21
littelfuse.com
LEARN MORE LEARN MORE
Littelfuse P-0S-LRP
Voice-DS1 SIDACtor
®
Protection Thyristors
Littelfuse 461
TeleLink
®
Surface
Mount Fuses
PoE Protection
Power over Ethernet (15.4W), PoE+ (30W), PoE++ (90W))
powers remote devices via the Ethernet cable (Figure 5).
Littelfuse suggests that designers employ TeleLink fuses
for overcurrent protection, such as the 461 series. For
voltage protection, Littelfuse suggests that one utilize a
TVS diode. TVS diodes can be used across the center
tap signal pair and a second one across the center tap
spare pair. The TVS diode can be chosen based on one's
search needs for the specific application. We have 400W,
600W, 1500W, or 3kW. The TVS diode array Littelfuse
recommends you looking at is the SMCJ series.
For any Ethernet application, the optimal
protection depends on where it's being used
and the amount of exposure that that location
might have to electrical hazards. Standard
GR-1089 provides an excellent reference
to what testing could be done to select the
right components and know that one has
adequate protection. One of the tests, GR-
1089, requires a power cross test in how the
circuit is protected. It requires a solution such
as the 461 fuses, which can not only protect for
a power cross event as a short circuit type of
event, but it would also be able to withstand the
surge levels that are adequate for that outdoor
connector. SIDACtors provide surge protection
on the lines that have the power. Ghost power
created on PoE gets separated off and fed into
a power controller to be used as real DC power,
and those lines are protected primarily by a
SIDACtor.
Littelfuse is the company to go to for solutions to protect
industrial communication equipment. Whether you rely
on RS-485 and Ethernet connections, its wide variety of
protection solutions keep your systems up and running in
even the most challenging environments. ■
"
"
Figure 5: PoE Port Protection. (Source: Littelfuse)
For any Ethernet application, the
optimal protection depends on where
it's being used and the amount of
exposure that that location might have
to electrical hazards.
