Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - laser controller Laser diode driver (LWL) TQFN 20 Surface-mount

General Description

The MAX3996 is a high-speed laser driver for small-

form-factor (SFF) fiber optic LAN transmitters. It con-

tains a bias generator, a laser modulator, and

comprehensive safety features. Automatic power con-

trol (APC) adjusts the laser bias current to maintain

average optical power, regardless of changes in tem-

perature or laser properties. The driver accommodates

common anode or differential laser configurations. The

output current range of the MAX3996 is appropriate for

VCSELs and high-efficiency edge-emitting lasers.

The MAX3996 operates up to 3.2Gbps. It can switch up

to 30mA of laser modulation current and sink up to

60mA bias current. Adjustable temperature compensa-

tion is provided to keep the optical extinction ratio with-

in specifications over the operating temperature range.

The MAX3996 accommodates various laser packages,

including low-cost TO-46 headers. Low deterministic jit-

ter (9ps

P-P

), combined with fast edge transitions,

(65ps) provides excellent margins compared to indus-

try-standard transmitter eye masks.

This laser driver provides extensive safety features to

guarantee single-point fault tolerance. Safety features

include a transmit disable, redundant shutdown, and

laser-bias monitoring. The safety circuit detects faults

that could cause hazardous light levels and immediate-

ly disables the laser output. The MAX3996 safety cir-

cuits are compliant with SFF and small-form-factor

pluggable (SFP) multisource agreements (MSA).

The MAX3996 is available in a compact 4mm ✕ 4mm,

20-pin QFN package and a 20-pin thin QFN package. It

operates over a temperature range of 0°C to +70°C.

Applications

Fibre Channel Optical Transmitters

VCSEL Transmitters

Gigabit Ethernet Optical Transmitters

ATM LAN Optical Transmitters

10 Gigabit Ethernet WWDM

Features

♦ 9ps

P-P

Deterministic Jitter

♦ 20-Pin QFN 4mm

✕ 4mm Package

♦ 3.0V to 5.5V Supply Voltage

♦ Automatic Power Control

♦ Integrated Safety Circuits

♦ 30mA Laser Modulation Current

♦ Temperature Compensation of Modulation

Current

♦ Compliant with SFF and SFP MSA

MAX3996

3.0V to 5.5V, 2.5Gbps VCSEL

and Laser Driver

________________________________________________________________ Maxim Integrated Products 1

MAX3996

0.01µF

PORDLY

MOD

COMP

N.C.

0.01µF

L1*

25Ω

OPTIONAL SHUTDOWN

CIRCUITRY

1.8kΩ

TX_DISABLE

FAULT

IN+

IN-

PORDLY

TC MODSET MON1 MON2 COMP GND

BIAS

OUT+

OUT-

SHDNDRV

*FERRITE BEAD

SET

Typical Application Circuit

Ordering Information

19-2194; Rev 3; 5/04

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.

PART

TEMP

RANGE

PIN-

PACKAGE

CODE

MAX3996CGP

0°C to +70°C

20 QFN G2044-3

MAX3996CTP+

0°C to +70°C 20 Thin QFN

T2044-3

Pin Configuration appears at end of data sheet.

Denotes Lead-Free Package

Summary of content (16 pages)

