Datasheet

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

General Description

The MAX3656 is a burst-mode laser driver that oper-

ates at data rates from 155Mbps up to 2.5Gbps. The

laser driver accepts either positive-referenced emitter-

coupled logic (PECL) or current-mode logic (CML) data

inputs and provides bias and modulation current for the

laser diode. The device can switch the laser diode from

a completely dark (off) condition to a full (on) condition

(with proper bias and modulation currents) in less than

2ns. The MAX3656 incorporates DC-coupling between

laser driver and laser diode and operates with a single-

supply voltage as low as +3.0V.

A digital automatic power-control (APC) loop is provided

to maintain the average optical power over the full tem-

perature range and lifetime. The APC loop is functional

for a minimum burst on-time of 576ns and minimum

burst off-time of 96ns, with no limit on the maximum

burst on- or off-time. A fail monitor is provided to indi-

cate when the APC loop can no longer maintain the

average power. The MAX3656 can be configured for

nonburst-mode applications (continuous mode) by con-

necting burst enable (BEN) high. For power saving, the

MAX3656 provides enabling and disabling functionality.

The modulation current can be set from 10mA to 85mA

and the bias current can be set from 1mA to 70mA.

The MAX3656 is packaged in a small, 24-pin, 4mm

4mm thin QFN package and consumes only 132mW

(typ), excluding bias and modulation currents.

Applications

Fiber-to-the-Home (FTTH) and Fiber-to-the-

Business (FTTB) Broadband Access Systems

Passive Optical Network (PON) Transmitters

APON, EPON, and GPON Upstream Transmitters

Features

♦ Multirate Operation from 155Mbps to 2.5Gbps

♦ Burst Enable/Disable Delay <2ns

♦ Burst On-Time of 576ns to Infinity

♦ Infinite Bias-Current Hold Time Between Bursts

♦ DC-Coupled Operation with Single +3.3V Power

Supply

♦ 40mA Typical Supply Current

♦ Programmable Bias Current from 1mA to 70mA

♦ Programmable Modulation Current from 10mA

to 85mA

♦ Automatic Average Power Control with Failure

Monitor (No C

APC

Capacitor Needed)

♦ APC Loop Initialization ≤3 Bursts

MAX3656

155Mbps to 2.5Gbps Burst-Mode

Laser Driver

________________________________________________________________

Maxim Integrated Products

7 8 9 101112

192021222324

IN+

*EP

IN-

BEN+

BEN-

THIN QFN

GND

LONGB

BIAS-

BIAS+

OUT+

OUT-

GND

BIASMAX

MODSET

APCSET

TOP VIEW

*EXPOSED PAD IS CONNECTED TO GND

MAX3656

FAIL

Pin Configuration

MAX3656

GND

FAIL

LONGB

APCSET

MODSET

BIASMAX

+3.3V

IN-

IN+

SERIAL

DATA

SOURCE

130Ω130Ω

82Ω82Ω

+3.3V

BEN-

BEN+

BURST

CONTROL

130Ω130Ω

82Ω82Ω

OUT-

+3.3V

10nH

75Ω

+3.3V

10Ω

15Ω

OUT+

5.6Ω

BIAS+

5.6Ω

BIAS-

10Ω

27pF

Typical Application Circuit

19-2790; Rev 4; 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.

Ordering Information

PART TEMP RANGE PIN-PACKAGE

MAX3656ETG -40° C to +85°C 24 Thin QFN-EP*

MAX3656ETG+ -40° C to +85°C 24 Thin QFN-EP*

Functional Diagram appears at end of data sheet.

Summary of content (15 pages)

