MIL-STD-217F Ver la hoja de datos (PDF) - Sensitron
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MIL-STD-217F Datasheet PDF : 11 Pages
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SENSITRON
SEMICONDUCTOR
TECHNICAL DATA
DATASHEET 4310, Rev B
SPDXXD28 SERIES
Figure 8 – Low Side Switch, Negative Supply
Rise Time & Fall Time
The rise and fall times of the SPDXXD28 is pre-set at the factory for a nominal 100uS with a LINE supply of
28VDC (see Table 2 for min/max limits). The rise and fall times will vary linearly with supply voltage. The
PWRGND pin is used to control the rise and fall times. If the PWRGND pin is left open, the rise and fall times
will be about 50uS. Leaving the PWRGND pin open can be useful when a faster rise or fall time is desirable.
With the PWRGND pin connected as in Figures 5 through 8, the SPDXXD28 can turn on into a capacitive load
of 440uF, min, 880uF, typ, without tripping for any power supply voltage within the ratings.
Wiring and Load Inductance
Wiring inductance can cause voltage transients when the SPDXXD28 is switched off due to an overload.
Generally, these transients are small but must be considered when long wires are used on either the LINE or
LOAD pins or both. A 10 foot length of wire in free air will cause a transient voltage of about 10 Volts when the
SPD25D28 trips at an Instant Trip level of 250 Amps. At the rated load current of 25 Amps, the voltage transient
will be about 1 Volt. If longer wire lengths are used, a transient suppressor may be used at the LINE pin and a
power diode may be used at the LOAD pin so that the total voltage between the LINE and LOAD pins is less
than 50 Volts.
When powering inductive loads, the negative voltage transient at the LOAD pin can cause the voltage between
LINE and LOAD to exceed the SPDXXD28 rating of 50 Volts and a power diode from the LOAD pin to ground
must be used. The cathode of the power diode is connected to the LOAD pin with the anode connected to
ground. The power diode must be able to carry the load current when the SPDXXD28 switches off.
Paralleling
For example, putting two SPD25D28s in parallel will not double the rating to 50 Amps. Due to differences in the
Rds(on) of the Power Mosfets in the SSPCs, the current will not share equally. In addition, there are unit-to-unit
differences in the trip curves so that two SPD25D28s in parallel may possibly trip at 35 Amps. Also, both
SPD25D28s will not trip together; the SPD25D28 carrying the higher current will trip first followed by the other
SPD25D28. Multiple SPD25D28s may be used in parallel as long as these complexities are appreciated.
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