Datasheet

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Typical Application Circuit

General Description

The MAX3942 is designed to drive high-speed optical

modulators at data rates up to 10.7Gbps. It functions as

a modulation circuit, with an integrated control op amp

externally programmed by a DC voltage.

A high-bandwidth, fully differential signal path is inter-

nally implemented to minimize jitter accumulation. When

a clock signal is available, the integrated data-retiming

function can be selected to reject input-signal jitter.

The MAX3942 receives differential CML signals (ground-

referenced) with on-chip line terminations of 50Ω. Each

of the differential outputs has an on-chip 50Ω resistor for

back termination. The driver is able to deliver a modula-

tion current of 40mA

P-P

to 120mA

P-P

, with an edge

speed of 23ps (typical 20% to 80%). This modulation

current reflects a modulation voltage of 1.0V

P-P

to 3.0V

P-

single ended or 2.0V

P-P

to 6.0V

P-P

differential.

The MAX3942 also includes an adjustable pulse-width

control circuit to precompensate for asymmetrical mod-

ulator characteristics. It is available in a compact 4mm

✕ 4mm, 24-pin thin QFN package and operates over

the -40°C to +85°C temperature range.

Features

♦ 23ps Edge Speed

♦ Single-Ended Modulation Voltage Up to 3V

P-P

♦ Differential Modulation Voltage Up to 6V

P-P

♦ Selectable Data-Retiming Latch

♦ Up to 10.7Gbps Operation

♦ 50Ω On-Chip Input and Output Terminations

♦ Pulse-Width Adjustment

♦ Enable and Polarity Controls

♦ ESD Protection

Applications

Mach Zehnder Modulators

Packaged Direct-Modulated Lasers

SONET OC-192 and SDH STM-64 Transmission

Systems

DWDM Systems

Long/Short-Reach Optical Transmitters

10Gbps Ethernet

MAX3942

10Gbps Modulator Driver

________________________________________________________________

Maxim Integrated Products

MAX3952

0.01μF

DATA+ DATA+

PLRT GND

50Ω

0.01μF

DATA- DATA-

50Ω

0.01μF

CLK+ CLK+

OUT+

50Ω

0.01μF

CLK- CLK-

REPRESENTS A CONTROLLED-IMPEDANCE TRANSMISSION LINE.

-5.2V

50Ω

10Gbps

SERIALIZER

2kΩ

PWC+ PWC- V

MODSET

1000pF

-5.2V

0.1μF

-5.2V

MODEN

RTEN

50Ω

OUT-

50Ω

MAX3942

50Ω

0.01μF

MACH ZEHNDER

MODULATOR

L1 AND L2 ARE HIGH-FREQUENCY FERRITE BEADS

19-2934; Rev 1; 6/07

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.

Ordering Information

PART TEMP RANGE PIN-PACKAGE

MAX3942ETG -40°C to +85°C 24 Thin QFN (4mm

 4mm)

MAX3942ETG+ -40°C to +85°C 24 Thin QFN (4mm  4mm)

Pin Configuration appears at end of data sheet.

Denotes a lead-free package.

Summary of content (10 pages)

