EVAL-ADN2525-OP_15 Datasheet, PDF (5/8 Pages) Analog Devices – Optical Evaluation Kit for the ADN2525

EVAL-ADN2525-NT/ADN2525-OP
USING THE EVALUATION BOARD PCB LAYOUT IN
AN OPTICAL TRANSMITTER DESIGN
The evaluation kit PCB is fabricated using FR4 (Polyclad PCL-
FR-370HR) with 4.5 mil dielectric thickness between the top-
side signal and ground layers. When using the evaluation board
PCB layout as a guide for designing an optical transmitter, it is
recommended that the same dielectric material and thickness
be used and the PCB layout associated with the ADN2525, the
ac-coupling components, and the TOSA be copied exactly. This
includes features such as component pad positions and sizes,
track widths and lengths, via sizes, and positions. These features
affect the high frequency performance in ways that are difficult
to predict; therefore, changing them increases the risk of losing
some mask margin performance. Following this recommenda-
tion gives the highest likelihood that eye diagram performance
measured on the evaluation board is reproduced in the optical
transmitter (ignoring any performance loss contributed by
retiming or other circuitry that precedes the ADN2525). It is
possible that changing the PCB dielectric material or making
small changes to the PCB layout causes negligible degradation
in the performance or even improves the performance. How-
ever, this is difficult to predict.
1.059
2.974
0.098
2.82
0.27 0.6
2.606
1.496
2.276
2.106
THERMISTOR
CASE GND
LD ANODE
LD CATHODE
CASE GND
MPD CATHODE
1.776
0.506
0.886
0
0.155
0.27
0
0.6
0.87
NOTES
1. DIMENSIONS SHOWN IN INCHES.
0.095
0.964
Figure 3. Evaluation Board Outline
0.176
3.128
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