tisp4240m3 Bourns, Inc., tisp4240m3 Datasheet - Page 8

• Manufacturer Part Number: tisp4240m3
• Description: Bidirectional Thyristor Overvoltage Protectors - Power Innovations Ltd
• Manufacturer: Bourns, Inc.

TISP4070M3LM THRU TISP4095M3LM, TISP4125M3LM THRU TISP4220M3LM,
TISP4240M3LM THRU TISP4400M3LM
BIDIRECTIONAL THYRISTOR OVERVOLTAGE PROTECTORS
NOVEMBER 1997 - REVISED APRIL 1999
deployment
impulse testing
P R O D U C T
8
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).
In Figure 12, protector Th1 limits the maximum voltage between the two conductors to ±V
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
individual protector. Protector Th1 limits the maximum voltage between the two conductors to its ±V
value. If the equipment being protected has all its vulnerable components connected between the conductors
and ground, then protector Th1 is not required.
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.
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.
For the FCC Part 68 10/560 waveform the following values result. The minimum total circuit impedance is
800/75 = 10.7
resistance value of 10.7 - 8 = 2.7 . After allowing for tolerance, a 3
10/160 waveform needs a standard resistor value of 5.6
If the impulse generator current exceeds the protectors current rating then a series resistance can be used to
Figure 12. TWO POINT PROTECTION
GR-1089-CORE
FCC Part 68
(March 1998)
I3124
ITU-T K20/K21
† FCC Part 68 terminology for the waveforms produced by the ITU-T recommendation K21 10/700 impulse generator
STANDARD
I N F O R M A T I O N
and the generators fictive impedance is 800/100 = 8 . This gives a minimum series
PEAK VOLTAGE
SETTING
Th1
2500
1000
1500
1500
1000
1500
1500
4000
800
V
APPLICATIONS INFORMATION
WAVE FORM
VOLTAGE
10/1000
9/720 †
9/720 †
0.5/700
10/160
10/560
10/700
2/10
µs
PEAK CURRENT
VALUE
37.5
37.5
37.5
500
100
200
100
100
25
A
per conductor. These would be R1a and R1b in
Figure 13. MULTI-POINT PROTECTION
WAVE FORM
CURRENT
10/1000
5/320 †
5/320 †
0.2/310
10/160
10/560
5/310
2/10
µs
±10% resistor would be suitable. The
Th1
25 °C R ATING
TISP4xxxM3
300
120
100
100
100
100
75
A
50
Th3
Th2
RESISTANCE
SERIES
2x5.6
11
3
0
0
0
0
(BO)
(BO)
. This
of the
(BO)