TISP4165H4BJ THRU TISP4200H4BJ, TISP4265H4BJ THRU TISP4360H4BJ
BIDIRECTIONAL THYRISTOR OVERVOLTAGE PROTECTORS
NOVEMBER 1997 - REVISED MARCH 1999
a.c. power testing
The protector can withstand 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).
capacitance
The protector characteristic off-state capacitance values are given for d.c. bias voltage, V
D
, 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 V
D
= 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, such as Figure 15 and Figure 17, 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.
normal system voltage levels
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.
DRM
value at temperatures below 25 °C. The calculated
value should not be less than the maximum normal system voltages. The TISP4265H4BJ, with a V
DRM
of
200 V, can be used for the protection of ring generators producing 100 V rms of ring on a battery voltage of
-58 V (Th2 and Th3 in Figure 17). The peak ring voltage will be 58 + 1.414*100 = 199.4 V. However, this is the
open circuit voltage and the connection of the line and its equipment will reduce the peak voltage. In the
extreme case of an unconnected line, clipping the peak voltage to 190 V should not activate the ring trip. This
level of clipping would occur at the temperature when the V
DRM
has reduced to 190/200 = 0.95 of its 25 °C
value. Figure 10 shows that this condition will occur at an ambient temperature of -22 °C. In this example, the
TISP4265H4BJ will allow normal equipment operation provided that the minimum expected ambient
temperature does not fall below -22 °C.
JESD51 thermal measurement method
To standardise thermal measurements, the EIA (Electronic Industries Alliance) has created the JESD51
standard. Part 2 of the standard (JESD51-2, 1995) describes the test environment. This is a 0.0283 m
3
(1 ft
3
)
cube which contains the test PCB (Printed Circuit Board) horizontally mounted at the centre. Part 3 of the
standard (JESD51-3, 1996) defines two test PCBs for surface mount components; one for packages smaller
than 27 mm on a side and the other for packages up to 48 mm. The SMBJ measurements used the smaller
76.2 mm x 114.3 mm (3.0 “ x 4.5 “) PCB. The JESD51-3 PCBs are designed to have low effective thermal
conductivity (high thermal resistance) and represent a worse case condition. The PCBs used in the majority
of applications will achieve lower values of thermal resistance and so can dissipate higher power levels than
indicated by the JESD51 values.
PRODUCT
INFORMATION
9
POINN [ POWER INNOVATIONS LTD ]
