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General Description

The MAX3646 is a +3.3V laser driver designed for mul-

tirate transceiver modules with data rates from

155Mbps to 622Mbps. Lasers can be DC-coupled to

the MAX3646 for reduced component count and ease

of multirate operation.

Laser extinction ratio control (ERC) combines the features

of automatic power control (APC), modulation compensa-

tion, and built-in thermal compensation. The APC loop

maintains constant average optical power. Modulation

compensation increases the modulation current in pro-

portion to the bias current. These control loops, com-

bined with thermal compensation, maintain a constant

optical extinction ratio over temperature and lifetime.

The MAX3646 accepts differential data input signals.

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

ulation current range and up to 100mA bias current

range, make the MAX3646 ideal for driving FP/DFB

lasers in fiber optic modules. External resistors set the

required laser current levels. The MAX3646 provides

transmit disable control (TX_DISABLE), single-point

fault tolerance, bias-current monitoring, and photocur-

rent monitoring. The device also offers a latched failure

output (TX_FAULT) to indicate faults, such as when the

APC loop is no longer able to maintain the average

optical power at the required level. The MAX3646 is

compliant with the SFF-8472 transmitter diagnostic and

SFP MSA timing requirements.

The MAX3646 is offered in a 4mm x 4mm, 24-pin thin

QFN package and operates over the extended -40°C to

+85°C temperature range.

Applications

Multirate OC-3 to OC-12 FEC Transceivers

125Mbps Ethernet SFP, GBIC, and 1 x 9

Transceivers

Features

♦ Single +3.3V Power Supply

♦ 47mA Power-Supply Current

♦ 85mA Modulation Current

♦ 100mA Bias Current

♦ Automatic Power Control (APC)

♦ Modulation Compensation

♦ On-Chip Temperature Compensation

♦ Self-Biased Inputs for AC-Coupling

♦ Ground-Referenced Current Monitors

♦ Laser Shutdown and Alarm Outputs

♦ Enable Control and Laser Safety Feature

MAX3646

155Mbps to 622Mbps SFF/SFP

Laser Driver with Extinction Ratio Control

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-3161; Rev 0; 1/04

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.

EVALUATION KIT

AVAILABLE

PART

TEMP

RANGE

PIN-

PACKAGE

PKG

CODE

MAX3646ETG

-40°C to +85°C 24 Thin QFN

T2444-1

BIAS

APCFILT2

TX_DISABLE

MODTCOMP

TH_TEMP

OUT+

APCFILT1

SHUTDOWN

GND

BC_MON

TX_FAULT

GND

MODSET

APCSET

7891011 12

24 23 22 21 20 19

TOP VIEW

THE EXPOSED PADDLE MUST BE SOLDERED TO SUPPLY

GROUND ON THE CIRCUIT BOARD.

IN+

IN-

PC_MON

OUT-

MODBCOMP

MAX3646

Pin Configuration

Typical Application Circuit appears at end of data sheet.

1 2 3 4 5 6 ... 13 14

155Mbps to 622Mbps SFF/SFP 1

Sommario

Pagina 1 - 155Mbps to 622Mbps SFF/SFP

General DescriptionThe MAX3646 is a +3.3V laser driver designed for mul-tirate transceiver modules with data rates from155Mbps to 622Mbps. Lasers can

Pagina 2

MAX3646Safety CircuitryThe safety circuitry contains a disable input (TX_DISABLE), a latched fault output (TX_FAULT), andfault detectors (Figure 5). T

Pagina 3

Design ProcedureWhen designing a laser transmitter, the optical output isusually expressed in terms of average power andextinction ratio. Table 3 show

Pagina 4

MAX3646Current Compliance (IMOD≤ 60mA), DC-CoupledThe minimum voltage at the OUT+ and OUT- pins is0.7V.For:VDIODE= Diode bias point voltage (1.2V typ)

Pagina 5

Layout ConsiderationsTo minimize loss and crosstalk, keep the connectionsbetween the MAX3646 output and the laser diode asshort as possible. Use good

Pagina 6

MAX3646155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio ControlMaxim cannot assume responsibility for use of any circuitry other than cir

Pagina 7

MAX3646155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control2 ________________________________________________________________________

Pagina 8

MAX3646155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control__________________________________________________________________________

Pagina 9

MAX3646155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control4 ________________________________________________________________________

Pagina 10

MAX3646155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control__________________________________________________________________________

Pagina 11

MAX3646155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control6 ________________________________________________________________________

Pagina 12

Detailed DescriptionThe MAX3646 laser driver consists of three main parts:a high-speed modulation driver, biasing block withERC, and safety circuitry.

Pagina 13

MAX3646Average power is regulated using APC, which keepsconstant current from a photodiode coupled to thelaser. Peak-to-peak power is maintained by co

Pagina 14

MAX3646155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control__________________________________________________________________________

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