MIL-DTL-23659F
APPENDIX A
A.7.6.5. Maximum No Damage Current (MNDC). The intent of this test is to establish the
lowest level electrical input which that could result in damage of the ILI. This level would be
used in evaluating inadvertent RF damage susceptibility at the system level. As a check to insure
that a potential safety hazard involving the inadvertent activation of an energetic material
reaction within the initiator is not over looked, a minimum threshold must be exceeded by the
mean MNDC. This threshold value has been established based on past safety critical Electro-
explosive Device (EED) no-fire requirements and is believed not to create a technical challenge
within the existing state of the art for ILI. This requirement is based on the assumption that the
current level that is capable of damaging the ILI is lower than the current level required to cause
a reaction of the energetic material within the ILI. If the analysis of MNDC results do not met
the 1 Amp requirement, the developer is to consult the cognizant safety authority for direction.
A.7.6.6. Electrostatic Discharge. This test confirms minimum acceptable design safety and
reliability characteristics of the ILI with respect to inadvertent ESD inputs. There are two ways
an ILI can be damage by ESD, each case could influence device reliability and safety. The first
way is when the damage occurs by a breakdown of the ILI insulation when potential is
developed between the pin and case of the ILI. The pin to case test with the 5000 ohm resistor in
series with the ILI may be more severe than when the 500 ohm is in series because the longer
pulse duration may increase the probability of a breakdown even though less current is
developed. Therefore, pin-to-case tests with each resistor in series with the ILI are required.
The second way is when the bridge is heated by potential between the pins of the ILI. The
energy delivered through a 500 ohm resistor to the ILI is greater than that delivered through a
5000 ohm resistor. If the device passes the test with a 500 ohm resistor, it will also pass with a
5000 ohm resistor. Therefore, pin-to-pin tests with the 500 ohm resistor only in series with the
ILI are required. It is unlikely to expect any damage, much less a reaction in the pin-to-pin mode
for ILI. Simple calculation shows that the maximum current into a detonator from a capacitor
charged to 25,000 volts through a 500 ohm resistor is 50 amps, or almost 2 orders of magnitude
less than a typical ILI burst current. Since the RC time constant is around 0.25 microseconds
(500 pico Farads into 500 Ohms), the current drops off in a few hundred microseconds which is
more than sufficient time for bridge burst. The total energy in the capacitor is 156 millijoules.
For a typical bridge of 50 milliohm resistance, only 1/10,000 of the energy is deposited in the
bridge because the 500 ohm resistor in series absorbs most of the energy. Thus, the total energy
that can ever be deposited in the bridge is on the order of 16 microjoules. The calculated energy
deposited in the bridge (bridge resistance divided by total circuit resistance) is at least a factor of
10 less than the short pulse no fire energy. Over time, as ILI are tested pin-to-pin without
damage, the pin-to-pin testing requirement may be eliminated, once enough confidence is
developed that ILI are immune pin to pin ESD.
A.7.6.7. High Firing Voltage. It may not be true that all ILI are more reliable as the input
firing voltage is increased. The objective of the test is to determine if the ILI is reliable at firing
potentials that significantly exceed the system's intended firing voltage. This test is to provide
the developing agency information about the chosen ILI in terms of design margin over the
expected application firing voltage.
A.7.6.8. Environmental Tests. The required test levels for temperature, shock, vibration, etc.
are based on the levels that will cover most applications, but they do not cover the most severe
environments ILI can be exposed to. For example, ILI in tandem warheads, penetrating
weapons, or artillery should have vibration or shock environmental tests that exceed those
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