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

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From: Adrian Shiner (adrian.shiner@virgin.net)
Date: Sat Mar 25 2000 - 04:27:13 PST


From my involvement in working on EN and ISO standards, it is apparent that there is a long term drive to harmonise standard world wide, based on the European Union standards. This will provide a more consistent (based on hazard and risk assessment), approach to the matter of protecting people from the consequences of playing with equipment having live and stored energy sources. In the UK, there is a general requirement to work on electrical equipment with all energy sources isolated and discharged unless there is a good reason to work "live". Working "live" requires competant persons, suitable tools and methods. This comes from the Electricity at Work Regulations. They do not define any voltage level as "safe" for non compliance with this requirement.

It is of interest to note how many desk top toys seem to have capacitive filters attached to the pins of IEC connectors waiting to catch the unwary person who moves the thing just after switching off the supply. No warning notice near the connector either. I know one lady who got a nasty (for her) surprise when her fingers touched the pins in such a connector when she was rearranging her office and decided to move the computer

Best wishes

Adrian
  ----- Original Message -----
  From: S. Weir
  To: si-list@silab.eng.sun.com
  Sent: 25 March 2000 02:35
  Subject: Re: [SI-LIST] : Number of GND/Power pins in a connector ?

  Adrian,

  In the US, the UL ELV limit is 42.4V. They used to look the other way at telco battery voltage, but no longer,

  Regards,

  Steve

  At 07:31 PM 3/24/2000 +0000, you wrote:

    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 > > > > > > **** To unsubscribe from si-list or si-list-digest: send e-mail to > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > > > si-list archives are accessible at http://www.qsl.net/wb6tpu > > > **** > > > > **** To unsubscribe from si-list or si-list-digest: send e-mail to > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > > si-list archives are accessible at http://www.qsl.net/wb6tpu > > **** > > > **** To unsubscribe from si-list or si-list-digest: send e-mail to > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > si-list archives are accessible at http://www.qsl.net/wb6tpu > **** > **** To unsubscribe from si-list or si-list-digest: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu ****

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