Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - laser controller Laser diode driver (LWL) TQFN 24 Surface-mount

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

Ordering Information

19-3161; Rev 2; 6/11

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.

EVALUATION KIT

AVAILABLE

BIAS

APCFILT2

TX_DISABLE

MODTCOMP

TH_TEMP

OUT+

APCFILT1

SHUTDOWN

GND

BC_MON

TX_FAULT

GND

MODSET

APCSET

7 8 9 10 11 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

*EP

Pin Configuration

Typical Application Circuit appears at end of data sheet.

Denotes a lead-free/RoHS-compliant package.

EP = Exposed pad.

T = Tape and reel.

PART TEMP RANGE PIN-PACKAGE

MAX3646ETG -40°C to +85°C 24 Thin QFN-EP*

MAX3646ETG-T -40°C to +85°C 24 Thin QFN-EP*

MAX3646ETG+ -40°C to +85°C 24 Thin QFN-EP*

MAX3646ETG+T -40°C to +85°C 24 Thin QFN-EP*

Summary of content (15 pages)

PAGE 1
9-3161; Rev 2; 6/11 KIT ATION EVALU E L B AVAILA 155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control Features The MAX3646 is a +3.3V laser driver designed for multirate 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 compensation, and built-in thermal compensation.
PAGE 2
MAX3646 155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control ABSOLUTE MAXIMUM RATINGS Supply Voltage VCC...............................................-0.5V to +6.0V IN+, IN-, TX_DISABLE, TX_FAULT, SHUTDOWN, BC_MON, PC_MON, APCFILT1, APCFILT2, MD, TH_TEMP, MODTCOMP, MODBCOMP, MODSET, and APCSET Voltage.............-0.5V to (VCC + 0.5V) OUT+, OUT-, BIAS Current.............................-20mA to +150mA Continuous Power Dissipation (TA = +70°C) 24-Pin TQFN (derate 27.8mW/°C above +70°C) ..
PAGE 3
155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control (VCC = +2.97V to +3.63V, TA = -40°C to +85°C. Typical values are at VCC = +3.3V, IBIAS = 60mA, IMOD = 60mA, TA = +25°C, unless otherwise noted.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 1500 µA 1.4 V 1.
PAGE 4
Typical Operating Characteristics (VCC = +3.3V, CAPC = 0.01µF, IBIAS = 20mA, IMOD = 30mA, TA = +25°C, unless otherwise noted.) OPTICAL EYE DIAGRAM (622.08Mbps, 27 - 1 PRBS, 467MHz FILTER) ELECTRICAL EYE DIAGRAM (IMOD = 30mA, 622.08MHz, 27 - 1 PRBS) OPTICAL EYE DIAGRAM (155Mbps, 27 - 1 PRBS, 117MHz FILTER) MAX3646 toc01 MAX3646 toc03 MAX3646 toc02 1310nm FP LASER re = 8.2dB 2pF BETWEEN OUT+ AND OUT- 1310nm FP LASER re = 8.2dB 75mV/div 270ps/div 1ns/div 320ps/div SUPPLY CURRENT (ICC) vs.
PAGE 5
155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control 1.8 1.6 1.4 100 MAX3646 toc11 10 MAX3646 toc10 2.0 90 1.0 0.8 IMOD (mA) 1.2 RTH_TEMP = 7kΩ 70 60 0.1 0.6 RTH_TEMP = 12kΩ 80 1 K (mA/mA) RJ (psRMS) TEMPERATURE COMPENSATION vs. RTH_TEMP (RMODTCOMP = 500Ω) COMPENSATION (K) vs. RMODBCOMP MAX3646 toc12 RANDOM JITTER vs. MODULATION CURRENT 50 RTH_TEMP = 4kΩ RTH_TEMP = 2kΩ 0.4 40 0.2 0 0 10 20 30 40 50 60 70 80 90 IMOD (mA) 0.
PAGE 6
155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control MAX3646 Pin Description PIN 1 6 NAME FUNCTION Modulation-Current Compensation from Temperature. A resistor at this pin sets the temperature MODTCOMP coefficient of the modulation current when above the threshold temperature. Leave open for zero temperature compensation. 2, 5, 14, 17 VCC +3.3V Supply Voltage 3 IN+ Noninverted Data Input 4 IN- Inverted Data Input 6 TX_DISABLE 7 PC_MON Photodiode-Current Monitor Output.
PAGE 7
155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control MAX3646 VOLTAGE SINGLE ENDED VIN+ 100mV (min) VIN- 1200mV (max) DIFFERENTIAL (VIN+) - (VIN-) 1μF 21Ω 200mV (min) MAX3646 OSCILLOSCOPE OUT- 2400mV (max) BIAS-T CURRENT OUT+ IOUT+ 21Ω IMOD BIAS-T 50Ω 50Ω 1μF TIME Figure 1. Required Input Signal and Output Polarity Figure 2. Test Circuit for Characterization HOST BOARD FILTER DEFINED BY SFP MSA L1 1μH SOURCE NOISE VOLTAGE SUPPLY MODULE C1 0.
