SPFMIT302 Avago Technologies, SPFMIT302 Datasheet - Page 8

• Manufacturer Part Number: SPFMIT302
• Description: Plastic Fiber Optic Transmitter For Most
• Manufacturer: Avago Technologies

Top Layer with 180˚ version of the pigtail:
Bottom Layer (seen from the top side of the PCB):
Other items
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8
The shown circuit for the –3dB attenuation is just a proposal. Also any other circuit which can double the value of
Rext is permitted.
Due to the fact that the optical average level jumps if the power control signal (/-3dB) is toggled there can occur
LOCK/coding – errors at the following device for a short time. This is not very critical, since it does occur only in
diagnosis mode. After a time of 10ms the device should lock again if the optical attenuation between the devices is
not too high.
The Rx and Tx signals can be measured by using standard probes (>1M/<10pF). However, if the signal quality is very
bad and the LOCK signal of the MOST chip is flaky connecting a passive probe to the Rx signal can cause the MOST
chip to lock better or worse to the signal. This is due to the capacitance of the analog probe which is usually in the
range of 8..12pF and shifts the phase and PWD of the signal. In this case an active probe with a capacitance of less
than 1pF is recommended.
The reference test board which corresponds to the layout examples above is available at the Oasis Silicon System
AG.
Bottom Layer: Bottom side / positions