MAX3736ETE+ - MAXIM INTEGRATED PRODUCTS

General Description

The MAX3736 is a compact, +3.3V multirate laser driver

for SFP/SFF applications up to 3.2Gbps. The device

accepts differential data and provides bias and modula-

tion currents for driving a laser. DC-coupling to the laser

allows for multirate applications, and reduces the num-

ber of external components.

The wide 5mA to 60mA (85mA AC-coupled) modulation

current range and 1mA to 100mA bias current make the

MAX3736 ideal for driving FP/DFB laser diodes in fiber-

optic modules. The laser current setting can be con-

trolled by a current DAC, a voltage DAC, or a resistor.

Very low power dissipation, small package size, and

reduced component count, make this part an ideal solu-

tion for SFP-module applications.

The MAX3736 is available in a small 3mm x 3mm, 16-pin

thin QFN package. It operates over a -40°C to +85°C

temperature range.

Applications

Gigabit Ethernet SFP/SFF Transceiver Modules

1G/2G Fibre-Channel SFP/SFF Transceiver

Modules

Multirate OC-3 to OC-48 FEC SFP/SFF

Transceiver Modules

10G Ethernet LX-4 Modules

Features

♦Fully Compatible with SFP and SFF-8472

Specifications

♦Programmable Modulation Current from 5mA to

60mA (DC-Coupled)

♦Programmable Modulation Current from 5mA to

85mA (AC-Coupled)

♦Programmable Bias Current from 1mA to 100mA

♦56ps Edge Transition Times

♦22mA (typ) Power-Supply Current

♦Multirate Operation Up to 3.2Gbps

♦On-Chip Pullup Resistor for DIS

♦16-Pin, 3mm ×3mm Thin QFN Package

MAX3736

3.2Gbps, Low-Power, Compact,

SFP Laser Driver

________________________________________________________________

Maxim Integrated Products

Ordering Information

+3.3V

SUPPLY FILTER

VCC

OUT-

OUT+

BIAS

BIASSET

MODSET

IN+

IN-

MOD-DEF1

MOD-DEF2

TX_DISABLE LASER CONTROLLER

15Ω56Ω

10Ω

8.2pF

0.01μF

FERRITE

BEAD

0.1μF

GND

DIS

SERDES

HOST FILTER

VCC_RX

BC_MON

50Ω

HOST BOARD SFP OPTICAL TRANSMITTER

MAX3736

Typical Application Circuit

19-3116; Rev 2; 9/10

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

Denotes a lead(Pb)-free/RoHS-compliant package.

EP = Exposed pad.

PART TEMP RANGE PIN-PACKAGE

MAX3736ETE -40°C to +85°C 16 Thin QFN-EP*

MAX3736ETE+ -40°C to +85°C 16 Thin QFN-EP*

Pin Configuration appears at end of data sheet.

MAX3736

3.2Gbps, Low-Power, Compact,

SFP Laser Driver

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC = +2.97V to +3.63V, TA = -40°C to +85°C. Typical values are at VCC = +3.3V, IBIAS = 20mA, IMOD = 30mA, TA= +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.

Power-Supply Voltage VCC ..................................-0.5V to +6.0V

Voltage at IN+, IN-, DIS…..…………………-0.5V to (VCC + 0.5V)

Voltage at BC_MON, MODSET, BIASSET .............-0.5V to +3.0V

Voltage at OUT+, OUT-.……………………+0.5V to (VCC + 1.5V)

Voltage at BIAS ............……………………+0.5V to (VCC + 0.5V)

Current into BIAS, OUT+, OUT- ......................-20mA to +150mA

Current into IN+, IN-......…………………………-20mA to +20mA

Continuous Power Dissipation (TA= +85°C)

16-Pin Thin QFN (derate 25mW/°C above +85°C) .............2W

Operating Junction Temperature Range ..........-55°C to +150°C

Storage Temperature Range .............................-55°C to +150°C

Die Attach Temperature ..................................................+400°C

Lead Temperature (soldering, 10s) .................................+300°C

Soldering Temperature (reflow)

