RE: In-rush current specification (?)

["Ingraham, Andrew" <Andrew.Ingraham@compaq.com>]

>Is there a maximum in-rush energy limit for devices hot-plugged into PCI
expansion 
>cards?

For hot-plugging anything into a PCI expansion card, you're on your own, or
you default to the sub-adapter bus's specification.  There are no PCI
specifications I know of that govern sub-adapter cards that plug into a PCI
adapter card.

For hot-plugging PCI expansion cards themselves into a hot-plug capable
system, there is a maximum decoupling capacitance specification for the PCI
card.  That, coupled with the maximum supply voltage slew rate (dv/dt) limit
allowed for systems, would limit the inrush current on the card, due to
charging the capacitance, to no more than 9.9A in any system/card
combination.  The peak current might be more, because the operating current
(not into the decoupling capacitance) is on top of this.

>Is the Power Supply Rail Tolerance of 500 mA for the 12 V rail a "Maximum"
current? 
 
That is the operating current limit, "defined as current drawn by all loads
other than the decoupling capacitors."  See section 3.3 in the Hot-Plug
spec.  The instantaneous power-up current, when the Hot-Plug controller
powers up the PCI expansion card, might be more.

If you are hot-plugging something else into the PCI expansion card when the
latter is already up and running, that might qualify as part of its
operating current, subject to the 500 mA limit, because it can occur at any
time after the PCI card has already been powered up, and it is acceptable
for a system to limit the current to much less than 9.9 Amps.  The Hot-Plug
spec does say that "Adapter Cards ... that have a dynamic or switching load
must guarantee that the peak operating loads never exceed" that limit.