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Intel ATX Power Supply Design Guide
Version 0.9
Page 29
7. Reliability
7.1 Component Derating
The following component derating guidelines shall be followed:
• Semiconductor junction temperatures shall not exceed 110 °C with an ambient of
50 °C. Any exceptions are subject to final approval.
• Inductor case temperature shall not exceed safety agency requirements.
• Capacitor case temperature shall not exceed 95% of rated temperature.
• Resistor wattage derating shall be > 30%.
• Component voltage and current derating shall be > 10% at 50 °C. Any exceptions are
subject to final approval.
• Magnetic saturation of any transformer will not be allowed under any line, load, startup,
or transient condition including 100% transients on the five main outputs or +5VSB.
7.2 Mean Time Between Failures (MTBF)
The MTBF of the power supply shall be calculated utilizing the Part-Stress Analysis
method of MIL-HDBK-217F using the quality factors listed in MIL-HDBK-217F. The
calculated MTBF of the power supply shall be greater than 100,000 hours under the
following conditions:
• Full rated load
• 120 VAC input
• Ground benign
• 25 °C ambient.
The calculated MTBF of the power supply shall be greater than 30,000 hours under the
following conditions:
• Full rated load
• 120 VAC input
• Ground benign
• 50 °C ambient.