Lead(Pb)-free...............................................................+260°C

Containing lead(Pb) .....................................................+240°C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Power-Supply Current ICC Excludes the laser bias and modulation

currents (Note 2) 22 35 mA

I/O SPECIFICATIONS

Differential Input Voltage VID V

ID = VIN+ - VIN-, Figure 1 0.2 2.4 VP-P

Common-Mode Input Voltage VINCM 0.6 

VCC V

Differential Input Resistance RIN 85 100 115 

DIS Input Pullup Resistance RPULL 4.7 7.2 10.0 k

VDIS = VCC 15

DIS Input Current VDIS = VGND, VCC = 3.3V, RPULL = 7.4k -450 μA

DIS Input High Voltage VIH 2.0 V

DIS Input Low Voltage VIL 0.8 V

BIAS GENERATOR

Bias Current Range IBIAS Current into BIAS pin 1 100 mA

Bias Off-Current IBIASOFF Current into BIAS pin, DIS asserted high 100 μA

5mA  IBIAS  10mA 70 85 95

BIASSET Current Gain GBIAS (Note 3) 10mA  IBIAS  100mA 79 85 91 A/A

BIASSET Current Gain Stability 10mA  IBIAS  100mA (Note 4) -4.4 +4 %

BIASSET Current Gain Linearity 10mA  IBIAS  100mA (Note 5) -2.3 +2.3 %

Bias Overshoot During SFP module hot plugging;

see Figure 3 (Notes 5, 6) 10 %

Bias-Current Monitor Gain (Note 5) 13.7 mA/A

1mA  IBIAS  5mA |4|

5mA  IBIAS  10mA -7 |2.8| +7

Bias-Current Monitor Gain

Stability (Notes 4, 5)

10mA  IBIAS  100mA -5 |2.4| +5

MAX3736

3.2Gbps, Low-Power, Compact,

SFP Laser Driver

_______________________________________________________________________________________ 3

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

Note 2: Maximum value is specified at IMOD = 60mA and IBIAS = 100mA. BC_MON connected to VCC.

Note 3: Modulation current gain, GMOD, is defined as GMOD = IMOD / IMODSET. Bias current gain, GBIAS, is defined as GBIAS =

IBIAS / IBIASSET. The nominal gain is measured at VCC = +3.3V and TA= +25°C.

Note 4: Gain stability is defined as [(Gain) - (Nom_Gain)] / (Nom_Gain) over the listed current range, temperature, and supply

variation. Nominal gain is measured at VCC = +3.3V, TA= +25°C. The voltage at the BC_MON pin must not exceed 1.39V.

Note 5: Guaranteed by design and characterization; see Figure 2.

Note 6: VCC turn-on time must be less than 0.8s, DC-coupled interface.

Note 7: The gain matching is defined as ABS [(GMOD/GBIAS - GMODNOM/GBIASNOM)/(GMODNOM/GBIASNOM)] over the specified

temperature and voltage supply range.

Note 8: For supply noise tolerance, noise is added to the supply (100mVP-P) up to 2MHz; see Figure 3.

ELECTRICAL CHARACTERISTICS (continued)

(VCC = +2.97V to +3.63V, TA = -40°C to +85°C. Typical values are at VCC = +3.3V, IBIAS = 20mA, IMOD = 30mA, TA= +25°C, unless

otherwise noted.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Current into OUT+, RL = 15,

VOUT+ and VOUT-  0.6V (DC-coupled) 5 60

Modulation Current Range IMOD Current into OUT+, RL = 15,

VOUT+ and VOUT-  2.0V (AC-coupled) 5 85

mAP-P

MODULATOR

5mA  IMOD  10mA 70 85 95

Modulation Current Gain GMOD (Note 3) 10mA  IMOD  85mA 79 85 91 A/A

Modulation Current Gain Stability 10mA  IMOD  85mA (Notes 4, 5) -4.4 +4 %

Modulation Current Gain Linearity 10mA  IMOD  85mA (Note 5) -3.3 +3.3 %

IBIASSET = 0.15mA; IMODSET = 0.7mA 2.3

IBIASSET = IMODSET = 0.15mA 0.1 1.4

IBIASSET = IMODSET = 0.4mA 0.1 1

IBIASSET = IMODSET = 0.6mA 0.1 1

Bias Current Gain and

Modulation Current Gain

Matching (Notes 5, 7)

