Advantech SOM-ETX Design Guide
power-on reset based on an internal monitor on the +5V input voltage and/or the
internal power supplies.
5.14.7 ATX Power Supply Control
PS-ON#
VCCSB5V
Power Button
ATX Power
0.1uF
SOM-ETX
PWRBTN#
Pin14
Pin9
Carryboard
PWRBTN pull-up resister is
already on SOM-ETX modules
Figure 5-47 ATX Power Supply Connections
Most SOM-ETX modules provide support for ATX-style power supplies in which the
main power output of the supply is controlled by the SOM-ETX module. The power
supply must provide a constantly present source of 5V power to support this
functionality.
Typical current consumption from the VCCSB5V supply pin is under 10mA.
The PS-ON# signal is an active-low output that turns on the main outputs of the
supply.
The PWRBTN# signal is used for a momentary contact, active-low input. The other
terminal of the pushbutton should be grounded. Asserting PWRBTN# indicates that
the operator wants to turn the power on or off. The system response to this signal
can vary among SOM-ETX modules and can be subject to modification by BIOS
settings or system software.
If an ATX power supply is not used, the SOM-ETX module’s PS-ON#, VCCSB5V,
and PWRBTN# pins should be left unconnected.
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Chapter 5 Carrier Board Design Guidelines
