CME136686LX Hardware Manual - RTD Embedded Technologies ...

AT vs. ATX Power Supplies
Both AT and ATX power supplies may be used with the CME136686LX cpuModule, however AT power supplies
do not provide any standby power to the cpuModule. When an AT power supply is used to power the system,
low power modes that require a standby power to wake the system will not be fully supported.
ATX power supplies do provide a standby power, thus allowing the system to utilize all low power modes
supported by the hardware. When an ATX supply is used to power the cpuModule, lower power modes can be
achieved. During these low power modes, the standby power from the ATX power supply provides power to a
small circuit on the CPU, which is used to watch for a system wake event.
ATX Power Supply Signals
The auxiliary power connector (CN3) provides two ATX style signals., +5V Standby and PSON#. The +5V
Standby rail is used to power certain parts of the cpuModule when the main power supply is turned off, i.e.
during Suspend-to-RAM (S3), Hibernate (S4), or Soft-Off (S5) power modes. The PSON# signal is an active low
open-drain output that signals the power supply to turn on. Use of these signals allows the power consumption
to drop to below 1W during standby modes, and still enable any of the wake events.
BDM-610000065 Rev C Chapter 4: Using the cpuModule 81