12V2 Capability Calculation Reference Equation

The 12V2 PSU rail voltage has a nominal voltage of 12 volts. The lowest acceptable voltage for this rail is 11.4 V which can include reduction from the wire’s loss and Motherboard power planes loss. Motherboard VR efficiency assumption is 85% at PL2 Power, 80% at PL4 Power, and PL4_​PSU Power (AKA IccMax) Motherboard plane resistance is 1.1 mΩ. If the power supply supports the 240VA Energy Hazard protection requirement, then Current levels for the 12 Volt rail above 18 Amps should be split into multiple 12V rails.

• 12V2 Peak Current = (PL4.app Power / VR efficiency) / 11.4 V
• 12V2 Continuous Current = (PL2 Power / VR efficiency) / 11.4 V
• The PL2 Power duration time as below equation:

PL2 duration time= -PL1tau×LN(1-(PL1/PL2))

• • Tau values can be found in the Platform EDS listed in the Intel’s Reference Documents for each processor.
    • PL1 tau is CPU thermal solution dependent.
    • Customers can size PSU by using the above equation only when CPU thermal PL1 tau is known.