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

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From: Kai Keskinen (keskinen@nortelnetworks.com)
Date: Fri Mar 24 2000 - 11:51:38 PST


Adrian:

I suggest you check out some global safety standards. To my last info, -48
in Japan was considered hazardous. Even though it is going away, there are
still some 60V Central offices in Germany and 60V is considered hazardous.
So a -48V nominal product intended for global use can have some safety
regulatory issues regarding access to the voltages. I agree that it is
somewhat stupid. You can't keep people from killing or injuring themselves
with the obvious but why did fast food restaurants put "contents can be
hot" on their coffee cups?

Cheers,

Kai Keskinen
Equipment and Network Interconnect
Nortel Subsystems and Performance Networks (NSPaN)
(613)-765-3506 (ESN 395)
keskinen@nortelnetworks.com <mailto:keskinen@nortelnetworks.com>

        -----Original Message-----
        From: Adrian Shiner [SMTP:adrian.shiner@virgin.net]
        Sent: Friday, March 24, 2000 2:32 PM
        To: si-list
        Subject: Re: [SI-LIST] : Number of GND/Power pins in a
connector ?

        Check out your electricity safety standards! The only way you are
going to get into trouble with 48 volts is by putting it in your mouth or
some other stupid place.
         
        Building sites use 50-0-50 volts centre tap grounded for the simple
reason that it is safe for what is one of the most hazardous places to be
working from any point of view.
         
        Independant of country and their perceptions of risk, if a person
becomes the unwilling subject of gravity, fire, electricity, radiation, high
pressure substances let loose then the result is the same. Not a lot of
people understand this point, especially politicians.
         
        Adrian

                ----- Original Message -----
                From: Kai Keskinen <mailto:keskinen@nortelnetworks.com>
                To: 'si-list@silab.eng.sun.com'
<mailto:'si-list@silab.eng.sun.com'>
                Sent: 24 March 2000 18:49
                Subject: RE: [SI-LIST] : Number of GND/Power pins in a
connector ?

                When the backplane carries nominal -48V, there is a danger
of personnel accessing what is considered a hazardous voltage in some
regions.

                I don't see any reason from an EMI or SI point of view for
having either male or female contacts on the backplane.

                Cheers,

                Kai Keskinen
                Equipment and Network Interconnect
                Nortel Subsystems and Performance Networks (NSPaN)
                (613)-765-3506 (ESN 395)
                keskinen@nortelnetworks.com
<mailto:keskinen@nortelnetworks.com>

                -----Original Message-----
                From: Nerheim, Max [SMTP:max.nerheim@intel.com]
                Sent: Friday, March 24, 2000 1:21 PM
                To: 'si-list@silab.eng.sun.com'
                Subject: RE: [SI-LIST] : Number of GND/Power pins in
a connector ?

                Maybe it could also be a carry-over from UL/TUV safety
requirements: If you
                have a male pin with power on some pins it is more
susceptible to be shorted
                out.

                -----Original Message-----
                From: WILLIAM.GAINES@Aerojet.com [
mailto:WILLIAM.GAINES@Aerojet.com <mailto:WILLIAM.GAINES@Aerojet.com> ]
                Sent: Friday, March 24, 2000 9:29 AM
                To: 'si-list@silab.eng.sun.com'
                Subject: RE: [SI-LIST] : Number of GND/Power pins in a
connector ?

                The usual reason to use male pins on the daughter card is
because it is much
                easier to protect the male pins with a shroud, or connector
placement on the
                pwb. Having male pins on the motherboard makes them very
susceptible to
                damage during assembly and handling.

                Bill Gaines
                Sr. Engineer, Electronic Packaging, Aerojet, Azusa
                626-812-2199 m-f 7-3:30 626-969-5772 fax

                william.gaines@aerojet.com 626-849-2324 pager

> ----------
> From: Lum Wee Mei[SMTP:lweemei@dso.org.sg]
> Reply To: si-list@silab.eng.sun.com
> Sent: Thursday, March 23, 2000 3:18 PM
> To: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : Number of GND/Power pins in
a connector ?
>
> Since we are in this question, I would like to add one :
>
> Is there a preferrence to use female connector on a board?
I was told that
> male connector is not prefer because the pins may acts as
antenna loops
> when the board is left alone.
>
> Can someone enlighten me on this subject?
> Thanks.
>
>
>
> Scott McMorrow wrote:
>
> > Stuart,
> >
> > "It depends" is the correct answer.
> >
> > The best way to size the number of ground and power pins
in
> > a connector is to simulate the regions on either side of
the
> > connector. The connector model should be fully coupled
for
> > all pins including power and ground. You should grid
the ground
> > and power planes around the connector edge and within
the
> > grid include the decoupling capacitors. A connector
swath
> > should be simulated with data transmitted in both
directions
> > (if bidirectional) and driven by worst case driver edge
rates into
> > transmission lines which are referenced to the non-ideal
power
> > and ground grid. Multiple data patterns should be
simulated
> > for worst case pattern sensitivity.
> >
> > These sorts of simulations will answer several
questions:
> >
> > How much data skew and jitter is caused by connector
crosstalk,
> > and return path effects for each ground/power pattern?
> >
> > What happens when a signal is referenced to a ground
plane
> > on one side of the connector and to a power plane on the

> > other side?
> >
> > How much noise is induced by data switching into the
ground and
> > power grids on either side of the connector?
> >
> > What is the worst case instantaneous voltage
differential
> > across the ground pins on either side of the connector?
> >
> > What is the worst case instantaneous voltage
differential
> > across the power pins on either side of the connector?
> >
> > And for bonus points:
> >
> > If you have accurate modeling of the power switching
currents of
> > the devices on either side of the connector, you can
simulate the
> > worst case connector and plane noise due to power
transients
> > and data switching transients.
> >
> > Depending on the edge rate and the quality of the
connector you
> > may find that although you need few power and ground
pins to
> > facilitate clean power delivery, you may need many more
power
> > and ground pins to facilited clean signal delivery.
> >
> > regards,
> >
> > scott
> >
> > --
> > Scott McMorrow
> > Principal Engineer
> > SiQual, Signal Quality Engineering
> > 18735 SW Boones Ferry Road
> > Tualatin, OR 97062-3090
> > (503) 885-1231
> > http://www.siqual.com <http://www.siqual.com>
> >
> > Stuart Adams wrote:
> >
> > > 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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