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Re: 3.3V on a 5V bus
- To: Mailing List Recipients <pci-sig-request@znyx.com>
- Subject: Re: 3.3V on a 5V bus
- From: "John R Pierce" <pierce@scruznet.com>
- Date: Sat, 16 Nov 1996 13:22:10 -0800
- Resent-Date: Sat, 16 Nov 1996 13:22:10 -0800
- Resent-From: pci-sig-request@znyx.com
- Resent-Message-Id: <"dJf1n1.0.y7.B3ZZo"@dart>
- Resent-Sender: pci-sig-request@znyx.com
> Let's say I'm designing a board to plug into a 5V PCI bus, but I have some
> part that really *needs* 3.3 V.
>
> Obviously, the spec requires me to put a regulator on my board to generate
> 3.3V from the 5V rails.
>
> Am I supposed to connect "my" 3.3 V back out to the 3.3V pins at the edge
> of my card ? (So that I can use the host computer's 3.3V regulator, if it
> *is* present, which is bound to be better EMI shielded, have better
> efficiency, have better cooling, etc.).
NO, NO, and NO. Do NOT connect your internal 3.3V to the systems' 3.3V!
"