ATX Version 3.0 Multi Rail Desktop Platform Power Supply
Reliability – PS_ON# toggle for S0ix mode - REQUIRED
In order to optimize desktop platform power consumption, Intel provides design recommendation to enable PSU PS_ON# toggle on/off during S0 idle power mode (S0ix) to save both system and PSU power. The PSU PS_ON# may toggle on/off every 180s (PSU to be on for 1s and off for 180s) when customer desktop designs implement S0 idle which is different from the legacy desktop platform design that PS_ON# only toggle once when turn on. The S0ix mode is used in systems that use Alternative Low Power Modes.
If the computer turns on/off every 180 seconds the worse case scenario would be 480 times in one day and 175,200 times in one year. The power supply needs to be able to handle these many cycles for the life of the power supply.
To have better user’s experience and avoid PSU fan acoustic noise annoyance, system and PSU designers shall have at least two seconds delay time for the PSU fan to spin up after PS_ON# assertion. PSU is expected to support running at full load without any electrical, thermal components (i.e., IC, MOSFET, diode, transformer, inductor, capacitor, relay, fan, etc.) damaged or degradations during the period of time before the warranty expired. Due to the frequent PS_ON# toggle on/off, system and PSU component’s reliability should be considered based on the days, months, or years of claimed warranty listed on product specification. This is also mentioned in Section 5.3.2.