EKF SC3-LARGO - Main Power Supply Control (PS_ON#); Power Supply Status (PWR

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User Guide • SC3-LARGO • CompactPCI

Serial CPU Board • Intel

Core

5xxx Processor

Main Power Supply Control (PS_ON#)

The SC3-LARGO draws its power from the +12V main supply rail defined by the CompactPCI

Serial

specification. The board has been designed to control this main power supply by use of the signal

PS_ON# (connector P1 pin E2). If the system enters the sleep state S5 (soft off), the signal PS_ON#

is pulled high, hence the main power supply is switched-off. The SC3-LARGO is held in soft off state

until a power management event (e.g. power button event triggered by the front panel handle) brings

back the system to the S0 state.

In order to work as described above and to generate clean signals on PS_ON#, the stand-by voltage

+5VSTB is necessary. This optional power rail, tied to connector P1 pin B1, is also part of the

CompactPCI

Serial specification. The stand-by power rail must be switched-on “always”, independent

of the state of PS_ON#.

Nevertheless, +5VSTB is not mandatory to operate the SC3-LARGO. If no stand-by power is available,

the board creates this voltage from the main power rail. In this case it is important that the PS_ON#

signal is pulled down somewhere in the system.

Power Supply Status (PWR_FAIL#)

Power supply failures may be detected before the system crashes down by monitoring the signal

PWR_FAIL#. This active low line (connector P1 pin F3) is an addition to the CompactPCI

Serial

specification and may be driven by the power supply. PWR_FAIL# signals the possible failure of the

main supply voltage +12V. On the SC3-LARGO the signal PWR_FAIL# is routed to GPIO4 of the

QM87 PCH to analyse the state of the power supply unit.

EKF SC3-LARGO - Main Power Supply Control (PS_ON#); Power Supply Status (PWR_FAIL#)