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CLP270M
OVERVOLTAGE AND OVERCURRENT
PROTECTION FOR TELECOM LINE
Application Specific Discretes
A.S.D.
PRELIMINARY DATASHEET
PowerSO-10
TM
SCHEMATIC DIAGRAM
MAIN APPLICATIONS
Any telecom equipment submitted to transient
overvoltages and lightning strikes such as :
s
Analog and ISDN line cards
s
PABX
s
Main Distribution Frames
s
Primary protection modules
DESCRIPTION
The
CLP270M
is
designed
to
protect
telecommunication equipment. It provides both a
transient
overvoltage
protection
and
an
overcurrent protection.
It is housed in a PowerSO-10
TM
package.
FEATURES
s
DUAL BIDIRECTIONAL PROTECTION DEVICE.
s
HIGH PEAK PULSE CURRENT :
Ipp = 100A (10/1000
s SURGE)
Ipp = 500A (2/10
s SURGE)
s
MAX. VOLTAGE AT SWITCHING-ON : 380V
s
MIN. CURRENT AT SWITCHING-OFF : 150mA
s
FAILURE STATUS OUTPUT PIN
BENEFITS
s
Both primary and secondary protection levels in
one device.
s
Voltage and current controlled suppression.
s
Surface
Mounting
with
PowerSO-10
TM
p a c k a g e .
s
Line card cost reduction thanks to the very low
power rating of external components required :
balanced resistors, ring relay, low voltage SLIC
protection.
NC
FS
TIP
S
RING
S
TIP
L
TIP
L
TIP
L
RING
L
RING
L
RING
L
TAB is connected to GND
1
July 2003 - Ed: 7C
CLP270M
2/24
BLOCK DIAGRAM
270
270
Pin
Symbol
Description
1
FS
Failure Status
2
TIPS
TIP (SLIC side)
3 / 4 / 5
TIPL
TIP (Line side)
6 / 7 / 8
RINGL
RING (Line side)
9
RINGS
RING (SLIC side)
10
NC
Not connected
TAB
GND
Ground
COMPLIES WITH THE
FOLLOWING STANDARDS:
Peak Surge
Voltage
(V)
Voltage
Waveform
(
s)
Current
Waveform
(
s)
Admissible
Ipp
(A)
Necessary
Resistor
(
)
ITU K20
6000
10/700
5/310
150
-
VDE0433
6000
10/700
5/310
150
-
VDE0878
4000
1.2/50
1/20
100
-
IEC61000-4-5
6000
4000
10/700
1.2/50
5/310
8/20
150
100
-
-
FCC Part 68, lightning surge
type A
1500
800
10/160
10/560
10/160
10/560
200
100
-
-
FCC Part 68, lightning surge
type B
100
9/720
5/320
25
-
BELLCORE TR-NWT-001089
First level
2500
1000
2/10
10/1000
2/10
10/1000
500
100
-
-
BELLCORE TR-NWT-001089
Second level
5000
2/10
2/10
500
-
CNET l31-24
4000
0.5/700
0.8/310
100
-
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 :
s
A "primary protection" located on the Main Distribution Frame (MDF) eliminates coarsely the high energy
environmental disturbances (lightning transients and AC power mains disturbances)
s
A "secondary protection" located on the line card includes a primary protection level (first stage) and a
residual protection (second stage) which eliminates finely the remaining transients that have not been totally
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
or
LCP1511D
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
CLP270M
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The figure 2 summarizes the firing modes of the CLP270M which basically hold the SLIC inside its correct
voltage and current values.
2.2 Application circuit: CLP270M in line card.
Figure 3 above shows the topology of a protected analog subscriber line at the exchange side. The
CLP270M is connected to the ring relay via two balanced Rp resistors, and to the Subscriber Line Interface
Circuit. A second device is located near the SLIC : it can be either a LCP1511D, a THDT series or a
LCDP1511D.
These two devices are complementary and their functions are explained below :
s
The first stage based on CLP270M manages the high power issued from the external surges. When
used in ringing mode, the CLP270M operates in voltage mode and provides a symmetrical and
bidirectional overvoltage protection at +/- 270 V on both TIP and RING lines. When used in speech
mode, the CLP270M operates in current mode and the activation current of the CLP270M is adjusted
by R
sense
.
s
The second stage is the external voltage reference device which defines the firing threshold voltage
during the speech mode and also assumes a residual power overvoltage suppression. This protection
stage can be either a fixed or programmable breakover device. The THDTxx family acts as a fixed
breakover device while the LCP1511D or the LCDP1511D operates as a programmable protection.
Thanks to this topology,
the surge current in the line is reduced after the CLP270M. Because the
remaining surge energy is low, the power ratings of Rp, the ring relay contacts and the external voltage
reference circuit can be downsized. This results in a significant cost reduction.
RINGS
-Vbat
-Vbat
Rp
Rsense
TIP
1
1
2
2
SLIC
(*)
(*) LCP1511D or THDT series or LCDP1511D
Ov v
ref
er oltage
erence
(+/- 270 V)
Overvoltage
detector
Overcurrent
detector
OR
Overvoltage
reference
(+/- 270 V)
Overvoltage
detector
Overcurrent
detector
OR
TIPL
TIPS
RINGL
FS
GND
SW3 SW1
SW4 SW2
Rsense
Rp
Ring
Generator
Fuse
Fuse
TIP
RING
External
voltage
reference
RING
I
Fig. 3 : CLP270M in line card
CLP270M
5/24
2.3. Ringing mode
In ringing mode (Ring relay in position 2), the only protection device involved is the CLP270M.
In normal conditions, the CLP270M operates in region 1 of A1 curve, and is idle.
If an overvoltage occuring between TIP (or RING) and GND reaches the internal overvoltage reference
(+/- 270 V), the CLP270M acts and the line is short-circuited to GND. At this time the operating point
moves to region 2 for positive surges (region 3 for negative surges). Once the surge current falls below
the switch off current I
SWOFF
, the device returns to its initial state (region 1).
For surges occuring between TIP and RING, the CLP270M acts in the same way. This means that the
CLP270M ensures a tripolar protection.
When used alone, the CLP270M acts at the internal overvoltage reference level (+/- 270 V). Furthermore, it
is possible to adjust this threshold level to a lower voltage by using:
Rsense
Rp
1
2
Overvoltage
reference
(+/- 270 V)
Overvoltage
detector
Overcurrent
detector
OR
TIPL
TIPS
FS
SW3 SW1
Fuse
TIP
GND
I
LG
V
LG
1/2 CLP270M
I
LG
V
1
2
3
-270
+270
A1
Fig. 4: Switching by voltage during ringing mode.
RINGS
Rsense
Rsense
1
2
Overvoltage
reference
(+/- 270 V)
Overvoltage
detector
Overcurrent
detector
OR
Overvoltage
reference
(+/- 270 V)
Overvoltage
detector
Overcurrent
detector
OR
TIPL
TIPS
RINGL
FS
GND
SW3 SW1
SW4 SW2
1
2
Fuse
Fuse
TIP
RING
VZ1
VZ2
VZ3
VZ4
Rp
Rp
Fig. 5a: Method to adjust the reference voltage.
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