The conga-XLX provides support for controlling ATX-style power supplies. In order to do
this the power supply must provide a constant source of 5V power. When not using an
ATX power supply then the conga-XLX's pins PS_ON, 5V_SB, and PWRBTN# should
be left unconnected.
PS_ON#
The PS_ON (pin 5 on the X4 connector) signal is an active-low output that turns on the
main outputs of an ATX-style power supply. This open-collector signal can be pulled up
to the 5V_SB supply voltage through the use of a 1K resistor. Usually there is a pull-up
resistor internally implemented in the power supply itself yet it is also good practice to
implement a footprint for the pull-up resistor in the baseboard circuitry.
PWRBTN#
When using ATX-style power supplies PWRBTN# (pin 7 on the X4 connector) is used to
connect to a momentary-contact, active-low pushbutton input while the other terminal on
the pushbutton must be connected to ground. This signal is XTX
™
internally pulled up to
5V_SB using a 4k7 resistor. When PWRBTN# is asserted it indicates that an operator
wants to turn the power on or off. The response to this signal from the system may vary
as a result of modifications made in BIOS settings or by system software.
Power Supply Implementation Guidelines
5 volt input power is the sole operational power source for the conga-XLX. The
remaining necessary voltages are internally generated on the module using onboard
power supplies. A baseboard designer should be aware of the following important
information when designing a power supply for a conga-XLX application:
•
As mentioned earlier in section 4.1.4 the conga-XLX is capable of generating an
onboard 3.3V supply with an output current that is limited to 500mA. If an external
device requires more then this 500mA limit then it's necessary to design a 3.3V
supply into the baseboard.
Caution
It is not possible to connect an external 3.3V supply to the onboard generate 3.3V
supply pins on the conga-XLX module. This will cause a current cross-flow and may
result in either a system malfunction and/or damage to the external power supply and
the module.
•
Sometimes when designing baseboards, baseboard designers choose to fuse power
to some external devices such as keyboards or USB devices by using solid-state or
polyswitch overcurrent protection devices. This results in the protective devices
typically only opening after they pass several times their rated current for long
periods of time. When the application power supply is incapable of generating the
necessary current needed to open these protective devices it's possible that the
application crashes as a result of an external fault and therefore will reduce the
applications reliability as well as make a fault diagnosis of the application difficult.
•
It has also been noticed that on some occasions problems occur when using a 5V
power supply that produces non monotonic voltage when powered up. The problem
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