Overcurrent Protection
Advantages include:
•
•
•
•
•
•
Elimination of series line resistance enabling longer loop lengths
Precise longitudinal balance allowing better transmission quality
Robust surge performance which eliminates costly down time due to nuisance blows
Greater surge ratings than resettable devices, ensuring regulatory compliance
Non-degenerative performance
Available in surface mount packaging which uses less Printed Circuit Board (PCB) real
estate, eliminates mixed technologies, and reduces manufacturing costs
Weaknesses
Because a fuse does not reset, consideration should be given to its use in applications
where multiple fault occurrences are likely. For example, AC strip protectors and ground
fault interrupting circuits (GFIC) are applications in which an alternative solution might be
more prudent.
Applications
Telecommunications equipment best suited for a fuse is equipment that requires surface
mount technology, accurate longitudinal balance, and regulatory compliance without the
use of additional series line impedance.
Selection Criteria
For circuits that do not require additional series resistance, the surge current rating (IPP) of
the TeleLink SM fuse should be greater than or equal to the surge currents associated with
the lightning immunity tests of the applicable regulatory requirement (IPK).
IPP OꢀIPK
For circuits that use additional series resistance, the surge current rating (IPP) of the
TeleLink SM fuse should be greater than or equal to the available surge currents associated
with the lightning immunity tests of the applicable regulatory requirement (IPK (available)).
IPP OꢀIPK (available)
The maximum available surge current is calculated by dividing the peak surge voltage (VPK
by the total circuit resistance (RTOTAL).
)
IPP OꢀIPK (available) = VPK/RTOTAL
For longitudinal surges (Tip-Ground, Ring-Ground), RTOTAL is calculated for both Tip and
Ring.
R
TOTAL = RTIP + RSOURCE
RTOTAL = RRING + RSOURCE
For metallic surges (Tip-Ring):
R
TOTAL = RTIP + RRING + RSOURCE
© 2002 Teccor Electronics
5 - 15
http://www.teccor.com
+1 972-580-7777
®
SIDACtor Data Book and Design Guide
TECCOR [ TECCOR ELECTRONICS ]
