TISP4070H3LM THRU TISP4095H3LM, TISP4125H3LM THRU TISP4220H3LM,
TISP4240H3LM THRU TISP4400H3LM
BIDIRECTIONAL THYRISTOR OVERVOLTAGE PROTECTORS
NOVEMBER 1997 - REVISED APRIL 1999
APPLICATIONS INFORMATION
deployment
These devices are two terminal overvoltage protectors. They may be used either singly to limit the voltage
between two conductors (Figure 12) or in multiples to limit the voltage at several points in a circuit (Figure 13).
Th3
Th1
Th1
Th2
Figure 12. TWO POINT PROTECTION
Figure 13. MULTI-POINT PROTECTION
In Figure 12, protector Th1 limits the maximum voltage between the two conductors to ±V
(BO)
. This
configuration is normally used to protect circuits without a ground reference, such as modems. In Figure 13,
protectors Th2 and Th3 limit the maximum voltage between each conductor and ground to the ±V
(BO)
of the
individual protector. Protector Th1 limits the maximum voltage between the two conductors to its ±V
(BO)
value. If the equipment being protected has all its vulnerable components connected between the conductors
and ground, then protector Th1 is not required.
impulse testing
To verify the withstand capability and safety of the equipment, standards require that the equipment is tested
with various impulse wave forms. The table below shows some common values.
PEAK VOLTAGE
STANDARD
SETTING
V
GR-1089-CORE
2500
1000
1500
FCC Part 68
(March 1998)
I3124
ITU-T K20/K21
800
1500
1000
1500
1500
4000
VOLTAGE
WAVE FORM
µs
2/10
10/1000
10/160
10/560
9/720 †
9/720 †
0.5/700
10/700
PEAK CURRENT
VALUE
A
500
100
200
100
37.5
25
37.5
37.5
100
CURRENT
WAVE FORM
µs
2/10
10/1000
10/160
10/560
5/320 †
5/320 †
0.2/310
5/310
TISP4xxxH3
25 °C RATING
A
500
100
250
160
200
200
200
200
SERIES
RESISTANCE
Ω
0
0
0
0
0
0
0
† FCC Part 68 terminology for the waveforms produced by the ITU-T recommendation K21 10/700 impulse generator
If the impulse generator current exceeds the protectors current rating then a series resistance can be used
to reduce the current to the protectors rated value and so prevent possible failure. The required value of
series resistance for a given waveform is given by the following calculations. First, the minimum total circuit
impedance is found by dividing the impulse generators peak voltage by the protectors rated current. The
impulse generators fictive impedance (generators peak voltage divided by peak short circuit current) is then
subtracted from the minimum total circuit impedance to give the required value of series resistance. In some
cases the equipment will require verification over a temperature range. By using the rated waveform values
from Figure 11, the appropriate series resistor value can be calculated for ambient temperatures in the range
of -40 °C to 85 °C.
PRODUCT
8
INFORMATION
POINN [ POWER INNOVATIONS LTD ]
