Intel ATX12V - Manual (Page 32)

ATX12V Power Supply Design Guide
Version 2.0
32
The ATX Specification offers two options for venting between the power supply and the
system interior:
• The venting shown in Figure 8 provides the most effective channeled airflow for the
power supply itself, with little regard for directly cooling any system components. This
venting method is nearly always used in conjunction with a fan that exhausts out the
rear of the power supply.
• The venting shown in Figure 9 allows designers to more directly couple the power
supply airflow to system components such as the processor or motherboard core,
potentially cooling all critical components with a single fan. Both the power supply fan
location and direction may vary in this case. The trade-off is usually one of reduced
system cost versus narrower design applicability.
4.4. AC Connector
The AC input receptacle should be an IEC 320 type or equivalent. In lieu of a dedicated
switch, the IEC 320 receptacle may be considered the mains disconnect.
4.5. DC Connectors
Figure 10 shows pinouts and profiles for typical ATX power supply DC harness
connectors.
Listed or recognized component appliance wiring material (AVLV2), CN, rated min 85 °C,
300 VDC shall be used for all output wiring.
There are no specific requirements for output wire harness lengths, as these are largely a
function of the intended end-use chassis, motherboard, and peripherals. Ideally, wires
should be short to minimize electrical/airflow impedance and simplify manufacturing, yet
they should be long enough to make all necessary connections without any wire tension
(which can cause disconnections during shipping and handling). Recommended minimum
harness lengths for general-use power supplies are 280 mm for the +12 V power connector
and 250 mm for all other wire harnesses. Measurements are made from the exit port of the
power supply case to the wire side of the first connector on the harness.
NOTE
Details of the 2x3 “Optional Power Connector” mentioned in the ATX 2.03 Specification
are omitted from this design guide until such time as the signals on that connector are more
rigidly defined.