Intel ATX12V manual Output Transient Response, Capacitive Load, DC Output Transient Step Sizes

ATX12V Power Supply Design Guide

Version 2.0

3.2.7. Output Transient Response

Table 11 summarizes the expected output transient step sizes for each output. The transient load slew rate is = 1.0 A/µs.

Table 11. DC Output Transient Step Sizes

	Max. step size	Max. step size
Output	(% of rated output amps per Sec 3.2.3) (1)	(amps)
+12 V1DC	40%
+12 V2DC	60%
+5 VDC	30%
+3.3 VDC	30%
-12 VDC		0.1 A
+5 VSB		0.1 A

(1)For example, for a rated +5 VDC output of 18 A, the transient step would be 30% × 18 A = 5.4 A

Output voltages should remain within the regulation limits of Section 3.2.1, and the power supply should be stable when subjected to load transients per Table 11 from any steady state load, including any or all of the following conditions:

•Simultaneous load steps on the +12 VDC, +5 VDC, and +3.3 VDC outputs (all steps occurring in the same direction)

•Load-changing repetition rate of 50 Hz to 10 kHz

•AC input range per Section 3.1

•Capacitive loading per Table 12.

3.2.8. Capacitive Load

The power supply should be able to power up and operate normally with the following capacitances simultaneously present on the DC outputs. This capacitive loading should be used to check stability and should not be included for noise testing.

Table 12. Output Capacitive Loads

Output	ATX12V
	Capacitive load (PF)
+12 V1DC	5,000
+12 V2DC	3,000
+5 VDC	6,000
+3.3 VDC	6,000
-12 VDC	350
+5 VSB	350

21