IBIASSET = IMODSET = 0.9mA 0.1 1

Modulation OFF Current IMODOFF DIS asserted high 100 μA

Rise Time tR20% to 80%; 10mA  IMOD  60mA (Note 5) 48 80 ps

Fall Time tF80% to 20%; 10mA  IMOD  60mA (Note 5) 58 80 ps

10mA  IMOD  60mA; 2.67Gbps;

223-1 PRBS 16 38

10mA  IMOD  60mA; 3.2Gbps;

K28.5 pattern 17 38

10mA  IMOD  60mA; 155Mbps;

223-1 PRBS 30

psP-P

Deterministic Jitter

(Notes 5, 8)

10mA  IMOD  60mA; 3.2Gbps; K28.5;

TA = +100°C 6.3 ps

Random Jitter 10mA  IMOD  60mA (Note 5) 0.6 1 psRMS

OPTICAL EYE

(155Mbps)

MAX3736 toc01

919ps/div

117 MHz FILTER, 231 - 1 PRBS

1310nm FP LASER

OPTICAL EYE

(2.488Gbps)

MAX3736 toc02

58ps/div

ER = 8.2dB, OC-48 FILTER

231 - 1 PRBS, 1310 FP LASER

ELECTRICAL EYE

(2.488Gbps)

MAX3736 toc03

58ps/div

1870MHz FILTER

223 - 1 PRBS

Typical Operating Characteristics

(Typical values are at VCC = 3.3V, IBIAS = 20mA, IMOD = 30mA, TA= +25°C, unless otherwise noted.)

MAX3736

3.2Gbps, Low-Power, Compact,

SFP Laser Driver

4 _______________________________________________________________________________________

SOURCE

NOISE

VOLTAGE

SUPPLY 0.1μF 0.1μFOPTIONAL

OPTIONAL

TO LASER

DRIVER VCC

10μF

1μH

HOST BOARD

FILTER DEFINED BY SFP MSA

MODULE

Figure 3. Supply Filter

100mV MIN

1200mV MAX

CURRENT

VOLTAGE

VIN+

VIN-

(VIN+) - (VIN-)

IOUT+

200mVP-P MIN

2400mVP-P MAX

IMOD

Figure 1. Definition of Single-Ended Input Voltage Range

MAX3736

OSCILLOSCOPE

OUT-

OUT+

1.1pF

25Ω26Ω

130Ω

IOUT+

30Ω

VCC

50Ω

Figure 2. Output Termination for Characterization

MAX3736

3.2Gbps, Low-Power, Compact,

SFP Laser Driver

_______________________________________________________________________________________

SUPPLY CURRENT vs. TEMPERATURE

MAX3736 toc05

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

603510-15

-40 85

EXCLUDES IBIAS AND IMOD

BIAS CURRENT MONITOR GAIN

vs. TEMPERATURE

GAIN (mA/A)

MAX3736 toc06

TEMPERATURE (°C)

603510-15-40 85

MODULATION CURRENT

vs. MODSET RESISTANCE (ZL = 15Ω)

MAX3736 toc07

RMODSET (kΩ)

IMOD (mAP-P)

1 100

BIAS CURRENT vs. BIAS RESISTANCE

MAX3736 toc08

RBIASSET (kΩ)

IBIAS (mA)

100

1 100

EDGE TRANSITION TIME

vs. MODULATION AMPLITUDE

IMOD (mA)

EDGE TRANSITION TIME (ps)

5040302010 60

MAX3736 toc09

FALL TIME

RISE TIME

Typical Operating Characteristics (continued)

(Typical values are at VCC = 3.3V, IBIAS = 20mA, IMOD = 30mA, TA= +25°C, unless otherwise noted.)

