Re: [SI-LIST] : Connector pin pwr/gnd ratio

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From: Michael Nudelman (mnudelman@tellium.com)
Date: Mon Nov 13 2000 - 14:39:55 PST


James:

Without knowing your current distribution/type of load/etc - how could anyone
tell?

But one criterion is this: according to Kirchhoff law - the sum of currents
flowing into your 2.5/3.3V pins will make up current flowing out of your GND
pins.

Mike.

"Peterson, James F (FL51)" wrote:

> The original question was meant to be:
>
> On my board (CMOS logic), I have 85 connector pins allotted for 3.3v, 2.5v
> and gnd.
> How would you distribute? and why?
>
> Would you do 25% for 3.3v, 25% for 2.5v, and 50% for gnd? (which is a
> component approach, but maybe not a board approach.)
>
> Would you minimize the pwr pins and maximize the gnd pins? if so, why?
> (don't we have return currents flowing in both.)
>
> all inputs and opinions are welcome and appreciated.
>
> Jim
>
> -----Original Message-----
> From: Charles Grasso [mailto:chasgra@msn.com]
> Sent: Monday, November 13, 2000 4:25 PM
> To: Peterson, James F (FL51); si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : Connector pin pwr/gnd ratio
>
> The allocation of grounds with respect to any number of signals is mainly
> based
> on rise time (hence frequency content). That is to say the faster the rise
> time the
> more grounds you need - the asymptote being a solid "bar" connection found
> in many impedace controlled connectors.
>
> ----- Original Message -----
> From: "Peterson, James F (FL51)" <james.f.peterson@honeywell.com>
> To: <si-list@silab.eng.sun.com>
> Sent: Monday, November 13, 2000 6:57 AM
> Subject: [SI-LIST] : Connector pin pwr/gnd ratio
>
> > Hello,
> >
> > I'm looking for some information on what the pwr/gnd ratio should be for a
> > board's connector. (I know there is something in the archives, but I
> > couldn't find it.)
> >
> > Someone said a rule of thumb is a 3 to 1 ratio, but I'm not sure what that
> > is based on.
> >
> > So let's say for example I have 85 connector pins for 3.3v, 2.5v and gnd.
> > How would you distribute? and why?
> >
> > thanks
> > Jim
> > > Jim Peterson
> > > james.f.peterson@honeywell.com
> > > Honeywell Space Systems
> > > M/S 934-5
> > > 13350 U.S. Hwy 19 N.
> > > Clearwater FL, 33764-7290
> > > Office : 727-539-2719
> > > Fax : 727-539-2183
> >
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