11.3 Gbps, Active Back-Termination,

Differential Laser Diode Driver

ADN2531

Rev. 0

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FEATURES

3.3 V operation

Up to 11.3 Gbps operation

Typical 26 ps rise/fall times

Bias current range: 10 mA to 100 mA

Differential modulation current range: 10 mA to 80 mA

Voltage input control for bias and modulation currents

Data inputs sensitivity: 150 mV p-p differential

Automatic laser shutdown (ALS)

Crosspoint adjustment (CPA)

VCSEL, FP, DFB laser support

SFF/SFP/XFP/SFP+ MSA compliant

Optical evaluation board available

Compact, 3 mm × 3 mm LFCSP

APPLICATIONS

Optical transmitters, up to 11.3 Gbps, for SONET/SDH,

Ethernet, and Fibre Channel applications

SFF/SFP/SFP+/XFP/X2/XENPAK/XPAK MSA compliant

300-pin optical modules, up to 11.3 Gbps

GENERAL DESCRIPTION

The ADN2531 laser diode driver can work with directly

modulated laser diodes, including vertical-cavity surface-emitting

laser (VCSEL), Fabry-Perot (FP) lasers, and distributed feedback

(DFB) lasers, with a differential loading resistance ranging from

5 Ω to 140 Ω. The active back-termination in the ADN2531

absorbs signal reflections from the laser diode side of the output

transmission lines, enabling excellent optical eye quality even when

the TOSA end of the output transmission lines is significantly

mismatched. The ADN2531 is a SFP+ MSA-compliant device,

and its small package and enhanced ESD protection provides

the optimum solution for compact modules in which laser

diodes are packaged in low pin-count optical subassemblies.

The modulation and bias currents are programmable via the

MSET and BSET control pins. By driving these pins with control

voltages, the user has the flexibility to implement various average

optical power and extinction ratio control schemes, including a

closed-loop or a look-up table control. The automatic laser shut-

down (ALS) feature allows turning the bias on and off while

simultaneously modulating currents by driving the ALS pin with

a low voltage transistor-to-transistor logic (LVTTL) source.

The product is available in a space-saving, 3 mm × 3 mm LFCSP

package and operates from −40°C to +100°C.

FUNCTIONAL BLOCK DIAGRAM

100

Ω

200

Ω

400

Ω

200

Ω

10

Ω

VCC

DATAP

DATAN

MSET

GND

BSET

IBMON

IBIAS

IMODP

IMODN

ADN2531

VCC

ALS

GND

VCC

VCC

50

Ω

50

Ω

CPA

200

Ω

800

Ω

CROSSPOINT

ADJUST

Figure 1.