CLP200M Datasheet, PDF (3/21 Pages) STMicroelectronics – OVERVOLTAGE AND OVERCURRENT PROTECTION FOR TELECOM LINE

APPLICATION NOTE
1. INTRODUCTION
The aim of this section is to show the behavior of
our new telecom line protectiondevice. 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 CLP200M performances are analysed when
facing different surges as described in the CCITT
recommendations.
Fig. 1 : Subscriber line protection topology
telecommunication
line
”PRIMARY PROTECTION”
CLP200M
MDF
”SECONDARY PROTECTION”
SLIC
LINE CARD
EXCHANGE
CLP200M
2. SGS-THOMSON CLP200M CONCEPT
2.1 Evolution of the SLIC protection
Over the years, the silicon protection per-
formances have considerably changed.
The first generation of products like SMTHBTxx
and SMTHDTxx offered fixed overvoltage protec-
tion 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
package s.
The next step was the introduction of the
LCP1511D which brought the advantage of full
programmable voltage.
Today, the CLP200M combines the features of all
the previous generations. In addition to that, it of-
fers an overcurrent detection when operating in
speech mode and also a Failure Status output sig-
nal.
telecommunication
line
MDF
”SECONDARY PROTECTION”
CLP200M
THDTxx or
LPC1511D
or LB200B
SLIC
LINE CARD
EXCHANGE
Figure 1 is a simplified block diagram of a sub-
scriber line protection that is mainly used so far.
This shows two different things :
A ”primary protection” located on the Main Distri-
bution Frame (MDF) eliminates coarsely the high
energy environmental disturbances (lightning
transients and AC power mains disturbances)
A ”secondary protection” located on the line card
includes a primary protectionlevel (first stage)and
a residual protection (second stage) which elimi-
nates finely the remaining transients that have not
beentotally suppressed by the first stage.
The CLP200M can be used both in MDFs and in
line cards. In that case, any line card may be
swapped from one MDF to another one without re-
ducing the efficiency of the whole system protec-
tion.
The CCITT requirements are different for these
two protection locations (MDFs and line cards).
Concerning the ”primary protection”, the CCITT re-
quires a 4kV, 10/700µs surge test whereas the
”secondary protection” has to withstand a 1kV,
10/700µs surge test.
The explanations which follow are basically
covering the line card application.
Fig. 2 : Line card protection
I
Programmable thanks to
any external voltage reference
+ I _SWON
Programmable thanks to
an external resistor
V
- I _SWON
Line card operating conditions
The figure 2 summarizes the performance of the
CLP200M which basically holds the SLIC inside its
correct voltage and current values.
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