RE: [SI-LIST] : Number of GND/Power pins in a connector ?

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From: Chris.H.Simon@gd-is.com
Date: Thu Mar 23 2000 - 09:11:26 PST


I would agree with Gregg Fokken's comments. But I have a question on the details.

I suspect that when you say "... your board is well bypassed ..." it implies that there
must be adequate decoupling on BOTH the board being plugged in through the connector, and
the board being plugged into. Is this correct?

This would allow the transient signal currents in the multilayer structures on each side
of the connector to traverse between power and ground planes without generating excessive
noise or EMI. If only one side of the connector had adequate bypass capacitance (where
the term "adequate" is another discussion) then the signals coming from the other side may
cause problems.

Is this correct or is it adequate to bypass just one side of the connector, or does it
depend on whether signals are moving in both directions through the connector?

Chris Simon
General Dynamics Information Systems

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If you're using CMOS rail-to-rail, your GND connector pins will see
essentially the same switching current that you're PWR pins will see.
However, if your board is well bypassed as you say, then you don't need to
worry about switching current in either PWR or GND pins at the board edge
(only steady-state as you mention).

> -----Original Message-----
> From: Stuart Adams [mailto:sja@brightstareng.com]
> Sent: Thursday, March 23, 2000 9:43 AM
> To: si-list@silab.eng.sun.com
> Subject: [SI-LIST] : Number of GND/Power pins in a connector ?
>
>
>
> How do I calculate the number of ground and power
> pins I need in a board-to-board connector.
>
> The number of grounds is a function of switching
> current and how many signals will switch at the same
> time, correct ?
>
> More grounds is always better but what about power pins ??
>
> If one or two pins are sufficient to carry the max steady
> state current and my board is well bypassed with bulk and
> ceramic caps, is there a need for alot more power pins ?
>
> -- Stuart

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