Application Note: Lightning Protection For Aircraft Electrical Power And Data Communication Systems

Using The Microsemi 200KPxxxC TVS and Family of Suppressors

A jetliner is struck by lightning at least once every 1,000 flying hours while safely transporting passengers and crew to their destination. Within its thin metal and composite shell, tens of thousands of sensitive semiconductor chips are performing critical functions from navigation to jet engine controls. Each of these components must be protected to maintain safe, reliable performance. Every new jet aircraft design undergoes more than 1,000 simulated lightning zaps to determine the protection levels and suppressor placement required for its myriad power and signal lines.

Lightning-caused transient voltages are defined in the Aircraft Standard RTCA/DO-160D. Both voltage and current threat levels, along with their waveform types, are defined in Section 22, Tables 22-2 and 22-3 with peak pulse currents ranging from 4 A up through 5,000 A. Waveform durations range from a few microseconds up through 500 microseconds, illustrating the broad range of lightning threats to avionics equipment.

Transient voltage protection from lightning must be totally effective to prevent equipment failure from potentially damaging surges. Designers' first choice for optimum performance have been the silicon Transient Voltage Suppressor. TVS devices populate circuit boards extensively throughout aircraft systems. TVS devices across ac and dc power distribution lines must be compatible with short-term high-line voltage excursions produced by the power generators.

This Microsemi application note provides a thorough guide for the design engineer in determining the most effective TVS protection across power and signal line interfaces. It explains how to convert the power and current of the traditional 10/1000 µs waveform as specified for most TVS devices, or any other waveform, to those for aircraft protection requirements. Many examples will illustrate and assist TVS device selection for almost all aircraft lightning protection applications.