Intel ATX12V - Closed-Loop Stability; VDC; +3.3 VDC Power Sequencing; Voltage Hold-Up Time; Timing; Housekeeping; Control

ATX12V Power Supply Design Guide
Version 2.0
22
3.2.9. Closed-loop Stability
The power supply shall be unconditionally stable under all line/load/transient load
conditions including capacitive loads specified in Section 3.2.8. A minimum of 45 degrees
phase margin and 10 dB gain margin is recommended at both the maximum and minimum
loads.
3.2.10. +5 VDC / +3.3 VDC Power Sequencing
The +12 VDC and +5 VDC output levels must be equal to or greater than the +3.3 VDC
output at all times during power-up and normal operation. The time between the +12 VDC
or +5 VDC output reaching its minimum in-regulation level and +3.3 VDC reaching its
minimum in-regulation level must be ≤ 20 ms.
3.2.11. Voltage Hold-up Time
The power supply should maintain output regulation per Section 3.2.1 despite a loss of
input power at the low-end nominal range—115 VAC / 57 Hz or 230 VAC / 47 Hz—at
maximum continuous output load as applicable for a minimum of 17 ms.
3.3. Timing / Housekeeping / Control
PS_ON#
PWR_OK
PWR_OK Sense Level = 95% of nominal
95%
10%
~
~
~
T2
T3
T4
T6
timing_3_5_12b
+12VDC
+5VDC
+3.3VDC
O/P's
}
VAC
~
T5T1
Figure 6. Power Supply Timing
Notes: T1 is defined in Section 3.3.4. T2 is defined in Section 3.3.5. T3, T4, T5, and T6 are defined in Table 13