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Diode Selection Guide - Transient Voltage Suppression
RTCA DO-160, Environmental Conditions and Test Procedures for Airborne Equipment, is a widely used criterion for verifying the capability of equipment to withstand the effects of lightning induced electrical transients. In Section 22 of this standard, entitled Lightning Induced Transient Susceptibility, the test methods and procedures for performing pin injection and cable bundle testing on aircraft equipment are defined. In order to verify the capability of an electronic system to withstand the effect of lightning induced transients, test procedures define the lightning induced transient by two characteristics.
- The transient waveform which shows how quickly the transient is induced and how long it lasts. This is sometimes referred to as the pulse width and is measured in seconds. The pulse width is related to the level of damaging energy contained within the transient, i.e. the longer the pulse, the more damage it will cause. The three most commonly referenced pin injection lightning waveforms from RTCA/DO-160E, Section 22, are shown in the figures below.
- The test level which defines the magnitude of the pulse. This is related to the anticipated level of exposure of the electronic system, i.e. if a system is tucked away in a safe environment, e.g. inside a metal enclosure with the interconnecting wiring being well shielded, the test level will be low. However, if the system is highly exposed to the electromagnetic environment, the test level will be high. The test level is described in terms of the open circuit voltage (Voc) and the short circuit current (Isc).
In the table below for waveforms 3, 4, and 5A, we show the recommended diode clamping voltage (Vc) and power rating (Ppp) at each test level for these waveforms.
|Diode Clamping Voltage (Vc) Selection for Lighting Strike Waveform Threats|
|RTCA/DO-160||LEVEL 1 100V/4A||LEVEL 2 250V/10A||LEVEL 3 600V/24A||LEVEL 4 1600V/60A||LEVEL 5A 3200V/128A||Recommended TVS (Ppp) @10/1000μs|
|Waveform 3 1MHz Damped Sinusoidal Wave (Ref. Fig. 22-4 from DO-160E)||Vc ≤ 97 V||Vc ≤ 243 V||Vc ≤ 275 V||Vc ≤ 87 V||Vc ≤ 32.2 V||500 Watts|
|Vc ≤ 97 V||Vc ≤ 243 V||Vc ≤ 275 V||Vc ≤ 87 V||Vc ≤ 35.8 V||600 Watts|
|All||All||All||Vc ≤ 243 V||Vc ≤ 96.8 V||1,500 Watts|
|All||All||All||Vc ≤ 275 V||Vc ≤ 209 V||3,000 Watts|
|All||All||All||All||Vc ≤ 275 V||5,000 Watts|
|RTCA/DO-160||LEVEL 1 50V/10A||LEVEL 2 125V/25A||LEVEL 3 300V/60A||LEVEL 4 750V/150A||LEVEL 5A 1600V/320A||Recommended TVS (Ppp) @10/1000μs|
|Waveform 4 Double Exponential 6.4 X 69 μsec (Ref. Fig. 22-5 from DO-160E)||All||All||Vc ≤ 31.9 V||Vc ≤ 11.3 V||NONE||500 Watts|
|All||All||Vc ≤ 38.2 V||Vc ≤ 13.6 V||NONE||600 Watts|
|All||All||All||Vc ≤ 35.0 V||Vc ≤ 16.0 V||1,500 Watts|
|All||All||All||Vc ≤ 74.0 V||Vc ≤ 29.2 V||3,000 Watts|
|All||All||All||Vc ≤ 134 V||Vc ≤ 35.5 V||5,000 Watts|
|All||All||All||All||Vc ≤ 114 V||15,000 Watts|
|All||All||All||All||Vc ≤ 146 V||30,000 Watts|
|All||All||All||All||All||200,000 Watts @ 10/40us|
|RTCA/DO-160||LEVEL 1 50V/50A||LEVEL 2 125V/125A||LEVEL 3 300V/300A||LEVEL 4 750V/750A||LEVEL 5A 1600V/1600A||Recommended TVS (Ppp) @10/1000μs|
|Waveform 5A Double Exponential 40 X 120 μsec (Ref. Fig. 22-6 from DO-160E)||All||Vc ≤ 10 V Vc ≥ 114.9 V||NONE||NONE||NONE||500 Watts|
|All||Vc ≤ 12.4 V Vc ≥ 112.6 V||NONE||NONE||NONE||600 Watts|
|All||Vc ≤ 42.2 V Vc ≥ 82.8 V||Vc ≤ 12.1 V||None||NONE||1,500 Watts|
|All||All||Vc ≤ 25.5 V||Vc ≤ 9.4 V||NONE||3,000 Watts|
|All||All||Vc ≤ 45.8 V||Vc ≤ 15.9 V||NONE||5,000 Watts|
|All||All||All||Vc ≤ 49.9 V||NONE||15,000 Watts|
|All||All||All||Vc ≤ 77.4 V||NONE||30,000 Watts|
|All||All||All||Vc ≤ 231 V||NONE||200,000 Watts @ 10/40us|