The growing importance of state-of-the-art circuit protection in commercial avionics

12 December 2014

The avionics industry has become an important factor in the global economy and flying a natural part of modern life.

This can largely be attributed to the fact that commercial air travel is considered to be one of the safest and most reliable forms of transportation currently available. However, it is still important to remember that it never would have achieved this status without extremely complex electronics that enable nearly all functions on an airplane. 

The main areas of commercial avionics include communication networks and navigation, control systems, radar, surveillance and display systems. Advanced commercial avionics cover other areas, for instance steering systems, airplane sensors, landing aid systems, infotainment, advanced warning technology, upgraded cockpits with LED displays, sophisticated weather data collectors that detect severe turbulence or wind shear and flight recorders that analyse common problems. Today, regulators, pilots and airlines rely on advanced tracking and recording technologies to share extensive information about flying hazards and this, in turn, enhances the reliability and safety of commercial air travel. 

As the safety of commercial flight continues to progress, the demand for advanced commercial avionics technologies also continues to grow. For instance, Avascent recently projected that the global market for commercial avionics equipment will grow at a rate of 4.8% through 2019. Furthermore, the firm estimates that $21 billion will be spent on commercial avionics systems for fixed-wing commercial aircraft in 2015 alone. 

Passengers must be able to depend on all components, that are necessary to ensuring a safe flight, to function properly. At the same time, it is important to keep in mind that avionics systems are subjected to a variety of hazardous conditions, lightning and electrostatic discharges that produce extremely high voltages that can cause the sensitive networks on board to fail. Electrical systems located in hidden panels that are difficult to access by crew members can be damaged by overvoltage transients that render them useless or faulty. An avionics system failure can lead to expensive repairs or even require a replacement of the equipment. At worst, a failure can jeopardise the lives of crew members and passengers. 

TVS diodes for the best possible circuit protection 

Protecting the electronics is extremely important and explains why transient voltage suppression (TVS) diodes are being used more often. These suppresion diodes are designed in such a way that they can reliably absorb damaging transients for short periods of time and thus provide reliable protection for electronic equipment. 

Particularly in aviation electronics such as full authority digital engine control (FADEC) systems, airplane sensors, avionics computers, fly-by-wire flight control systems, cockpit electronic equipment and airport landing aid systems, TVS diodes protect electronic circuits against transients and overvoltage threats such as EFT (electrically fast transients) and ESD (electro-static discharge). These silicon avalanche devices are the products of choice due to their fast response time, low clamping voltage, high surge capability and low leakage current. 

Top features of optimal TVS diodes 

The upscreening and sorting process used to ensure that only the TVS diodes that meet all the rigorous test procedures of the MIL-STD and JEDEC standards are selected is clearly the most important feature. This highly precise process ensures exceptional reliability and performance of the devices. In addition to the screening and sorting, surge testing, high-temperature reverse bias (HTRB) testing and electrical test sorting should be available. 

For flexibility, the TVS diode should be produced using one of two options: 1. off-the-shelf upscreening and Group B test stresses, including surge immunity, burn-in (i.e. HTRB), etc. or 2. customised upscreening and sorting process flows dictated by the manufacturer’s internal requirements. Ideal TVS diodes come in compact SMB, SMC, and SMD DO-214AA packages and are rated between 600 and 3,000W of peak pulse power dissipation. They should also allow for easy design-in compliance with the RTCA/DO-160 Standard for Environmental Conditions and Test Procedures for Airborne Equipment. 

The growing demands for safety and reliability of the commercial avionics industry are resulting in higher demand for complex avionics. However, due to the fact that a breakdown in sensitive board networks can have catastrophic consequences, the demand for circuit protection technologies to protect the sensitive electrical components within these complex systems also continues to rise. 

Proper circuit protection that uses TVS diode technology ensures the safety and integrity of the aircraft electronics and protects the lives of the crew and passengers. Prescreened, presorted TVS diodes with a compact package deliver the most reliable protection and performance for commercial avionics. Design engineers should therefore partner with a reliable circuit protection manufacturer with specialised expertise in TVS diodes for critical applications, advanced testing services and a track record of use in the aerospace industry that ensures market-proven results. 

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