TISP5070H3BJ, TISP5080H3BJ, TISP5110H3BJ, TISP5150H3BJ
FORWARD-CONDUCTING
UNIDIRECTIONAL THYRISTOR OVERVOLTAGE PROTECTORS
JANUARY 1998 - REVISED MARCH 1999
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, VD, values of -1 V,
-2 V and -50 V. The TISP5150H3BJ is also given for a bias of -100 V. Values for other voltages may be
determined from 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 Figure 12, 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. For example, the TISP5070H3BJ
has a differential capacitance value of 166 pF under these conditions.
normal system voltage levels
The protector should not clip or limit the voltages that occur in normal system operation. 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 TISP5150H3BJ, with a VDRM of -120 V, can be used to
protect ISDN feed voltages having maximum values of -99 V, -110 V and -115 V (range 3 through to range 5).
These three range voltages represent 0.83 (99/120), 0.92 (110/120) and 0.96 (115/120) of the -120 V
TISP5150H3BJ VDRM. Figure 9 shows that the VDRM will have decreased to 0.944 of its 25 °C value at
-40 °C. Thus the supply feed voltages of -99 V (0.83) and -110 V (0.92) will not be clipped at temperatures
down to -40 °C. The -115 V (0.96) feed supply may be clipped if the ambient temperature falls below -21 °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 m3 (1 ft3)
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.
P R O D U C T
I N F O R M A T I O N
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