PAGE 8
MAX3646 155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control VCC SHUTDOWN MAX3646 INPUT BUFFER IN+ DATA PATH IN- OUTOUT+ IMOD ENABLE SHUTDOWN SAFETY LOGIC AND POWER DETECTOR TX_FAULT TX_DISABLE RD IMOD IBIAS ENABLE BIAS VCC IBIAS RPULL = 45kΩ VCC IMD 1 VBG IBIAS APCSET RAPCSET PC_MON x1/2 RPC_MON xTC x268 xK IAPCSET IBIAS 82 MD T > TTH BC_MON IMD CMD RBC_MON T x1 VBG TH_TEMP RTH_TEMP MODTCOMP RMODTCOMP MODSET MODBCOMP RMODSET APCFILT1 APCFILT2 RMODBCOM
PAGE 9
155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control MAX3646 VCC POR AND COUNTER 60ms DELAY IMOD ENABLE TX_DISABLE COUNTER 60ms DELAY 100ns DELAY IBIAS ENABLE VCC IMD 1 VREF PC_MON Q R COMP VCC RPC_MON IBIAS 82 RS LATCH VREF BC_MON S SHUTDOWN COMP RBC_MON CMOS EXCESSIVE APC CURRENT SETPOINT EXCESSIVE MOD CURRENT SETPOINT TX_FAULT TTL OPEN COLLECTOR Figure 5. Simplified Safety Circuit Table 1.
PAGE 10
MAX3646 155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control Table 2. Circuit Responses to Various Single-Point Faults PIN TX_FAULT TX_DISABLE CIRCUIT RESPONSE TO OVERVOLTATGE OR SHORT TO VCC Does not affect laser power. CIRCUIT RESPONSE TO UNDERVOLTAGE OR SHORT TO GROUND Does not affect laser power. Modulation and bias currents are disabled. Normal condition for circuit operation. IN+ The optical average power increases and a fault occurs if VPC_MON exceeds the threshold.
PAGE 11
155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control PARAMETER Average power SYMBOL RELATION PAVG PAVG = (P0 + P1) / 2 Extinction ratio re r e = P1 / P 0 Optical power of a one P1 P1 = 2PAVG x re / (re + 1) Optical power of a zero P0 P0 = 2PAVG / (re + 1) PP-P PP-P = P1 - P0 Optical amplitude η η = PP-P / IMOD Modulation current IMOD IMOD = PP-P / η Threshold current ITH P0 at I ≥ ITH IBIAS IBIAS ≥ ITH + IMOD / 2 Laser slope efficiency Bias current (AC-coupled)
PAGE 12
MAX3646 155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control of RMODSET that corresponds to the required current at +25°C: IMOD = IMODS + K x IBIAS + IMODT IMODS = 268 x VREF / RMODSET IMODT = TC x (T - TTH) | T > TTH IMODT = 0 | T < TTH An external resistor at the MODBCOMP pin sets current proportional to IBIAS.
PAGE 13
155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control Determine CAPC The APC loop filter capacitor (CAPC) must be selected to balance the requirements for fast turn-on and minimal interaction with low frequencies in the data pattern. The low-frequency cutoff is: CAPC(µF) ≅ 68 / (f3dB(kHz) x (η x ρMON)1.
PAGE 14
155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control MAX3646 Typical Application Circuit +3.3V OPTIONAL SHUTDOWN CIRCUITRY IN+ CDR VCC SHUTDOWN 0.1μF TX_FAULT TX_DISABLE +3.3V 0.01μF +3.3V 15Ω OUT- 0.1μF 10Ω IN- OUT+ RMODBCOMP MAX3646 MODBCOMP BIAS RMODTCOMP FERRITE BEAD MODTCOMP MD RTH_TEMP CMD PC_MON BC_MON RBC_MON CAPC RPC_MON APCFILT2 APCFILT1 APCSET RAPCSET RMODSET GND MODSET TH_TEMP REPRESENTS A CONTROLLED-IMPEDANCE TRANSMISSION LINE.
PAGE 15
5Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control REVISION NUMBER REVISION DATE 0 1/04 1 2 DESCRIPTION PAGES CHANGED Initial release — 7/04 Added the lead(Pb)-free package option to the Ordering Information 1 6/11 Updated Ordering Information; changed Absolute Maximum Ratings to reflect lead and soldering specs; changed continuous power dissipation specs; updated biascurrent monitor ratio in Electrical Characteristics table; changed the APCSET and MODSET function descriptio