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

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From: Adrian Shiner (adrian.shiner@virgin.net)
Date: Fri Mar 24 2000 - 11:31:45 PST


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
  To: '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

    -----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]
    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
> >
> > 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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