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

Features

o SFP Reference Design Available
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

MAX3735/MAX3735A

2.7Gbps, Low-Power SFP Laser Drivers

________________________________________________________________ Maxim Integrated Products

Ordering Information

IN+

0.1

µF

GND

MODSET

APCSET

APCFILT2

APCFILT1

SHUTDOWN

TX_FAULT

TX_DISABLE

BC_MON

PC_MON

BIAS

OUT+

OUT-

OPTIONAL SHUTDOWN

CIRCUITRY

IN-

REPRESENTS A CONTROLLED-IMPEDANCE TRANSMISSION LINE

SERDES

MAX3735

MAX3735A

0.1

µF

+3.3V

FERRITE BEAD

+3.3V

BC_MON

PC_MON

0.01

µF

DS1858/DS1859

CONTROLLER

APC

M0N2

M0N3

MON1

+3.3V

Typical Application Circuit

19-2529; Rev 1; 4/03

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.

*Dice are designed to operate from -40°C to +85°C, but are
tested and guaranteed only at T

= +25°C.

**EP = Exposed pad.

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**

Pin Configuration appears at end of data sheet.

EVALUATION KIT

AVAILABLE

MAX3735/MAX3735A

2.7Gbps, Low-Power SFP Laser Drivers

_______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

= +2.97V to +3.63V, T

= -40°C to +85°C. Typical values at V

= +3.3V, I

BIAS

= 20mA, I

MOD

= 30mA, T

= +25°C, unless

otherwise noted.) (Note 1)

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.

Supply Voltage, V

..............................................-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

+ 0.5V)

Voltage at BIAS, PC_MON, BC_MON,

MODSET, APCSET .................................-0.5V to (V

+ 0.5V)

Voltage at OUT+, OUT-.............................+0.5V to (V

+ 1.5V)

Voltage at APCFILT1, APCFILT2 ..............................-0.5V to +3V

Continuous Power Dissipation (T

= +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

)......-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

PARAMETER

SYM B O L

CONDITIONS

MIN

TYP

MAX

UNITS

POWER SUPPLY

Power-Supply Current

Excludes the laser bias and modulation
currents (Note 2)

I/O SPECIFICATIONS

Differential Input Voltage

= (V

+) - (V

-), Figure 1

200

2400

P-P

Common-Mode Input Voltage

0.6

× V

Differential Input Resistance

100

115

TX_DISABLE Input Pullup
Resistance

PULL

4.7

7.4

10.0

HIGH

= V

TX_DISABLE Input Current

LOW

= GND, V

= 3.3V, R

PULL

= 7.4k

-450

µA

TX_DISABLE Input High Voltage

TX_DISABLE Input Low Voltage

0.8

TX_FAULT Output High Voltage

= 100µA sourcing (Note 3)

2.4

TX_FAULT Output Low Voltage

= 1mA sinking (Note 3)

0.4

SHUTDOWN Output High Voltage

= 100µA sourcing

- 0.4

SHUTDOWN Output Low Voltage

= 100µA sinking

0.4

BIAS GENERATOR

Bias On-Current Range

BIAS

Current into BIAS pin

100

Bias Off-Current

BIASOFF

Current into BIAS pin during TX_FAULT or
TX_DISABLE

100

µA

Bias Overshoot

During SFP module hot plugging
(Notes 4, 5, 11)

External resistor to GND defines the voltage
gain, I

BIAS

= 1mA, R

BC_MON

= 69.28k

10.0

13.5

Bias-Current Monitor Gain

BC_MON

BIAS

= 100mA, R

BC_MON

= 693.25

11.5

13.5

mA/A

MAX3735

-8

Bias-Current Monitor Gain
Stability

1mA

BIAS

100mA

(Notes 4, 6)

MAX3735A

-6

MAX3735/MAX3735A

2.7Gbps, Low-Power SFP Laser Drivers

_______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

= +2.97V to +3.63V, T

= -40°C to +85°C. Typical values at V

= +3.3V, I

BIAS

= 20mA, I

MOD

= 30mA, T

= +25°C, unless

otherwise noted.) (Note 1)

PARAMETER

SYM B O L CONDITIONS

MIN

TYP

MAX

UNITS

AUTOMATIC POWER-CONTROL LOOP

MD Reverse Bias Voltage

18µA

1500µA

1.6

MD Average Current Range

Average current into MD pin

1500

µA

BIAS

= 1mA

(MAX3735)

-880

+880

BIA S

= 1m A

( M AX 3735A)

-110

+110

Average Power-Setting Stability

APC closed loop
(Notes 4, 7)

BIA S

= 100m A

-650

+650

ppm/°C

Average Power Setting Accuracy

APC Closed Loop
1mA

BIAS

100mA (Note 8)

