PCI Express* Add-in Card Considerations
24 613768
Figure 3-2: Duty Cycle Definition
Table 3-4: Duty Cycle Example Test Criteria for a 1000W PSU – RMS
Duty Cycle
Time for Power
Excursion (T
E
)
Time Constant
(T
C
)
Power @
T
E
Power
@ T
C
5% 1900 µs 100 µs 918 W 2000 W
8% 11.5 ms 1 ms 897 W 1800 W
12.5% 70 ms 10 ms 882 W 1600 W
25% 300 ms 100 ms 924 W 1200 W
NOTES:
The Capacitve Load mentioned in Table 4-6 is expected to be applied to this test
scenario.
Total Test time for each Power Excursion testing time is expected to last until thermal
saturation occurs in the PSU.
More details about test time for each row above and formulas to calculate T
C
and T
E
power values for different PSU sizes will be detailed in the “Desktop Platform Form
Factor Power Supply Test Plan – Doc #
338448
This Table is only applicable if a power supply does not provide the I_PSU% signal. As
I_PSU% is required for ATX12VO power supplies refer to Section
4.3.7, see Table 4-13
or Table 4-14 for an updated table.
3.2 PCIe* AIC Auxiliary Power Connectors
The PCIe* CEM 5.0 specification defines three 12V Auxiliary Power Connectors to be
used with PCIe* Add-in Cards
1. 75 W 2x3 connector
2. 150 W 2x4 connector
3. 600 W 2x6 12VHPWR connector (new in PCIe* 5.0)
Section 5.2
specifies the Mechanical information for all 12-volt Connectors. Note that
the Voltage Tolerance listed below is different from this Power Supply Design Guide for
the Low voltage tolerance
Table 4-2, the reason for the difference is allowing for
voltage drop on a motherboard from the Main Power Connector to the motherboard to
the PCIe* Edge Card Connector.
Table 3-5 shows the voltage tolerance required to
the PCIe* Add-in Card at both the motherboard edge card connector and Auxiliary
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