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LCP02-150M View Datasheet(PDF) - STMicroelectronics

Part Name
Description
MFG CO.
'LCP02-150M' PDF : 10 Pages View PDF
1 2 3 4 5 6 7 8 9 10
Technical information
2
Technical information
LCP02-150M
Figure 5. LCP02 concept behavior
Rs1
L1
GND
Ign
-Vbat Gn
Cn
TIP
V Tip
T2
T1
Th1
Th2
Igp
Gp +Vb
Cp
Rs2
L2
RING
GND
V Ring
Figure 5. shows the classical protection circuit using the LCP02-150M crowbar concept.
This topology has been developped to protect the new two-battery voltage SLICs. It allows
both positive and negative firing thresholds to be programmed. The LCP02-150M has two
gates (GN and GP). Gn is biased to negative battery voltage -Vbat, while GP is biased to the
positive battery voltage +Vb.
When a negative surge occurs on one wire (L1 for example), a current Ign flows through the
base of the transistor T1 and then injects a current in the gate of the thyristor Th1 which
fires. The entire surge current flows through the ground. After the surge, when the current
flowing through Th1 becomes less negative than the negative holding current, Th1 switches
off. This holding current IH- is temperature dependant as per Figure 2.
When a positive surge occurs on one wire (L1 for example), a current Igp flows through the
base of the transistor T2 and then injects a current in the gate of the thyristor Th2 which
fires. The entire surge current flows through the ground. After the surge, when the current
flowing through Th2 becomes less positive than the positive holding current IH+, Th2
switches off. This holding current IH+ is temperature dependant and is equal to 30 mA at
25° C.
The capacitors CN and CP are used to speed up the crowbar structure firing during the fast
surge rise or falling edges. This allows to minimize the dynamical breakover voltage at the
SLIC Tip and Ring inputs during fast surges. Please note that these capacitors are generally
available around the SLIC. To be efficient they have to be as close as possible to the LCP02-
150M gate pins (GN and GP) and to the reference ground track (or plan). The optimized
value for CN and CP is 220 nF.
The series resistors Rs1 and Rs2 represent the fuse, fuse resistors or the PTCs which are
needed to withstand the power contact or the power induction tests imposed by the country
standards. Taking this factor into account, the actual lightning surge current flowing through
the LCP02-150M is equal to:
I surge = Vsurge / (Rg + Rs)
Where:
Vsurge = peak surge voltage imposed by the standard.
Rg = series resistor of the surge generator
Rs = series resistor of the line card (e.g. PTC)
The LCP02-150M topology is particularly optimized for the new telecom applications such
as cable modem, fiber in the loop, WLL systems, and decentralized central office for
example. The schematics of Figure 6. and Figure 7. give the 2 most frequent topologies
used for these emergent applications.
6/10
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