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
50ΩIMOD
200Ω
800Ω
200Ω 2Ω
VCC
DATAP
DATAN
MSET GND BSET
IBMON
IBIAS
IMODP
IMODN
ADN2525
VCC ALS
GND
VCC
VCC
50Ω 50Ω
200Ω
800Ω
02461-001

Figure 1.