Re: deriving 3.3V from 5V ..

["Peter Marek" <peter.marek@marekmicro.de>]

Hi,

 

up to PCI revision 2.1, supplying 3.3V on 5V PCI slots was optional. Supplying 3.3V in any PCI environment is madatory since PCI Rev. 2.2.

 

So, it's common practice to use a LDO regulator to derive 3.3V from the 5V supply to make sure taht your PCI board works even in some of these "old" PCs.

 

Regards,

 

Peter Marek
General Director
MarekMicro GmbH
tel.: 049-9621-9732-110
fax: 049-9621-9732-199
www.marekmicro.de

----- Original Message -----

From: dinesh@cosystems.com

To: pci-sig@znyx.com

Sent: Thursday, December 06, 2001 5:26 AM

Subject: deriving 3.3V from 5V ..

Hi experts,

 

Sub: Universal PCI card

 

I have referred a number of universal PCI card designs. One point I have noticed is, none of the cards are using the 3.3V supply from the slot - instead deriving the 3.3V from 5V by putting a regulator.But even 5V PCI slots are provided with 3.3V supply rails. Is there any solid reason for this ??

 

thanks in advance

Din