Power Considerations
8.2Power Sequencing
When either P_VIO or S_VIO is connected to a power supply other than VCCP, you must perform one of the following steps (listed in order from most favorably recommended to least favorably recommended):
1.Ensure that the P_VIO or S_VIO power comes up before or simultaneously with VCCP, and ensure that the P_VIO or S_VIO power goes down after or simultaneously with VCCP.
2.Alternatively, when the recommendation in item 1 is not followed, install a Schottky diode, as
shown in Figure 20, between VCCP and the VIO pin(s) (as appropriate). The diode must be sized appropriately for the power environment of the system.
3.Alternatively, when the recommendations in item 1 and item 2 are not followed, connect a
25 Ω
Ω
must never be at a voltage lower thanVCCP except in the case of a 25
Figure 20.
VCP | VIO |
Intel® 31154
133 MHz PCI Bridge
§ §
58 | Intel® 31154 133 MHz PCI Bridge Design Guide Design Guide |