Feature: Aerospace, Military & Defence


be prevented by monitoring the I/V curve. Tis helps catch any problems early, avoiding false failures during qualification. Another way to prevent qualification failures is by conducting


additional tests before sending a failed unit for analysis. One effective test is measuring contact resistance. Tis helps pinpoint the location and cause of the failure. High temperature operating life (HTOL) testing is another


critical phase where devices can fail. Properly determining thermal resistance (theta Jc) is vital to avoid overheating. Termal scans provide crucial insights, helping identify overheating areas and allowing corrective actions. Electrostatic discharge (ESD) can also lead to failures during


qualification. Including control units in testing alongside units undergoing ESD helps ensure adherence to ESD protocols, confirming proper handling during the process. Grouping pins based on function and applying ESD in separate


compartments reduces the risk of ESD failures. Additionally, for sophisticated devices like the Apollo MxFE, careful clock conditioning is essential, especially when using internal PLLs or clocks. Proper oscillator frequency and voltage levels are critical to ensure reliable testing. Addressing issues with crystal oscillator circuitry during


HTOL testing is important. Modifying the schematic and layout helps, but implementing these changes in the qualification board may entail significant costs. To avoid this, an adaptor board policy such as that adopted by ADI’s AD9084 can be a cost- effective solution.


Figure 7: Apollo MxFE HTOL board running successfully with the clock adapter board attached successfully to the HTOL board


Adhering to the guidelines outlined in this article can


effectively diminish the occurrence of qualification failures. It’s important to note that a significant portion of these failures is attributed to external factors rather than inherent issues with a component. However, by diligently following these steps, not only can the incidence of qualification setbacks be lowered but also a thorough analysis to pinpoint the root causes can be conducted. Tis streamlined approach aids in timely product release to the market, while also minimising the requirement for testers and man-hours. Additionally, it facilitates the identification of specific areas of concern, allowing for comprehensive feedback to be provided to the design team.


Figure 6: Optimised clock signal generated from the modified adaptor board going to each of the HTOL device under stress, eight of them without attenuation or clock jitter]


As depicted in the example of ADI’s Apollo MxFE shown in


Figure 6, each of the adaptor boards with the modified clocking scheme underwent individual verification. Te subsequent challenge was to affix these adaptor boards onto the existing HTOL boards, which had a flawed clocking scheme. Te specific solder points were identified, and the adaptor boards were successfully soldered onto the existing HTOL board. Tis adaptation worked seamlessly, resulting in substantial cost and


ADI is committed to delivering reliable, high-performance solutions and continually enhancing internal processes to achieve this goal. Since the qualification of the Apollo MxFE, additional qualification tests and processes have been introduced. Tese enhancements encompass various aspects, including current and voltage measurements for individual devices under stress (DUST). Comparators are also being used to monitor whether the voltage surpasses the target value, with LED indicators signalling the status. Furthermore, to bolster reliability, a watchdog timer controlled by a microcontroller has been incorporated to serve as a safeguard and shut the system down in the event of a power glitch, preventing any potential damage to the reliability units. Improvements such as these help to further ensure zero failures during the qualification of highly complex integrated circuits.


Analog Devices: www.analog.com www.electronicsworld.co.uk May 2025 35


time savings that would’ve been spent on redeveloping a new board. Following the optimisation of the clocking scheme and the completion of the qualification for the AD9084, no failures were observed during any HTOL tests undertaken to date.


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