PAGE 1
9-2934; Rev 1; 6/07 10Gbps Modulator Driver Features ♦ 23ps Edge Speed The MAX3942 is designed to drive high-speed optical modulators at data rates up to 10.7Gbps. It functions as a modulation circuit, with an integrated control op amp externally programmed by a DC voltage. A high-bandwidth, fully differential signal path is internally implemented to minimize jitter accumulation. When a clock signal is available, the integrated data-retiming function can be selected to reject input-signal jitter.
PAGE 2
MAX3942 10Gbps Modulator Driver ABSOLUTE MAXIMUM RATINGS Continuous Power Dissipation (TA = +85°C) 24-Pin Thin QFN (derate 20.8mW/° above +85°C) ....1354mW Current into or out of OUT+, OUT-.................……………...80mA Storage Temperature Range .....................……-55°C to +150°C Operating Temperature Range ....................……-40°C to +85°C Lead Temperature (soldering, 10s)............………………+300°C Supply Voltage VEE ..............................................-6.0V to +0.
PAGE 3
10Gbps Modulator Driver (VEE = -5.5V to -4.9V, TA = -40°C to +85°C. Typical values are at VEE = -5.2V, IMOD = 100mA, and TA = +25°C, unless otherwise noted.
PAGE 4
10Gbps Modulator Driver MAX3942 Test Circuits and Timing Diagrams 0V 100mV 1.0V -0.5V -1.0V (a) DC-COUPLED SINGLE-ENDED CML INPUT 0.4V 800mV 0V -0.4V 100mV (b) AC-COUPLED SINGLE-ENDED (CML OR PECL) INPUT Figure 1. Definition of Single-Ended Input Voltage Range CLK+ VIS = 0.1VP-P TO 1VP-P DC-COUPLED 0.1VP-P TO 0.8VP-P AC-COUPLED CLKtSU tHD DATA- DATA+ (DATA+) - (DATA-) VID = 0.2VP-P TO 2VP-P DC-COUPLED 0.2VP-P TO 1.
PAGE 5
10Gbps Modulator Driver PLRT 50Ω RTEN MODEN PWC+ PWC- CLK+ IOUT- 50Ω OSCILLOSCOPE CLK- PATTERN GENERATOR MAX3942 50Ω DATA+ 50Ω DATA- OUT- 50Ω OUT+ 50Ω 50Ω IOUT+ ZL VEE MODSET -5.2V GND VMODSET 0.1μF 1000pF VEE Figure 3.
PAGE 6
Typical Operating Characteristics (Typical values are at VEE = -5.2V, IMOD = 100mA, TA = +25°C, unless otherwise noted.) SUPPLY CURRENT vs. TEMPERATURE (50Ω LOAD, EXCLUDES IMOD) 10.7Gbps ELECTRICAL EYE DIAGRAM (VMOD = 6VP-P DIFFERENTIAL, 231 - 1 PRBS) MAX3942 toc03 170 MAX3942 toc02 MAX3942 toc01 10.
PAGE 7
10Gbps Modulator Driver PIN NAME 1 DATA+ Noninverting Data Input, with 50Ω On-Chip Termination FUNCTION 2 DATA- Inverting Data Input, with 50Ω On-Chip Termination 3, 4, 14, 17 GND Ground. All pins must be connected to board ground.
PAGE 8
MAX3942 10Gbps Modulator Driver The input data is retimed on the rising edge of CLK+. If RTEN is connected to ground, the retiming function is disabled and the input data is directly connected to the output stage. Leave CLK+ and CLK- open when retiming is disabled. An internal, independent current source drives a constant 37mA to the modulation circuitry and any voltage above VEE on the MODSET pin adds to this. The input impedance of the MODSET pin is typically 20kΩ.
PAGE 9
10Gbps Modulator Driver MODEN PLRT 50Ω 50Ω 50Ω 50Ω 50Ω MAX3942 RTEN 50Ω OUTOUT+ CLK+ VEE CLKD Q 0 MUX DATA+ DATA- POLARITY PWC 1 50Ω IMOD 50Ω MAX3942 PWC+ VEE MODSET PWC2kΩ + VMODSET - VEE VEE Figure 4. Functional Diagram GND Interface Schematics Figures 5 and 6 show simplified input and output circuits of the MAX3942 modulator driver. To minimize inductance, keep the connections from OUT, GND, and VEE as short as possible. This is crucial for optimal performance.
PAGE 10
Exposed-Pad Package GND GND MAX3942 50Ω GND 50Ω GND OUT- The exposed pad on the 24-pin QFN provides a very low thermal resistance path for heat removal from the IC. The pad is also electrical ground on the MAX3942 and must be soldered to the circuit board ground for proper thermal and electrical performance. Refer to Maxim Application Note HFAN-08.1: Thermal Considerations of QFN and Other Exposed-Paddle Packages for additional information.