®
TSIxxB1
TERMINAL SET INTERFACE
PROTECTION AND DIODE BRIDGE
Application Specific Discretes
A.S.D.™
MAIN APPLICATION
Telecom equipment requiring combined
protection against transient overvoltages and
rectification by diode bridge :
Telephone set
Base station for cordless set
Fax machine
Modem
Caller Id equipment
Set top box
s
s
s
s
s
SO-8
s
DESCRIPTION
The TSIxxB1 provides the diode bridge and the
crowbar protection function that can be found in
most of telecom terminal equipment.
Integrated monolithically within a SO-8 package,
this ASD™ device allows space saving on the
board and greater reliability.
FEATURES
STAND-OFF VOLTAGE FROM 62V TO 265V
PEAK PULSE CURRENT : 30 A (10/1000
µs)
MAXIMUM DC CURRENT : I
F
= 0.2 A
HOLDING CURRENT :150 mA
s
s
s
s
SCHEMATIC DIAGRAM
1
2
3
4
8
7
6
5
IN ACCORDANCE WITH THE FOLLOWING
STANDARDS :
CCITT K17 - K20
VDE 0433
CNET
Bellcore
TR-NWT-000974:
10/700
5/310
10/700
5/310
0.5/700
0.2/310
µs
µs
µs
µs
µs
µs
1.5 kV
38A
2 kV
40A(*)
1.5 kV
38A
1 kV
30A(*)
2.5 kV
75A (*)
BENEFITS
s
s
s
10/1000
µs
10/1000
µs
FCC Part 68
2/10
µs
2/10
µs
MIL STD883C Method 3015-6
(*) with series resistor or PTC.
TM: ASD is trademarks of STMicroelectronics.
s
Diode bridge for polarity guard and crowbar
protection within one device.
Single chip for greater reliability
Reduces component count versus discrete
solution
Saves space on the board
October 2003 - Ed: 4
1/9
TSIxxB1
TYPICAL APPLICATION
PTC
Telecom terminals have a diode bridge for polarity
guard, located at the line interface stage. They
also have above this diode bridge one crowbar
protection device that is mandatory to prevent
atmospheric effects and AC mains disturbances
from damaging the electronic circuitry that follows
the diode bridge.
ST proposes a one chip device that includes both
protection and diode bridge. This is the concept of
the TSIxxB1 devices.
Fig. 1 :
The various uses of the TSIxxB1 in a conventional telecom network
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TSIxxB1
ELECTRICAL PARAMETERS
The V
RM
value corresponds to the maximum
voltage of the application in normal operation. For
instance, if the maximum line voltage is ranging
between
100V
RMS
of ringing plus 48V of battery
voltage, then the protection chosen for this applica-
tion shall have a V
RM
close to 200V.
The V
BO
is the triggering voltage. This indicates
the voltage limit for which the component
short-circuits. Passing this V
BO
makes the device
turn on.
The I
BO
is the current that makes the device turn
on. Indeed, if we want a Trisil to be turned on not
only the voltage across it shall pass the V
BO
value
but the current through it shall also pass the I
BO
value.
In other words, if a voltage surge occurring on the
line is higher than the V
BO
value of a Trisil,
whereas the line surge current is limited to a value
that does not exceed the Trisil’s I
BO
value, then the
Trisil will never turn into short circuit. At this time
the surge will be clamped by the Trisil.
Anyhow the electronic circuitry located after the
Trisil will always be protected whatever the Trisil
state is (crowbar or clamping mode).
The I
H
stands for the holding current. When the
Trisil is turned on, as soon as the crossing current
surge gets lower than this I
H
value, the Trisil
protection device turns back in its idle state.
Remark : for this reason the Trisil ‘s I
H
value shall
be chosen higher than what the maximum telecom
line current can be.
Fig. 2 :
Test circuit for the CCITT K17 recommendations
TSIxxB1 BEHAVIOUR WITH REGARD TO
SURGE STANDARD :
The TSIxxB1 is able to replace both diode bridge
and usual discrete protection on telecom
terminals. Furthermore it complies with the CCITT
K17 recommendations :
10/700
µs
waveform surge test,
1.5kV
AC power induction test
AC power contact test
Ω
3/9
TSIxxB1
TEST # 1
LIGHTNING SIMULATION
This test concerns the 10/700
µs
waveform surge,
±
1.5 kV.
Fig. 2
: 10/700
µs
waveform surge generator circuit
The surge generator used for the test has the
following circuitry (fig.2).
Ω
Ω
Ω
The behaviour of the TSI200B1 to this lightning surge is given below (fig. 3).
Fig. 3 :
Voltage across the TSI200B1 at the + and - terminations and current throught it
for a 1.5 kV positive surge (fig.3a) and negative surge (fig. 3b)
These curves show the peak voltage the surge
generates across the TSI200B1 + and -
terminations. This lasts a short time (′ 2
µs)
and
after, as the internal protection gehaves like a
short circuit. The voltage drop across the TSIxxB1
becomes a few volts. In the meanwhile all the
surge current flows in the protection.
As far as the 10/700
µs
waveform surge test is
concerned,the TSIxxB1 withstand the ±1.5 kV test.
4/9
TSIxxB1
TEST # 2
AC POWER INDUCTION TEST
This test simulates the induction phenomena that
can happen between telecom lines and AC mains
lines (fig. 4).
TEST #3
AC POWER CONTACT TEST
This test simulates the direct contact between the
telecom lines and the AC mains lines.
The AC power contact test consists in applying
240V
RMS
through a 10Ω PTC during 15 minutes
long on the device under test. The CCITT K17
recommendation specifies an internal generator
impedance allowing 10 A
RMS
when in short circuit.
The behavior of the TSI200B1 with respect to this
surge is given in figure 6.
Fig. 6 :
Voltage at the TSI200B1 + & - terminations
and the current through it.
Fig. 4 :
AC power induction test circuit
Part #1
test conditions :
V
RMS
= 240 V
R = 600
Ω
t = 0.2 s
V
RMS
= 600 V
R = 600
Ω
t = 0.2 s
Part #2
test conditions :
Fig. 5 :
Voltage at the + and - terminations of the
TSI200B1, and current through it
while test part 1 is applied.
The figure 6 shows that after 250ms there is no
current anymore flowing through the TSI200B1
device. This is due to the action of the serial PTC
that limits the current through the line. This PTC is
mandatory for this test. It can also be replaced by a
fuse or any other serial protection that “opens” the
line loop under AC contact test.
The TSIxxB1 withstand the AC power induction
test in both cases.
5/9
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