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SPECIAL FEATURE Paralleling power supplies requires that the output current of each power supply’s voltage rail be balanced. This is a task accomplished by a SHARE reference signal. An analog reference signal for each of the voltage rails is connected between each of the system power supplies through the appropriate SHARE pin. VITA 62 compliant solutions The first implementations of VITA 62 compliant solutions are now appearing on the market. An example is shown in Figure 3, the Dawn PSC-6236 Universal AC Input VITA 62 3U Power Supply for air or conduction cooled systems. Designed for mission critical applications, it delivers up to 400 Watts of output power over a wide temperature range. New products like this represent a standardized power supply ready to deliver in harsh mission critical environments. VME, VPX & VXS ONLINE A short summary of the benefits includes: and maintainability. Brian Roberts has 22 years of design experience in Silicon Valley developing electronic products for commercial and defense applications. Over this period, he has worked with clients in the areas of system engineering, power supply design, and other printed circuit board based solutions. Brian has been with the team at Dawn VME Products since 2005. Dawn VME Products 510-657-4444 www.dawnvme.com Explore... www.eecatalog.com/vme ➔ Directory of leading VME, VPX & VXS Solution Providers ➔ Top Stories and News ➔ White Papers ➔ Expert Opinions (Blogs) ➔ Exclusive Videos ➔ Valuable Articles ➔ Ask the Experts Sign up for the quarterly VME, VPX & VXS E-Product Alert 20 Engineers’ Guide to VME, VPX & VXS 2013
Tackling the Challenge of Building Smaller, Lighter, and More Efficient Componentbased Avionics with CFD Component thermal issues have to be managed in order to maintain high reliability in military aircraft and avionics environments. The ratio and tradeoff of size, weight, and power (SWaP) is a crucial system design consideration in modern defense systems. As aircraft are fitted with an increasing amount of electronics and with more components, they become heavier—and more weight can mean less time in the target zone. But they also become hotter as size density increases. The thermal behavior can also vary from component vendor to vendor but also over the component aging process. This is due to the degradation of the materials used in the component and the influence of thermal management over the lifetime of the component. A good understanding of semiconductor components’ thermal behavior is important because it is crucial to the optimum thermal design for a low SWaP ratio. Insufficient understanding of a component can lead not only to an oversized cooling system but also to a bad choice of the selected components intended for the lifetime system use. Thermal Characterization of Semiconductor Components A good way to begin formal component characterization is to create a “smart” implementation of the static test version of the Joint Electron Devices Engineering Council (JEDEC) JESD51-1 electrical test method [1] that allows for continuous measurement during a heating or cooling transient. The characterization method uses the temperature sensitivity of the semiconductor component. This sensitivity has to be measured before the actual characterization can begin, and it should be done according to the JESD51-14 standard to record the cooling curve of the component. Once the measured temperature sensitivity parameters (TSP) are obtained, the component can be characterized by powering up the device (heating it) with PH [Watt] until a steady state is reached. Once the junction temperature TJ is constant, the heating current is switched off to a lower measuring current that creates a low SPECIAL FEATURE Computational Fluid Dynamics software helps defense systems designers doubly: it aids in optimizing component SWaP, and models device thermal behavior across time and vendors. By Boris Marovic, Product Marketing Manager, Mentor Graphics Figure 1: Cooling curve of a sample component. measuring power PM [Watt]. The measuring current is negligible compared to the heating current. This sharp power step introduces the cooling process and is recorded until a steady state is reached. From the temperature sensitivity of the component and the lower steady state temperature, ideally realized with a cold plate, the transient cooling curve is created as shown in Figure 1. The temperature difference ΔT (Kelvin) is derived by the temperature sensitivity of the component; and the thermal resistance of the component can be calculated as shown in the equation: Rth = ΔT/(PH ‒ PM). From the recorded cooling curve, a structure function can be derived as shown in Figure 2. This structure function shows thermal resistance and capacitance of the single component layers from junction to environment. The vertical sections of the curve show [K/W] materials such as metallic layers in the component structure; whereas horizontal lines show higher thermal resistance layers such as die attach, glue, grease, and other thermal interface materials (TIM), PCB layers, and so on. www.eecatalog.com/vme 21
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Page 3 and 4: TAKE T TAKE YOUR YO YOUR R VIRTUAL
Page 5 and 6: The only compact, rugged chassis of
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Page 10 and 11: SPECIAL FEATURE We are also in the
Page 14 and 15: Advertorial 3U VPX Solutions from E
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Page 19 and 20: Table 1: Notional VITA 65 Channel G
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Page 31 and 32: intended message. To get past those
Page 33 and 34: Test and Analysis Teledyne LeCroy
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Page 41 and 42: Enclosures “Mupac” 760 Small Fo
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