ATX Version 3.0 Multi Rail Desktop Platform Power Supply
Design Guide
Power-On Time – REQUIRED
The power-on time is defined as the time from when PS_ON# is pulled low to when the +12 VDC, +5 VDC, and +3.3 VDC outputs are within the regulation ranges specified in Table 4-2. The power-on time shall be less than 500 ms (T1 < 500 ms).
+5VSB shall have a power-on time of two second maximum after application of valid AC voltages as shown in Figure 4-5. The 5VSB power on time is T0 as listed in Section Section 4.3.4.