Specifications are subject to change without notice. 105
JANUARY 1999 - REVISED MAY 2002
Standard
Peak Voltage
Setting
V
Voltage
Waveform
µs
Peak Current
Value
A
Current
Waveform
µs
TISP3xxxH3
25 °C Rating
A
Series
Resistance
Ω
GR-1089-CORE 2500 2/10 500 2/10 500 0
1000 10/1000 100 10/1000 100
FCC Part 68
(March 1998)
1500 10/160 200 10/160 250 0
800 10/560 100 10/560 160 0
1500 9/720 †37.5 5/320 †200 0
1000 9/720 †25 5/320 †200 0
I3124 1500 0.5/700 37.5 0.2/310 200 0
ITU-T K.20/K.21 1500
4000 10/700 37.5
100 5/310 200 0
† FCC Part 68 terminology for the waveforms produced by the ITU-T recommendation K.21 10/700 impulse generator
Impulse Testing
TISP3xxxH3SL Overvoltage Protector Series
APPLICATIONS INFORMATION
AC Power Testing
Capacitance
Normal System Voltage Levels
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.
If the impulse generator current exceeds the protector’s current rating, then a series resistance can be used to reduce the current to the
protector’s rated value to 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 generator’s peak voltage by the protector’s rated
current. The impulse generator’s fictitious impedance (generator’s 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 10, the appropriate series resistor value can be calculated for ambient
temperatures in the range of -40 °C to 85 °C.
The protector can withstand the G return currents applied for times not exceeding those shown in Figure 8. Currents that exceed these times
must be terminated or reduced to avoid protector failure. Fuses, PTC (Positive Temperature Coefficient) resistors and fusible resistors are
overcurrent protection devices which can be used to reduce the current flow. Protective fuses may range from a few hundred milliamperes to
one ampere. In some cases, it may be necessary to add some extra series resistance to prevent the fuse opening during impulse testing. The
current versus time characteristic of the overcurrent protector must be below the line shown in Figure 8. In some cases, there may be a further
time limit imposed by the test standard (e.g. UL 1459 wiring simulator failure).
The protector characteristic off-state capacitance values are given for d.c. bias voltage, VD, values of 0, -1 V, -2 V, and -50 V. Where possible,
values are also given for -100 V. Values for other voltages may be calculated by multiplying the VD = 0 capacitance value by the factor given in
Figure 6. Up to 10 MHz, the capacitance is essentially independent of frequency. Above 10 MHz, the effective capacitance is strongly
dependent on connection inductance. In many applications, the typical conductor bias voltages will be about -2 V and -50 V. Figure 7 shows
the differential (line unbalance) capacitance caused by biasing one protector at -2 V and the other at -50 V.
The protector should not clip or limit the voltages that occur in normal system operation. For unusual conditions, such as ringing without the
line connected, some degree of clipping is permissible. Under this condition, about 10 V of clipping is normally possible without activating the
ring trip circuit. Figure 9 allows the calculation of the protector VDRM value at temperatures below 25 °C. The calculated value should not
be less than the maximum normal system voltages. The TISP3290H3, with a VDRM of 220 V, can be used for the protection of ring generators
producing 105 V rms of ring on a battery voltage of -58 V. The peak ring voltage will be 58 + 1.414*105 = 206.5 V. However, this is the open
circuit voltage and the connection of the line and its equipment will reduce the peak voltage.