PAGE 1
9-2790; Rev 4; 9/10 155Mbps to 2.5Gbps Burst-Mode Laser Driver ♦ ♦ ♦ ♦ ♦ Multirate Operation from 155Mbps to 2.5Gbps Burst Enable/Disable Delay <2ns Burst On-Time of 576ns to Infinity Infinite Bias-Current Hold Time Between Bursts DC-Coupled Operation with Single +3.
PAGE 2
MAX3656 155Mbps to 2.5Gbps Burst-Mode Laser Driver ABSOLUTE MAXIMUM RATINGS Supply Voltage, VCC..............................................-0.5V to +6.0V Current into BIAS+, BIAS-, OUT+, OUT- ........-20mA to +150mA Current into MD.................................................... -5mA to +5mA Current into FAIL ...............................................-10mA to +10mA Voltage at IN+, IN-, BEN+, BEN-, EN, LONGB ...................................................-0.5V to (VCC + 0.
PAGE 3
155Mbps to 2.5Gbps Burst-Mode Laser Driver MAX3656 ELECTRICAL CHARACTERISTICS (continued) (Typical values are at VCC = +3.3V, IBIAS = 20mA, IMOD = 25mA, extinction ratio = 10dB, and TA = +25°C, unless otherwise noted.) PARAMETER Single-Ended Input Voltage SYMBOL CONDITIONS MIN VBEN+, VBEN- EN Input High Voltage VIH EN Input Low Voltage VIL TYP MAX 0.8 V 2.0 FAIL Output High Voltage VOH Sourcing 50μA, VCC = 3.0V FAIL Output Low Voltage VOL Sinking 100μA, VCC = 3.
PAGE 4
MAX3656 155Mbps to 2.5Gbps Burst-Mode Laser Driver ELECTRICAL CHARACTERISTICS (continued) (Typical values are at VCC = +3.3V, IBIAS = 20mA, IMOD = 25mA, extinction ratio = 10dB, and TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS BURST-MODE SPECIFICATIONS Burst Enable Delay APC closed loop (Notes 10, 11, 13) 2.3 ns Burst Disable Delay APC closed loop (Notes 10, 12, 13) 2.
PAGE 5
155Mbps to 2.5Gbps Burst-Mode Laser Driver MAX3656 VCC 22.1Ω BEN+ BEN ±MIDPOINT BEN- OUT- IFINAL × 110% 49.9Ω VCC IFINAL IBIAS + IMOD IFINAL × 90% MAX3656 10% OF IBIAS 22.1Ω IMOD ENABLE DELAY DISABLE DELAY OSCILLOSCOPE Z0 = 50Ω OUT+ VCC 50Ω 26.7Ω IBIAS Figure 1. Enable and Disable Delay Times Z0 = 50Ω BIAS+ 121Ω VCC 50Ω BIAS26.7Ω 35.7Ω Figure 2. Output Termination for Characterization Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) OPTICAL EYE DIAGRAM (155.
PAGE 6
Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) ELECTRICAL EYE DIAGRAM (2.5Gbps, IMOD = 30mA, PATTERN = PRBS 27 - 1 + 80 CID) SUPPLY CURRENT vs. TEMPERATURE (EXCLUDES IBIAS, IMOD, 15Ω LOAD) MAX3656 toc05 MAX3656 toc04 80 MAX3656 toc06 OPTICAL EYE DIAGRAM (2.48832Gbps, 2.
PAGE 7
155Mbps to 2.5Gbps Burst-Mode Laser Driver IMD vs. RAPCSET IBIASMAX vs. RBIASMAX IMOD vs. RMODSET 90 80 90 80 70 IMOD (mA) IMD (μA) 100 IBIASMAX (mA) 70 1000 60 50 40 60 50 40 30 30 20 20 10 10 0 0 10 0.
PAGE 8
MAX3656 155Mbps to 2.5Gbps Burst-Mode Laser Driver Pin Description PIN NAME 1, 4, 9, 15, 18, 21 VCC Power-Supply Voltage 2 IN+ Noninverting Data Input with On-Chip Biasing 3 IN- 5 BEN+ 6 BEN- 8 FUNCTION Inverting Data Input with On-Chip Biasing Noninverting Burst-Enable Input with On-Chip Biasing Inverting Burst-Enable Input with On-Chip Biasing TTL/CMOS Enable Input. Low for normal operation. Pull high or leave unconnected to disable laser bias and modulation currents.
PAGE 9
155Mbps to 2.5Gbps Burst-Mode Laser Driver The MAX3656 laser driver has three main parts: a highspeed modulator, a high-speed bias driver, and a laserbiasing block with automatic power control (see the Functional Diagram). Both the bias and modulation output stages are composed of differential pairs with programmable current sources. The circuit design is optimized for high-speed, low-voltage (3.3V), DC-coupled operation.
PAGE 10
MAX3656 155Mbps to 2.5Gbps Burst-Mode Laser Driver APC loop reset), and then it is driven low (chipenabled). In this case, APC loop initialization begins when the voltage at EN drops below the specified EN input low voltage of 0.8V. After initialization begins, the laser driver can be operating in burst mode (BEN toggling high and low) or continuous mode (BEN = high). In this case, the initialization time is 2.1µs (typ).
PAGE 11
155Mbps to 2.5Gbps Burst-Mode Laser Driver Setting the LONGB Input Pin Set the LONGB pin according to Table 2 to optimize APC loop operation. Interfacing with Laser Diodes The laser modulation current output OUT+ is optimized to drive a 15Ω load and must be DC-coupled. A series damping resistor, RD, provides impedance matching to the laser diode. The combined value of the series damping resistor and the laser diode equivalent series resistance should be close to 15Ω.
PAGE 12
MAX3656 155Mbps to 2.5Gbps Burst-Mode Laser Driver Design Example Select Laser Select a communication-grade laser for the proper data rate. Assume the laser output average power is PAVG = 0dBm, the operating temperature is -40°C to +85°C, and the laser diode has the following characteristics: wavelength: λ = 1.3µm, threshold current: ITH = 22mA at +25°C, threshold temperature coefficient: β TH = 1.3%/°C, laser-to-monitor transfer: ρ MON = 0.
PAGE 13
155Mbps to 2.5Gbps Burst-Mode Laser Driver LVTTL OR LVCMOS HIGH IN- R3 = 5kΩ BEN+ LVTTL OR LVCMOS LOW R4 = 3kΩ VCC BEN- from the burst-enable signal to BEN+. Connect a 5kΩ (R3) resistor from VCC to BEN+. Connect a 5kΩ resistor (R5) from VCC to BEN- and a 9kΩ resistor (R6) from BEN- to ground. For typical LVTTL or LVCMOS specifications of VCC to 2.0V for a high and 0.8V to 0V for a low, the LVTTL or LVCMOS sources a maximum of 75µA and sinks a maximum of 500µA.
PAGE 14
155Mbps to 2.5Gbps Burst-Mode Laser Driver MAX3656 Functional Diagram VCC RP LP OUT- MAX3656 IMOD OUT+ RD IN+ RCOMP CCOMP IN- IBIAS BEN+ BIAS+ BEN- RD VCC BIAS- APC DAC RMODSET RBIASMAX DSP EN FAIL Chip Information TRANSISTOR COUNT: 8153 PROCESS: SiGe BIPOLAR 14 ASP LONGB MD RAPCSET 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.
PAGE 15
5Mbps to 2.