PAGE 1
9-2194; Rev 3; 5/04 3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver The MAX3996 is a high-speed laser driver for smallform-factor (SFF) fiber optic LAN transmitters. It contains a bias generator, a laser modulator, and comprehensive safety features. Automatic power control (APC) adjusts the laser bias current to maintain average optical power, regardless of changes in temperature or laser properties. The driver accommodates common anode or differential laser configurations.
PAGE 2
MAX3996 3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver ABSOLUTE MAXIMUM RATINGS Supply Voltage at VCC...........................................-0.5V to +7.0V Voltage at TX_DISABLE, PORDLY, MON1, COMP, IN+, IN-, MD, BIAS, MODSET, TC..........-0.5V to (VCC + 0.5V) Voltage between COMP and MON2 .....................................2.3V Voltage between IN+ and IN- ..................................................5V Voltage at OUT+, OUT- .........................
PAGE 3
.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver (VCC = 3.0V to 5.5V, TA = 0°C to +70°C, unless otherwise noted. Typical values are at VCC = 3.3V, TC pin not connected, TA = +25°C.) (Figure 1) PARAMETER SYMBOL Minimum Modulation Current iMOD Maximum Modulation Current iMOD Accuracy of Modulation Current (Part-to-Part Variation) Edge Transition Time tr, tf Deterministic Jitter Random Jitter CONDITIONS MIN TYP RL ≤ 25Ω 30 40 RMODSET = 2.
PAGE 4
Typical Operating Characteristics (VCC = 3.3V, TA = +25°C, unless otherwise noted.) 25Ω LOAD 120mV/ div MAX3996 toc03 MAX3996 toc02 25Ω LOAD OPTICAL EYE DIAGRAM (iMOD = 5mA, 850nm VCSEL, 27 - 1 PRBS, 2.5Gbps, 1870MHz FILTER) ELECTRICAL EYE DIAGRAM (iMOD = 30mA, 27 - 1 PRBS, 3.2Gbps) MAX3996 toc01 ELECTRICAL EYE DIAGRAM (iMOD = 30mA, 27 - 1 PRBS, 2.5Gbps) 120mV/ div 64ps/div 57ps/div 52ps/div OPTICAL EYE DIAGRAM (iMOD = 15mA, 1310nm LASER, 27 - 1 PRBS, 2.
PAGE 5
3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver STARTUP WITH SLOW RAMPING SUPPLY LOW FAULT MAX3996 toc11 0V VCC 3.3V LOW FAULT LOW TX_DISABLE LOW HIGH t_init = 23mS LOW TX_DISABLE TX_DISABLE LASER OUPUT LASER OUPUT RESPONSE TO FAULT t_off = 60ns LOW FAULT RECOVERY TIME EXTERNALLY FORCED FAULT ON FAULT 20.0µs/div MAX3996 toc13 TRANSMITTER DISABLE MAX3996 toc12 10.0ms/div VMON2 LOW LASER OUPUT 10.0ms/div 3.3V VCC t_on = 37µs t_fault = 14µs MAX3996 toc14 FAULT 3.
PAGE 6
3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver MAX3996 Pin Description PIN NAME 1 TC FUNCTION Temperature Compensation Set. The resistor at TC programs the temperature-increasing component of the laser-modulation current. 2 FAULT 3, 9 GND 4 TX_DISABLE 5 PORDLY 6, 16, 19 VCC 7 IN+ Noninverting Data Input 8 IN- Inverting Data Input 10 MON1 11 MON2 This pin attaches to the emitter of the bias driving transistor. See the Design Procedure section.
PAGE 7
3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver MAX3996 3.0V TO 5.5V VOLTS VIN+ ICC VCC iOUT ROUT 100mVP-P MIN 1100mVP-P MAX VIN- VCC MAX3996 SINGLE-ENDED SIGNAL DIFFERENTIAL SIGNAL FERRITE BEAD* ROUT 200mVP-P MIN 2200mVP-P MAX VID = VIN+ - VINOUTOUT+ 0.01µF IN+ 0.01µF VID CURRENT iMOD iMOD 0.01µF RIN 0.01µF IN- 25Ω 25Ω MODULATION CURRENT GENERATOR TC TIME Figure 2. Required Input Signal and Modulation-Current Polarity MODSET Bias Generator RMOD *MURATA BLM11HA102SG Figure 1.
PAGE 8