MAX3736

3.2Gbps, Low-Power, Compact,

SFP Laser Driver

6 _______________________________________________________________________________________

Pin Description

PIN NAME FUNCTION

1, 4, 9,

12, 15 VCC +3.3V Supply Voltage. All pins must be connected to VCC.

2 IN+ Noninverted Data Input

3 IN- Inverted Data Input

5 BIASSET

A current DAC, a voltage DAC, or a resistor, connected from this pin to ground, sets the desired bias

current for the laser (see the Programming the Laser Bias Current section).

6 MODSET

A current DAC, a voltage DAC, or a resistor, connected from this pin to ground, sets the desired bias

current for the laser (see the Programming the Laser Modulation Current section).

7 BC_MON

Bias Current Monitor Output. Current out of this pin develops a ground-referenced voltage across an

external resistor that is proportional to the bias current.

8 BIAS Laser Bias Current Output

10 OUT+ Noninverted Modulation Current Output. IMOD flows into this pin when input data is high.

11 OUT- Inverted Modulation Current Output. IMOD flows into this pin when input data is low.

13, 14 GND Ground

16 DIS

Transmitter Disable, TTL. Laser output is disabled when DIS is asserted high or left

unconnected. The laser output is enabled when this pin is asserted low.

— EP

Exposed Pad. Must be soldered to the circuit board ground for proper thermal and electrical

performance (see the Exposed-Pad Package section).

Typical Operating Characteristics (continued)

(Typical values are at VCC = 3.3V, IBIAS = 20mA, IMOD = 30mA, TA= +25°C, unless otherwise noted.)

DETERMINISTIC JITTER

vs. MODULATION CURRENT

MAX3736 toc10

IMOD (mAP-P)

DJ (psP-P)

50403020

10 60

2.7Gbps

223-1 PRBS

DIFFERENTIAL S11 vs. FREQUENCY

MAX3736 toc11

FREQUENCY (GHz)

IS11I (dB)

8642

-25

-20

-15

-10

-5

-30

010

Detailed Description

The MAX3736 laser driver consists of three operational

blocks: a bias current generator, a modulation current

generator, and a high-speed modulation path. The

laser-biasing block includes a monitor output for bias-

sensing purposes. Both the bias and modulation gener-

ating blocks are enabled and disabled by the DIS pin.

The high-speed modulation path provides a 100Ω

differential input resistance.

Bias Current Generator

To maintain constant average optical power, the

MAX3736 is designed to interface to a laser controller

IC. The laser controller IC controls the MAX3736, and

maintains a constant laser power using an automatic

power-control (APC) circuit. A back-facet photodiode,

mounted in the laser package, is used to convert the

optical power into a photocurrent. The laser controller

IC adjusts the laser bias current so the monitor photodi-

ode’s current matches the level programmed by the

user. It does this by adjusting the current sourced by

the MAX3736’s BIASSET pin. The MAX3736 reacts by

increasing or decreasing the laser current at BIAS.

Bias Current Monitor

The MAX3736 features a bias current monitor

(BC_MON). This monitor is realized by mirroring a frac-

tion of the bias current and developing a voltage

across an external resistor connected to ground. For

example, connecting a 100Ωresistor to ground gives

the following relationship:

VBC_MON = (IBIAS / 73) x 100Ω. For compliance, the

voltage on BC_MON must be kept below 1.39V.

Modulation Current Generator

The laser’s modulation amplitude can be controlled by

placing a resistor from MODSET to ground. To set the

modulation amplitude, see the IMOD vs. RMODSET

graph in the

Typical Operating Characteristics

. A more

advanced control scheme employs the use of a laser

controller IC to control modulation current to

stabilize the extinction ratio. For more information on

controlling the extinction ratio, refer to Application

Note 1092:

HFAN-02.3.1: Maintaining Average Power

and Extinction Ratio, Part 1, Slope Efficiency and

Threshold Current

MAX3736

3.2Gbps, Low-Power, Compact,

SFP Laser Driver

_______________________________________________________________________________________ 7

IN+

1.2V 1.2V

x85

x1 x85

DIS

VCC VCC

VCC

16kΩ

82pF 7.2kΩ

24kΩ

50Ω50Ω

BIASSET MODSET

BIAS

BC_MON

IN-

OUT+

OUT-

MAX3736

Figure 4. Functional Diagram

MAX3736

High-Speed Modulation Driver

The output stage is composed of a high-speed differ-

ential pair and a programmable modulation current

source. The MAX3736 is optimized for driving a 15Ω

load; the minimum instantaneous voltage required at

OUT+ is 0.6V. Modulation current swings up to 60mA

are possible.

