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

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From: S. Weir (weirsp@a.crl.com)
Date: Sat Mar 25 2000 - 15:52:18 PST


Adrian,

That incident is a bit strange. Most off-the-line input filters are
configured with a full-wave bridge in front of the bulk capacitors when set
for 220-240V input. In that situation, there isn't a low impedance path
for the capacitor charge to come back to the input connector. Various
standards also call for bleed circuits, although the bleed can be quite
slow. It may have just been a defective unit. We generally work hard not
to endanger our customers / craftspeople.

Regards,

Steve.
At 12:27 PM 3/25/2000 +0000, you wrote:
> 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: <mailto:weirsp@a.crl.com>S. Weir
>>To: <mailto:si-list@silab.eng.sun.com>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: <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 > > > > > > **** To
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