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Re: 3.3V Decoupling
- To: Mailing List Recipients <pci-sig-request@znyx.com>
- Subject: Re: 3.3V Decoupling
- From: ivor@peritek.com (Ivor Bowden)
- Date: Fri, 22 Nov 1996 08:04:01 -0800
- Cc: sabath@atla3.agfa.com
- Resent-Date: Fri, 22 Nov 1996 08:04:01 -0800
- Resent-From: pci-sig-request@znyx.com
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Comment to Andy Ingraham's post:
If you look at the connector pinout you notice every signal is paired with a (AC) ground, typically in a
(AC)gnd - signal - signal - (AC)gnd - signal - signal - (AC)gnd....
pattern.
Good reason to make sure those 5V and 3.3V (AC gnd) pins are well bypassed.
Excerpt from Andy Ingraham's original post:
>Correct. Except that it's not just the raw number of ground pins on
>the connector. You need to look at the power+ground pins in the
>immediate vicinity of a given signal pin. Most of the +3.3V pins
>displace what would have been ground pins around the middle of the
>connector, leaving the concentration too low in that area. The +5V
>pins do the same in other parts of the connector. But that's allright
>because PROPERLY BYPASSED power pins work almost as well for the
>purpose of the AC return path.
>
--------------------
standard disclaimers:
I speak for myself.
My views may not be the same as my employer's.
Ivor Bowden
Peritek Corp
; ô á