To interface with the laser diode, a damping resistor (RD)

is required for impedance matching. The combined

resistance of the series damping resistor and the equiva-

lent series resistance of the laser diode should equal

15Ω. To reduce optical output aberrations and duty-

cycle distortion caused by laser diode parasitic induc-

tance, an RC shunt network might be necessary. Refer to

Application Note 274:

HFAN-02.0: Interfacing Maxim

Laser Drivers with Laser Diodes

for more information.

At high data rates, e.g., 2.5Gbps, any capacitive load at

the cathode of a laser diode degrades optical output per-

formance. Because the BIAS output is directly connected

to the laser cathode, minimize the parasitic capacitance

associated with the pin by using an inductor to isolate the

BIAS pin parasitics from the laser cathode.

In the absence of input data, the modulation current

switches to OUT-, squelching the transceiver output.

Disable

The DIS pin disables the modulation and bias current.

The typical enable time is 2µs for bias current and 1µs

for modulation current. The typical disable time is 200ns

for bias current and 250µs for modulation current. The

DIS pin has a 7.4kΩinternal pullup resistor.

Design Procedure

Programming the Modulation Current

There are three methods for setting the modulation cur-

rent on the MAX3736 laser driver. The current can be

set by using a current DAC, a voltage DAC in series with

a resistor, or by using a resistor connected to GND.

To program the laser modulation current using a cur-

rent DAC, attach the DAC to the MODSET pin and set

the current using the following equation:

To program the laser modulation current using a volt-

age DAC, attach the DAC to the MODSET pin through a

series resistor, RSERIES, and set the current using the

following equation:

To program the laser modulation current using a resis-

tor, place the resistor from MODSET to ground. IMOD

current can be calculated by the following equation:

Programming the Bias Current

There are three methods for setting the bias current on

the MAX3736 laser driver. The current can be set by

using a current DAC, a voltage DAC in series with a

resistor, or by using a resistor connected to GND.

To program the laser bias current using a current DAC,

attach the DAC to the BIASSET pin and set the current

using the following equation:

To program the laser bias current using a voltage DAC,

attach the DAC to the BIASSET pin through a series

resistor, RSERIES, and set the current using the follow-

ing equation:

To program the laser bias current using a resistor,

place the resistor from BIASSET to ground. IBIAS cur-

rent can be calculated by the following equation:

BIAS BIASET

=×

12 85

IVV

BIAS DAC

SERIES

=−×

12 85

BIAS BIASET

=×85

MOD MODSET

=×

12 85

IVV

MOD DAC

SERIES

=−×

12 85

MOD MODSET

=×85

3.2Gbps, Low-Power, Compact,

SFP Laser Driver

8 _______________________________________________________________________________________

Input Termination Requirements

The MAX3736 data inputs are SFP MSA compliant. On-

chip 100Ω, differential input impedance is provided for

optimal termination (Figure 5). Because of the on-chip

biasing network, the MAX3736 inputs self-bias to the

proper operating point to accommodate AC-coupling.

Applications Information

Data Input Logic Levels

The MAX3736 is directly compatible with +3.3V reference

CML. Either DC or AC-coupling can be used for CML ref-

erenced to +3.3V. For all other logic types, AC-coupling

should be used. DC coupling to CML is fine, but it

negates the squelching function on the modulation path.

