[SI-LIST] Re: Heat Sink Hook Grounding
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Sanjay G <myworld_sg@xxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Sun, 30 Mar 2014 12:36:25 -0700
Sanjay partial inductance is an artificial method of representing the
incremental effect on inductance due to a portion of an overall
structure. Please separate the concept of partial inductance from the
fact that there is no isopotential. How finely a model should be broken
down depends on how you are trying to use the model. Chip_vss may
itself be broken into many nodes. How you determine coefficients for
your model elements is a different issue.
Steve.
On 3/30/2014 4:09 AM, Sanjay G wrote:
> Steve
> if I want to understand your reply in simpler language then I assume
> you support the idea of using artificial (but very useful) terms in
> overall simulation topology involving chip, package, ground. For
> example...
> chip_vss -> bump_vss - > ball_vss -> board_vss
>
> all these vss terms are artificial. But, any two vss can be connected
> through partial inductance as below.
>
> chip_vss <--(partial VSS L between pad and bump)) -> bump_vss
> <--(package VSS partial inductance b/w bump and ball) --> ball _vss
> --> partial L of the board VSS plane)
>
> similarly VDD plane can be connected using partial L element
>
> chip_vdd <--(partial VDD L between pad and bump)) -> bump_vdd
> <--(package VDD partial inductance b/w bump and ball) --> ball _vdd
> --> partial L of the board VDD plane)
>
>
> I hope this is not weird method of simulating ground bounce (even
> though this is artificial term) involving system topology (IO->pkg->board)
>
> Many experts have suggested that there should be no different in
> results if loop inductance is used in place of partial inductance.
> But, in that case, all vss (chip,pkg,board) will be connected to ideal
> vss.
>
> I am not sure, which method is correct partial L vs Loop L ? should
> both approach give similar results?
>
>
> Thanks
> Sanjay
>
>
> On Sunday, March 30, 2014 2:24 AM, steve weir <weirsi@xxxxxxxxxx> wrote:
> My argument for suppressing the use of "ground" is that "ground" has
> taken on so many erroneous colloquial meanings as to become a
> "marklar". I think that suppressing the term "ground" and instead
> saying "chassis common", or "earth" or "Vss" or "circuit common", when
> that is what we really mean forces people to think more clearly about
> the function a particular interconnect or chunk of metal performs.
> Using specific terms for each function I think is much less likely to
> engender magical properties that many engineers erroneously ascribe to
> the term "ground". I think that this is even more so in systems that
> have high energy and power potentials like those that you mention. How
> good is a safety return that can electrify 50 volts above the floor
> under a fault current condition or get so hot that it sets insulation on
> fire? How useful is a safety return that electrifies to just a couple
> of volts in a medical environment? I have seen many times engineers
> use inappropriate interconnects because of their religious faith in a
> nodal connection to "ground".
>
> Steve
> On 3/29/2014 8:09 AM, Todd Hubing wrote:
> > While I agree that it may be best for signal integrity engineers to
> let go of the term "ground", the concept of ground is very important
> for system-level design (particularly for industrial, automotive and
> aviation systems). In these systems, improper grounding is a major
> cause of EMC and product safety issues.
> >
> >
> > Lately, we've been hearing a lot of presentations advocating that
> there is "no place called ground" or that "ground is a place where
> carrots and potatoes grow". This may be exactly what high-speed signal
> integrity engineers need to hear, since their current return
> conductors are often labeled "ground". But rather than suggesting that
> "ground" is an irrelevant concept, I think it better to point out that
> "ground" and "current return paths" serve two different and often
> incompatible functions.
> >
> >
> >
> > Todd
> >
> > -----------------------------------
> >
> > Todd Hubing
> >
> > Michelin Professor of Vehicle Electronics
> >
> > Clemson University
> >
> > Clemson, SC 29634 USA
> >
> >
> >
> > LearnEMC.com
> >
> > -----------------------------------
> >
> >
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>
> [mailto:si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>] On Behalf Of steve weir
> > Sent: Saturday, March 29, 2014 2:18 AM
> > To: Sanjay G; si-list@xxxxxxxxxxxxx <mailto:si-list@xxxxxxxxxxxxx>
> > Subject: [SI-LIST] Re: Heat Sink Hook Grounding
> >
> >
> >
> > The path to recovery for ground-aholics is to put their faith in
> Maxwell's equations and let go of the term "ground". There is a green
> wire safety connection to earth. Designs have Vss planes, chassis and
> other metallic structures that may have a DC path to the green safety
> wire. At any appreciable frequency these structures are not
> iso-potentials.
