Intel ATX 0.9 - Manual (Page 15)

Intel ATX Power Supply Design Guide
Version 0.9
Page 15
3.3.7 +5VDC/+3.3VDC Power Sequencing
The +5VDC output level must be equal to or greater than the +3.3VDC output at all times
during power-up and normal operation. The time between the +5VDC output reaching its
minimum in-regulation level and +3.3VDC reaching its minimum in-regulation level must
be less than or equal to 20 ms.
3.3.8 Voltage Hold-up Time
The power supply shall maintain output regulation per Section 3.2.1 despite a loss of input
power at the low-end nominal range (Low = 115 VAC, 57 Hz or 230 VAC, 47 Hz) at
maximum continuous output load as applicable for a minimum of 17 ms.