-16

+16

MAX3735

0.8

1.23

External resistor to GND
defines the voltage gain;
I

= 18µA, R

PC_MON

50k

MAX3735A

0.9

1.1

MD-Current Monitor Gain

PC_MON

= 1.5mA, R

PC_MON

= 600

0.95

1.05

A/A

MAX3735

-10

+10

MD-Current Monitor Gain Stability

18µA

1500µA

(Notes 4, 6)

MAX3735A

-4

LASER MODULATOR

Current into OUT+ pin; R

15, V

OUT+

OUT-

0.6V (DC-coupled)

Modulation On-Current Range

MOD

Current into OUT+ pin; R

15_, V

OUT+

OUT-

2.0V (AC-coupled)

Modulation Off-Current

MODOFF

Current into OUT+ pin during TX_FAULT or
TX_DISABLE

100

µA

MOD

= 10mA

-480

+480

Modulation-Current Stability
(Note 4)

MOD

= 60mA

-255

+255

ppm/°C

Modulation-Current Absolute
Accuracy

10mA

MOD

60mA (Note 8)

-15

+15

Modulation-Current Rise Time

20% to 80%, 10mA

MOD

60mA (Note 4)

Modulation-Current Fall Time

20% to 80%, 10mA

MOD

60mA (Note 4)

10mA

MOD

60mA at 2.67Gbps

(Notes 4, 9, 10)

At 1.25Gbps (K28.5 pattern)

11.5

At 622Mbps (Note 9)

Deterministic Jitter

At 155Mbps (Note 9)

Random Jitter

10mA

MOD

60mA (Note 4)

0.7

1.0

RMS

MAX3735/MAX3735A

2.7Gbps, Low-Power SFP Laser Drivers

_______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

= +2.97V to +3.63V, T

= -40°C to +85°C. Typical values at V

= +3.3V, I

BIAS

= 20mA, I

MOD

= 30mA, T

= +25°C, unless

otherwise noted.) (Note 1)

Note 1: Specifications at -40°C are guaranteed by design and characterization. Dice are tested at T

= +25°C only.

Note 2:

Maximum value is specified at I

MOD

= 60mA, I

BIAS

= 100mA.

Note 3:

TX_FAULT is an open-collector output and must be pulled up with a 4.7k

to 10k resistor.

Note 4:

Guaranteed by design and characterization.

Note 5:

turn-on time must be

0.8s, DC-coupled interface.

Note 6:

Gain stability is defined by the digital diagnostic document (SFF-8472, rev. 9.0) over temperature and supply variation.

Note 7:

Assuming that the laser diode to photodiode transfer function does not change with temperature.

Note 8:

Accuracy refers to part-to-part variation.

Note 9:

Deterministic jitter is measured using a 2

- 1 PRBS or equivalent pattern.

Note 10: 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).

PARAMETER

SYM B O L CONDITIONS

MIN

TYP

MAX

UNITS

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

1.22

1.30

1.39

Excessive MD-Current
Comparator Threshold Range

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

SFP TIMING REQUIREMENTS

TX_DISABLE Assert Time

t_off

Time from rising edge of TX_DISABLE to
I

BIAS

= I

BIASOFF

and I

MOD

= I

MODOFF

(Note 4)

0.14

µs

APC

= 2.7nF,

MAX3735 (Note 4)

TX_DISABLE Negate Time

t_on

Time from falling edge
of TX_DISABLE to
I

BIAS

and I

MOD

at 95%

of steady state when
TX_FAULT = 0 before
reset

MAX3735A
(Note 11)

600

µs

TX_DISABLE Negate Time
During FAULT Recovery

t_onFAULT

Time from falling edge of TX_DISABLE to
I

BIAS

and I

MOD

at 95% of steady state when

TX_FAULT = 1 before reset (Note 4)

200

TX_FAULT Reset Time or Power-
On Time

t_init

From power-on or negation of TX_FAULT
using TX_DISABLE (Note 4)

200

TX_FAULT Assert Time

t_fault

Time from fault to TX_FAULT on, C

FAULT

20pF, R

FAULT

= 4.7k

(Note 4)

3.3

µs

TX_DISABLE to Reset

Time TX_DISABLE must be held high to
reset TX_FAULT (Note 4)

µs

MAX3735/MAX3735A

2.7Gbps, Low-Power SFP Laser Drivers

_______________________________________________________________________________________

OUT

+) - (V

OUT

(200mV

P-P

min,

2400mV

P-P

max)

(100mV min,
1200mV max)

MOD

VOLTAGE

CURRENT

TIME

OUT

Figure 2. Output Termination for Characterization

0.5pF

OSCILLOSCOPE

OUT+

OUT

OUT-

OUT+

MAX3735

MAX3735A

Figure 1. Required Input Signal and Output Polarity

SOURCE

NOISE

TO LASER

DRIVER V

OPTIONAL

MODULE

HOST BOARD

C1
0.1

µF

C2
10

µF

C3
0.1

µF

µH

VOLTAGE

SUPPLY

FILTER DEFINED BY SFP MSA

Figure 3. Supply Filter

Part Number MAX3735A