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I am looking at many tvs diode online, and I wanted to know how to calculate to check if it complies with DO-160 indirect lightning surge protection.

For DO-160, there are Waveform 3, 4, 5A&B, and each waveform has its own requirement. Can some please give me an example on how to check if the tvs diode complies with each waveform.

I am also worried about certain phrase such as pin injected, cable injected, and multiple burst, single burst. I don't know what is going on. Please help out.

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Please explain what is going on with the requirement and how to calculate as an example.

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The first thing to appreciate about the DO160, is it is a test procedure specification. When a system requirement states that an LRU is to be compliant to DO160F section 22 (ie the induced transient section), it is expecting a test procedure to be performed on the UUT which is compliant to DO 160.

The DO-160 outlines the waveforms (Waveform 4, 5a etc), the test levels (1600V, 1600A) and how the test is to be performed. Your system specification should inform you which waveform and the threat level the LRU shall be subjected to since this is dependant on the location within the airframe.

Pin injection and cable bundle are two related tests to validate the LRU is suitably designed to survive a representative environment. Pin injection is to ensure no damage is occurs under a threat scenario while a cable bundle test is to test for high EM disturbances during a strike event.

How to design for or validate what is chosen is suitable

A TVS has six key parameters

Ppp Peak Pulse Power. This is the power rating of the devices and should not be exceeded. Take care of temperature derating and design margin de-rating

Ipp Peak pulse current.

Vwm Working voltage. This is the voltage at which a TVS is guaranteed to to conduct more than the leakage

Vbr(min) This is the minimum voltage the TVS will start to avalaunch the test current

Vbr(max) This is the maximum voltage the TVS will start to avalaunch the test current

Vclamp(max) This is the maximum clamping voltage at the rated current.

Working voltage

Knowing the maximum voltage the LRU could be subjected to influences the Vwm of the device (or devices in series) needed.

Take the 115V bus. The transient worst-case voltage is 180Vrms for 100ms ( 16.5.2.3.1 ) and thus this sets your working voltage at 255V to chassis.

Source impedance

Knowing the voltage and the current of a waveform is required to understand the source impedance of the thread. Assume the 115V was to be subjected to 1000V/1000A, Waveform 5a. This has a source impedance of 1R. This is required to down-select the TVS's capable of handling such currents

Knowing the threat voltage, the minimum breakdown voltage and the source impedance, the peak threat current can be calculated

\$Ipk = \frac{ V_{oc} - \Sigma V_{br(min)}}{R_{source} + R_{circuit}}\$

This is a pessimistic maximum

Clamping voltage

With a pessamistic maximum current known, a representative clamping voltage can be calculate via linear interpolation between Vbr(min) at test current and Vclamp at max current.

TVS Power

With the conduction current and the blocking voltage known, the Peak pulse power can be calculated. This needs to be compared against the energy and the peak pulse power of the waveform.

How to determine the energy and the peak power of a double-exponential, or multi-stroke. There are a number of ways. One proven way is via the Wunsch-Bell relation where a "K-factor" which is dependent on the type of waveform, is used to approximate teh energy

https://www.microsemi.com/document-portal/doc_download/14639-micronote-120-selecting-tvs-with-ppp-and-waveform-considerations

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  • \$\begingroup\$ Lets say that the tvs diode short circuits and passes pin injection test. Does that mean it will survive cable injection as well? \$\endgroup\$
    – Kasap23
    Oct 27, 2019 at 20:23
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    \$\begingroup\$ From a TVS perspective, the pin injection is typically the harshest waveform. If the specifications are correct with regards to what shall be applied for injection, what shall be applied for bundle, then it should be fine. Do the maths, do the test, get the evidence, submit the DDP :) \$\endgroup\$
    – user16222
    Oct 27, 2019 at 20:42
  • \$\begingroup\$ I have done the pin injection calculation and found out that it complies with the DO-160 standard. There were examples of Pin injection calculation online. How do I calculate for the cable injection? Or how different is the cable injection calculation compared to pin injection calculation? \$\endgroup\$
    – Kasap23
    Oct 28, 2019 at 19:11
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    \$\begingroup\$ That's not what I said. I said the methodology is the same, just the means to calculate the energy is different. I am not sure how you came to the conclusion the calculation is the same. The steps you go through (the methodology) are the same but since the waveforms are different the means to calculate the energy must be different. Once you know the energy the steps are the same. \$\endgroup\$
    – user16222
    Oct 28, 2019 at 21:20
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    \$\begingroup\$ TVS's do not care about waveforms, they care care about voltage, current, power. As I said, the methodology is the same, the means to calculate the energy is different \$\endgroup\$
    – user16222
    Oct 28, 2019 at 23:57

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