10.7 Gbps Active Back-Termination,

Differential Laser Diode Driver

ADN2525

Rev. 0

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FEATURES

Up to 10.7 Gbps operation

Very low power: 670 mW (IBIAS = 40 mA, IMOD = 40 mA)

Typical 24 ps rise/fall times

Full back-termination of output transmission lines

Drives TOSAs with resistances ranging from 5 Ω to 50 Ω

PECL-/CML-compatible data inputs

Bias current range: 10 mA to 100 mA

Differential modulation current range: 10 mA to 80 mA

Automatic laser shutdown (ALS)

3.3 V operation

Compact 3 mm × 3 mm LFCSP package

Voltage input control for bias and modulation currents

XFP-compliant bias current monitor

Optical evaluation board available

APPLICATIONS

SONET OC-192 optical transceivers

SDH STM-64 optical transceivers

10 Gb Ethernet optical transceivers

XFP/X2/XENPAK/XPAK/MSA 300 optical modules

SR and VSR optical links

GENERAL DESCRIPTION

The ADN2525 laser diode driver is designed for direct modula-

tion of packaged laser diodes having a differential resistance

ranging from 5 Ω to 50 Ω. The active back-termination technique

provides excellent matching with the output transmission lines

while reducing the power dissipation in the output stage. The

back-termination in the ADN2525 absorbs signal reflections

from the TOSA end of the output transmission lines, enabling

excellent optical eye quality to be achieved even when the

TOSA end of the output transmission lines is significantly mis-

terminated. The small package provides the optimum solution

for compact modules where 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 power and extinction ratio control schemes,

including closed-loop control and look-up tables. The automatic

laser shutdown feature allows the user to turn on/off the bias

and modulation currents by driving the ALS pin with the

proper logic levels.

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

package specified from −40°C to +85°C.

FUNCTIONAL BLOCK DIAGRAM

50

Ω

IMOD

200

Ω

800

Ω

200

Ω

2

Ω

VCC

DATAP

DATAN

MSET

GND

BSET

IBMON

IBIAS

IMODP

IMODN

ADN2525

VCC

ALS

GND

VCC

VCC

50

Ω

50

Ω

200

Ω

800

Ω

Figure 1.