Re: Adapter board 3.3V regulators

[Charles Curley ETW <ccurley@dwarf.fc.hp.com>]

-> -> 
-> -> Please tell me what the best way to generate 3.3V on my PCI Local bus
-> -> adapter card.
-> -> 
-> -> 
-> 
-> Charles curley writes ---
-> 
-> >Do you really need to? PCI Spec 2.1 requires 3.3V power rails even on a 5V
-> >signaling environment. See sec. 4.1.1.
-> 
-> >In my opinion, card designers should be designing universal cards.
->  
-> 
-> 
-> Systems implementing 5V signaling are _NOT_ required to provide 3.3v in their
-> system.  See Section 4.3.4.1.  
->     "System vendors are nonetheless encouraged to provide 3.3V power for
->      PCI slots....."
-> As a board designer, I'd love to see a guarantee of 3.3V from the system.
-> But it's not guaranteed....If you want 3.3V on your card in a 5V system, then
-> you'd better generate it yourself from 5V or from 12V.


I sit corrected. May I take my foot out of my mouth now? :-)

I believe this provides for a nice chicken & egg situation. We won't see
backplanes provding 3.3V power until we see a lot of Universal cards, or
even 5V cards with 3.3V components. We won't see a lot of Universal cards,
or even very many 5V cards with 3.3V components, unitl we have a lot of
backplanes with 3.3V power supplies.

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Charles Curley is not an employee of Hewlett Packard.

This message does not necessarily represent the opinion(s) of HP.
S
8'