Modulation Currents Exceeding 60mA

For applications requiring a modulation current greater

than 60mA, headroom is insufficient for proper operation

of the laser driver if the laser is DC-coupled. To avoid

this problem, the MAX3736 modulation output can be

AC-coupled to the cathode of a laser diode. An external

pullup inductor is necessary to DC-bias the modulation

output at VCC. Such a configuration isolates laser for-

ward voltage from the output circuitry and allows the out-

put at OUT+ to swing above and below the supply

voltage (VCC). When AC-coupled, the MAX3736 modula-

tion current can be programmed from 5mA to 85mA.

Refer to Maxim Application Note

HFAN 02.0: Interfacing

Maxim’s Laser Drivers to Laser Diodes

for more informa-

tion on AC-coupling laser drivers to laser diodes.

Interface Models

Figures 5 and 6 show simplified input and output cir-

cuits for the MAX3736 laser driver.

Layout Considerations

To minimize loss and crosstalk, keep the connections

between the MAX3736 output and the laser as short as

possible. Use good high-frequency layout techniques

and multilayer boards with an uninterrupted ground

plane to minimize EMI and crosstalk.

Exposed-Pad Package

The exposed pad on the 16-pin QFN provides a very low

thermal resistance path for heat removal from the IC. The

pad is also electrical ground on the MAX3736 and must

be soldered to the circuit board ground for proper ther-

mal and electrical performance. Refer to Application

Note 862:

HFAN-08.1: Thermal Considerations of QFN

and Other Exposed-Paddle Packages

for additional

information.

MAX3736

3.2Gbps, Low-Power, Compact,

SFP Laser Driver

_______________________________________________________________________________________ 9

MAX3736

0.11pF

0.65nH

VCC

0.11pF

0.65nH

IN+

IN-

PACKAGE

50Ω

24kΩ

16kΩ82pF

Figure 5. Simplified Input Circuit Schematic

0.11pF

PACKAGE

OUT-

0.11pF

0.43nH

0.43nH OUT+

VCC

MAX3736

Figure 6. Simplified Output Circuit Schematic

MAX3736

Laser Safety and IEC 825

Using the MAX3736 laser driver alone does not ensure

that a transmitter design is compliant with IEC 825. The

entire transmitter circuit and component selections

must be considered. Customers must determine the

level of fault tolerance required by their application.

Please recognize that Maxim products are not

designed or authorized for use as components in sys-

tems intended for surgical implant into the body, for

applications intended to support or sustain life, or for

any other application where the failure of a Maxim

product could create a situation where personal injury

or death may occur.

Chip Information

PROCESS: SiGe BiPOLAR

Package Information

For the latest package outline information and land patterns,

go to www.maxim-ic.com/packages. Note that a “+”, “#”, or

“-” in the package code indicates RoHS status only. Package

drawings may show a different suffix character, but the drawing

pertains to the package regardless of RoHS status.

3.2Gbps, Low-Power, Compact,

SFP Laser Driver

10 ______________________________________________________________________________________

15 14 13

5678

DIS

VCC

GND

VCC

OUT-

OUT+

EP VCC

IN+

IN-

VCC

THE EXPOSED PAD MUST BE CONNECTED TO GROUND

FOR PROPER THERMAL AND ELECTRICAL PERFORMANCE.

BIASSET

MODSET

THIN QFN (3mm x 3mm)

BC_MON

BIAS

VCC

TOP VIEW

MAX3736

Pin Configuration

PACKAGE

TYPE

PACKAGE

CODE

OUTLINE

NO.

LAND

PATTERN NO.

16 TQFN-EP T1633-2 21-0136 90-0030

MAX3736

3.2Gbps, Low-Power, Compact,

SFP Laser Driver

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________

Revision History

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

0 12/03 Initial release —

1 2/06 Added lead(Pb)-free part to the Ordering Information table 1

2 9/10

Removed the dice package from the Ordering Information table and the Electrical

Characteristics table Note 1; removed the Wire-Bonding Die,Chip Topography/Pad

Configuration,Chip Topography, and Bonding Coordinates sections and Table 1; added

the soldering information for leaded and lead-free packages to the Absolute Maximum

Ratings section; added the Package Information table

1, 2, 3, 9,

10, 11