RE: 5V vs. 3.3V signaling

["John Bloomfield" <john@datacube.com>]

Be careful about capacitance. In such a use of these parts 
the switch is always on or closed. That means that the PCI 
pin on the edge connector sees the capacitance of both sides 
(pins) of the switch as well as the pin capacitance of your 
"adapter card PCI interface chip".

Without doing the numbers, I would be surprised if this did
not violate the spec. 


John Bloomfield
VP Hardware Engineering
Datacube Inc. 300 Rosewood Drive Danvers, MA 01923
Voice: 978-777-4200 Email: john@datacube.com  

> -----Original Message-----
> From: Ivor Bowden [mailto:ivor@peritek.com]
> Sent: Friday, August 25, 2000 3:51 PM
> To: Alex Horvath
> Cc: pci-sig@znyx.com
> Subject: Re: 5V vs. 3.3V signaling
> 
> 
> I think IDT (www.idt.com) has a "bus switch" line,
> these are 0 nS prop delay bi-dir switches that can
> be used for 5-3 V translation. Don't know how
> appropriate they might be for this app, though.
> I think they have generic 5-3 interface app note
> on their web site.
> Ivor
> 
> At 11:27 AM 8/25/00 -0700, you wrote:
> >I have a  system that I need to design a adapter card for that uses 5V
> >signaling but my adapter card PCI interface chip only supports 3.3V
> >signaling. Someone suggested that I use a "translator" chip that takes
> >3.3V PCI signals and converts them to 5V and vice versa (of course with
> >virtually zero delay) but I doubt anything like that exists. The other
> >possibility, although brute force, is to use a PCI-PCI bridge which
> >supports both signaling standards. Anybody ever confront this problem?
> >
> >--
> >Alex Horvath
> >ahorvath@cisco.com
> >Cisco Systems
> >190 West Tasman Dr.
> >San Jose, CA 95134
> >Voice: 408-853-3289
> >
>