TISP3xxxF3 (HV) Overvoltage Protector Series
APPLICATIONS INFORMATION
Electrical Characteristics
The electrical characteristics of a TISP
®
device are strongly dependent on junction temperature, TJ. Hence, a characteristic value will
depend on the junction temperature at the instant of measurement. The values given in this data sheet were measured on commercial
testers, which generally minimize the temperature rise caused by testing. Application values may be calculated from the parameters’
temperature coefficient, the power dissipated and the thermal response curve, Z
θ
(see M. J. Maytum, “Transient Suppressor Dynamic
Parameters.” TI Technical Journal, vol. 6, No. 4, pp. 63-70, July-August 1989).
Lightning Surge
Wave Shape Notation
Most lightning tests, used for equipment verification, specify a unidirectional sawtooth waveform which has an exponential rise and an
exponential decay. Wave shapes are classified in terms of peak amplitude (voltage or current), rise time and a decay time to 50 % of
the maximum amplitude. The notation used for the wave shape is
amplitude, rise time/decay time.
A 50 A, 5/310 µs wave shape would
have a peak current value of 50 A, a rise time of 5 µs and a decay time of 310 µs. The TISP
®
surge current graph comprehends the
wave shapes of commonly used surges.
Generators
There are three categories of surge generator type, single wave shape, combination wave shape and circuit defined. Single wave shape
generators have essentially the same wave shape for the open circuit voltage and short circuit current (e.g. 10/1000 µs open circuit
voltage and short circuit current). Combination generators have two wave shapes, one for the open circuit voltage and the other for the
short circuit current (e.g. 1.2/50 µs open circuit voltage and 8/20 µs short circuit current). Circuit specified generators usually equate to
a combination generator, although typically only the open circuit voltage waveshape is referenced (e.g. a 10/700 µs open circuit voltage
generator typically produces a 5/310 µs short circuit current). If the combination or circuit defined generators operate into a finite resis-
tance, the wave shape produced is intermediate between the open circuit and short circuit values.
Current Rating
When the TISP
®
device switches into the on-state it has a very low impedance. As a result, although the surge wave shape may be
defined in terms of open circuit voltage, it is the current wave shape that must be used to assess the required TISP
®
surge capability.
As an example, the ITU-T K.21 1.5 kV, 10/700 µs open circuit voltage surge is changed to a 38 A, 5/310 µs current waveshape when
driving into a short circuit. Thus, the TISP
®
surge current capability, when directly connected to the generator, will be found for the
ITU-T K.21 waveform at 310 µs on the surge graph and not 700 µs. Some common short circuit equivalents are tabulated below:
Standard
Open Circuit Voltage Short Circuit Current
ITU-T K.21
1.5 kV, 10/700
µs
37.5 A, 5/310
µs
ITU-T K.20
1 kV, 10/700
µs
25 A, 5/310
µs
IEC 61000-4-5, combination wave generator
1.0 kV, 1.2/50
µs
500 A, 8/20
µs
Telcordia GR-1089-CORE
1.0 kV, 10/1000
µs
100 A, 10/1000
µs
Telcordia GR-1089-CORE
2.5 kV, 2/10
µs
500 A, 2/10
µs
FCC Part 68, Type A
1.5 kV, <10/>160
µs
200 A,<10/>160
µs
FCC Part 68,Type A
800 V, <10/>560
µs
100 A,<10/>160
µs
FCC Part 68, Type B
1.5 kV, 9/720
µs
37.5 A, 5/320
µs
Any series resistance in the protected equipment will reduce the peak circuit current to less than the generators’ short circuit value.
A 1 kV open circuit voltage, 100 A short circuit current generator has an effective output impedance of 10
Ω
(1000/100). If the
equipment has a series resistance of 25
Ω,
then the surge current requirement of the TISP
®
device becomes 29 A (1000/35) and not
100 A.
MARCH 1994 - REVISED MARCH 2006
Specifications are subject to change without notice.
Customers should verify actual device performance in their specific applications.
BOURNS [ BOURNS ELECTRONIC SOLUTIONS ]
