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

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From: S. Weir (weirsp@a.crl.com)
Date: Fri Mar 24 2000 - 18:35:40 PST


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: <mailto:keskinen@nortelnetworks.com>Kai Keskinen
>>To: <mailto:'si-list@silab.eng.sun.com'>'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)
>><mailto:keskinen@nortelnetworks.com>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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