 0603 ferrite bead or inductor can be added (optional). This supply voltage filtering reduces the hot-
plugging inrush current. The supply noise must be < 100mV
P-P
up to 2MHz.
Note 11:
C
APC
values chosen as shown in Table 4 (MAX3735A).
4
_______________________________________________________________________________________
2.7Gbps, Low-Power SFP Laser Drivers
MAX3735/MAX3735A
V
CC
V
CC
VOLTAGE
V
IN
+
V
IN
-
(100mV min,
1200mV max)
30Ω
30Ω
MAX3735
MAX3735A
OUT-
30Ω
0.5pF
(V
IN
+) - (V
IN
-)
(200mV
P-P
min,
2400mV
P-P
max)
CURRENT
I
OUT
+
I
MOD
OUT+
OUT+
I
OUT
+
OSCILLOSCOPE
75Ω
50Ω
TIME
Figure 1. Required Input Signal and Output Polarity
Figure 2. Output Termination for Characterization
HOST BOARD
FILTER DEFINED BY SFP MSA
SOURCE
NOISE
VOLTAGE
SUPPLY
C1
0.1µF
C2
10µF
L1
1µH
C3
0.1µF
MODULE
TO LASER
DRIVER V
CC
OPTIONAL
OPTIONAL
Figure 3. Supply Filter
_______________________________________________________________________________________
5
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