> >
> > You know that you have done an adequate job when the EMFs in your
> design all fall within acceptable limits.
> >
> >
> >
> > Partial inductance is an artificial but very useful concept. Some
> people don't like it like some people don't like GO TO statements in
> code, even though they have no problem with Switch / Case statements
> which simply hide GO TO statements. Use what is practical and works.
> >
> > Appreciate and respect the limitations of partial inductance and it
> can be very practical and useful. EMI no different than any other E/M
> except that we want to limit how much of it gets out of our products.
> >
> >
> >
> > Steve.
> >
> > On 3/28/2014 7:20 PM, Sanjay G wrote:
> >
> >> Hi Steve,
> >> 'When you say there is no place like ground'. it is all differential
> >> potential which should be considered for any design consideration.
> >> How do I know whether my Ground plane design is good or bad. Power
> >> plane design is good or bad.
> >> In some of the SI-list post regarding partial inductance vs loop
> >> inductance, some people never believe in partial inductance model,
> >> they only believe in overall loop inductance. they claim even if two
> >> inductance matrix with different partial inductance but similar loop
> >> inductance should give similar results. does this assumption valid
> >> for EMI radiation also?
> >> Thanks,
> >> On Friday, March 28, 2014 1:40 AM, steve weir <weirsi@xxxxxxxxxx
> <mailto:weirsi@xxxxxxxxxx><mailto:weirsi@xxxxxxxxxx
> <mailto:weirsi@xxxxxxxxxx>>> wrote:
> >> Indeed.
> >> In the famous story and movie: "The (Wonderful) Wizard of Oz" Dorothy
> >> must repeat: "There is no place like home." Dr. Bruce Archambeault
> >> teaches us that we must repeat: "There is no place called ground."
> >> Difference potential along the structure will radiate. The more
> >> inductance, the lower the frequencies and the stronger the radiation
> >> as well as the greater the susceptibility that you point out. A
> >> clever person like Doug Smith might point out that there is an optimum
> >> resistance to place between the heat sink and the board to minimize
> >> resonant peaking.
> >> This could make a good EMC demonstration.
> >> Steve.
> >> On 3/27/2014 12:52 PM, Antonis Orphanou wrote:
> >>> A floating heat-sink is coupled to the rest of the PKG/PCB
> >> arrangement by surface capacitance. It will radiate based on half
> >> wavelength modes.
> >>> Providing now a conductive path of the heat-sink to the rest of the
> >> circuit arrangement you have eased the current flow to the antenna
> >> (heat-sink). The same antenna is now driven by a stronger source and
> >> depending on the dimension of the grounding path (at some point in
> >> frequency it will be an open inductive path) you will see an increase
> >> in the total power radiated by your heat-sink, as well as radiated
> >> power accepted by the same topology.
> >>> -----Original Message-----
> >>> From: si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx><mailto:si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>>
> >> <mailto:si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>>
> >> [mailto:si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>
> >> <mailto:si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>>] On Behalf Of Ranjith
> >> Raviprakash
> >>> Sent: Thursday, March 27, 2014 9:57 AM
> >>> To: si-list
> >>> Subject: [SI-LIST] Heat Sink Hook Grounding
> >>> Hi Experts,
> >>> What is the impact of grounding Heat sink anchors?
> >>> I want to use them as probe ground points for measurement during
> >>> proto bring-up (by removing the anchors and using a male header)
> >>> During final shipment, I will place the anchors back and of course
> >>> they will remain grounded.
> >>> Ranjith
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> >> --
> >> Steve Weir
> >> IPBLOX, LLC
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> > --
> >
> > Steve Weir
> >
> > IPBLOX, LLC
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> > 1580 Grand Point Way
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> > MS 34689
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> > Reno, NV 89523-9998
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> --
> Steve Weir
> IPBLOX, LLC
> 1580 Grand Point Way
> MS 34689
> Reno, NV 89523-9998
> www.ipblox.com
>
> (775) 299-4236 Business
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