Table 1. Typical Fault Conditions PIN VCC FAULT CONDITION MON2 VMON2 > 400mV BIAS VBIAS < 400mV TC, MODSET VMODSET or VTC < 200mV 50Ω OUT+ 100Ω IN- ENABLE Many of the modulator performance specifications depend on total modulator current. To ensure good driver performance, the voltage at either OUT+ or OUT- must not be less than VCC - 1V. The amplitude of the modulation current is set with resistors at the MODSET and temperature coefficient (TC) pins.
PAGE 9
3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver MAX3996 Table 2. RTC and RMOD Selection Table iMOD = 30mA iMOD = 15mA iMOD = 5mA TEMPCO (ppm/°C) RMOD (kΩ) RTC (kΩ) RMOD (kΩ) RTC (kΩ) 3500 17.1 1.85 34.4 3.94 104 12.3 3000 8.04 2.19 16.3 4.64 49.5 14.4 2500 5.20 2.68 10.6 5.62 32.4 17.4 2000 3.81 3.42 7.86 7.08 24.1 21.8 1500 2.98 4.64 6.21 9.53 19.1 29.1 1000 2.44 7.08 5.12 14.4 15.9 43.8 500 2.05 14.4 4.34 29.1 13.5 87.8 RMOD (kΩ) RTC (kΩ) Table 3.
PAGE 10
MAX3996 3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver Programming Modulation Current VCC PORDLY STARTUP DELAY VBG SHDNDRV BIAS ENABLE TX_DISABLE MODULATOR ENABLE FAULT LATCH FAULT R Q BIAS FAULT 1 BIAS FAULT 2 TC FAULT MODSET FAULT S Resistors at the MODSET and TC pins set the amplitude of the modulation current. The resistor RMOD sets the temperature-stable portion of the modulation current, and the resistor (R TC) sets the temperatureincreasing portion of the modulation current.
PAGE 11
3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver 1000 500ppm 1000ppm 2000ppm 1500ppm RTC (kΩ) 2500ppm 3000ppm 3500ppm Designing the Bias Filter and Output Pullup Beads 10 5mA To reduce deterministic jitter, add a ferrite bead inductor (L1) between the BIAS pin and the cathode of the laser. Select L1 to have an impedance >100Ω between f = 10MHz and f = 2GHz, and a DC resistance < 3Ω; Maxim recommends the Murata BLM11HA102SG.
PAGE 12
MAX3996 3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver VCC OPTIONAL SHUTDOWN CIRCUITRY SHDNDRV VCC MAX3996 SMOOTH START MONITOR DIODE LASER SHUTDOWN CIRCUIT L1* 1.1V BIAS IBIAS MD MON2 POWER-CONTROL AMPLIFIER RSET ID *FERRITE BEAD 11Ω BIAS DISABLE CCOMP 0.1µF MON1 COMP Figure 11. APC Loop monitor photodiode current is set by ID = VMD/RSET. Determine the desired monitor current (ID), and then select RSET = 1.1V/ID.
PAGE 13
3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver UNCOMPENSATED POWER CORRECTLY COMPENSATED product could create a situation where personal injury or death may occur. Layout Considerations The MAX3996 is a high-frequency product whose performance largely depends upon the circuit board layout. Use a multilayer circuit board with a dedicated ground plane. Use short laser-package leads placed close to the modulator outputs.
PAGE 14
MAX3996 3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver VCC MAX3996 10kΩ 550Ω 60Ω SHDNDRV Figure 14. SHDNDRV Output VCC VCC PACKAGE PACKAGE 50Ω 1.1nH 50Ω OUT- OUT+ 0.15pF 1.1nH 0.15pF 1pF 1pF MAX3996 Figure 15.
PAGE 15
3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver MAX3996 VCC VCC MAX3996 PACKAGE MAX3996 BIAS VCC 1.1nH IN+ VCC 0.15pF 1pF MON2 100Ω VCC 1.1nH VCC 11Ω INMON1 0.15pF 1pF Figure 16. Data Inputs Figure 17.
PAGE 16
3.0V to 5.5V, 2.5Gbps VCSEL and Laser Driver MAX3996 Package Information For the latest package outline information, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE MAX3996CGP 20 QFN 4mm x 4mm x 0.9mm G2044-3 MAX3996CTP+ 20 Thin QFN 4mm x 4mm x 0.8mm T2044-3 PART Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.