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CLP270M
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APPLICATION NOTE
1. INTRODUCTION
This device includes a primary protection level and is suitable for main distribution frames and line cards.
This protection concept is explained and, in addition, the CLP270M performances are analysed when
facing different surges as described in the BELLCORE GR 1089 recommendations.
Figure 1 is a simplified block diagram of a subscriber line protection that is commonly used.
This shows two different topologies :
I
A “primary protection” located on the Main Distribution Frame (MDF) eliminates coarsely the high energy
environmental disturbances (lightning transients and AC power mains disturbances)
I
A “secondary protection” located on the line card includes a primary protection level (first stage) and a
residualprotection(secondstage)which eliminatesfinelytheremainingtransientsthathavenotbeentotally
suppressed by the first stage.
2. STMicroelectronics CLP270M CONCEPT
2.1. Evolution of the SLIC protection
Over the years, the silicon protection performances have considerably changed.
The first generation of products like SMTHBTxx and SMTHDTxx offered fixed overvoltage protection
against surges on either TIP or RING line in four
packages.
The
following
generation
like
THBTxx
and
THDTxx still offered fixed overvoltage protection
against surges on both TIP and RING lines in two
packages.
The next step was the introduction of the
LCP1511D which brought the advantage of full
programmable voltage.
Today, the CLP270M combines the features of all
the previous generations. In addition to that, it
offers an overcurrent detection when operating in
speech mode and also a Failure Status output
signal.
CLP270M
CLP270M
SLIC
SLIC
THDTxx
LCPor
or
LCDP1511D
“PRIMARY PROTECTION”
“SECONDARY PROTECTION”
“SECONDARY PROTECTION”
Telecommunication
line
Telecommunication
line
MDF
EXCHANGE
EXCHANGE
LINE CARD
LINE CARD
MDF
Fig. 1:
Subscriber line protection topology
Line card
operating
conditions
V
I
-I
+I
SWON
SWON
Programmable
thanks to an
external resistor
Programmable
thanks to any
external voltage
reference
Fig. 2:
Line card protection