[SI-LIST] Re: Digest Number 885

  • From: s s <ssankarsin24@xxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Mon, 27 Oct 2003 09:47:08 -0800 (PST)

Hi All,
I am a student and am interested in learning SI . I was wondering if someone 
could please suggest me some introductory books on SI.
 
Thanks
Shankar
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There are 10 messages in this issue.

Topics in this digest:

1. Re: Sacrificial ground: Is it useful?
From: MikonCons@xxxxxxx
2. testing
From: "A.Z." 
3. Field-solver
From: "elecqs" 
4. Re: Sacrificial ground: Is it useful?
From: MikonCons@xxxxxxx
5. About the limit of minimum length
From: "Fu, Greg (¸¶?V²Ù IES)" 
6. Re: What are the differencs between W, T and U-element of a tranmission line 
model?
From: Sudheer B S 
7. Re: What are the differencs between W, T and U-element of a tranmission line 
model?
From: "Jack" 
8. Re: Sacrificial ground: Is it useful?
From: Geoff Stokes 
9. Re: How to build a variable resistor in HSPICE
From: Antonio Girardi 
10. Re: What are the differences between W, T and U-ele ment of a transmission 
line model?
From: "Clewell, Craig" 


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Message: 1
Date: Sun, 26 Oct 2003 18:00:28 EST
From: MikonCons@xxxxxxx
Subject: Re: Sacrificial ground: Is it useful?

John:
You were wondering about the source for chassis-grounded guard traces around 
PCBs. I believe I'm the guilty party. Back in 1989, I devised a method to 
protect board devices from ESD while reducing radiated emissions as well. I 
generated the concept with the following guidelines.

Place a ring around the PCB periphery of 50 (or more) mils width on EVERY 
layer. The outter layers should have a soldermask setback (i.e.,to expose the 
conductor). Use stagger-spaced vias to connect all rings, forming a low 
inductance conducting strap around the PCB periphery. The ring structure should 
be 
connected to the primary signal reference entry point (generally at a connector 
interface).

The guard ring concept has multiple purposes:
a) Providing a field termination point for radiated emissions originating on 
the PCB.
b) Providing a sacrificial/preferred ESD strike area with a current 
distribution mechanism.

Item (a) is most beneficial where common-mode excitation exists on the planes 
(e.g., in the case of planar resonances) of the PCB, but also serves to 
intercept signals from the many inadvertent loop and monopole antennas that are 
unavoidably formed in most any PCB layout. The ring provides the preferred path 
back to the local ground reference for the PCB. Hence, the ring provides a 
local termination and return path for any fields emanating from the PCB 
circuits 
and power/ground plane edges.

Item (b), by virtue of an exposed conductive structure, presents the most 
likely strike area for any ESD buildup. The low inductance of the parallelled 
layer structure minimizes potential differences around the PCB. If a strike 
occurs, the charge is quickly distributed around the PCB and is fed into the 
PCB 
interior via the primary reference ground connection and appears as common-mode 
voltage to the PCB circuits. Theh result is minimal disturbance (under the 
circumstances


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Message: 2
Date: Sun, 26 Oct 2003 15:09:55 -0800
From: "A.Z." 
Subject: testing

test

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Message: 3
Date: Sun, 26 Oct 2003 15:20:07 -0800
From: "elecqs" 
Subject: Field-solver

Hi, up to what frequency has the internal field-solver of Hspice been
correlated? 
Rgds,

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Message: 4
Date: Sun, 26 Oct 2003 18:28:55 EST
From: MikonCons@xxxxxxx
Subject: Re: Sacrificial ground: Is it useful?

Darn, sorry guys, but I lost over half of my comments to John on the last 
E-mail. I didn't save it, so here's a brief summary of what "disappeared."
The result is minimal disturbance (under the circumstances) because of the 
use of the low inductance current path and the lowest current density entry 
point to the internal circuits of the PCB.

RE: Capacitors around the periphery

I recommended PROVISIONS for "spoiler" capacitors be spaced around the ring 
at varying intervals. Because the ring forms a loop antenna that is resonant 
at a low to intermediate frequency, a susceptibility coul be encountered, 
depending on the using environment. If so, addition of either capacitors or low 
value damping resistors could be used to "spoil" or significantly reduce the 
susceptibility. These mounting provisions are not recommended to be populated 
unless a problem is encountered.

The guard ring approach solved many ESD problems, particularly on portable 
designs. I presented the concept in lectures across the US and Europe, as well 
as incorporating custom variations in many designs over the years. Perhaps many 
designers now use the concept without understanding whether they have need 
for it in their particular design.

I had considerably more to comment, but don't have any more time now.

Have fun,


Mike

Michael L. Conn
Owner/Principal Consultant
Mikon Consulting
Cell: 408-821-9843

*** Serving Your Needs with Technical Excellence ***


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Message: 5
Date: Mon, 27 Oct 2003 10:09:17 +0800
From: "Fu, Greg (¸¶?V²Ù IES)" 
Subject: About the limit of minimum length

Content-Type: text/plain;
charset="GB2312"
Content-Transfer-Encoding: quoted-printable
Hi, guru:
I am a novice on this mail list, I have a simple problem.
The model is described:
=20
The design has a rule, which is the length of driver to via must be =
among minimum length and maximum length. But the problem is why it has a =
minimum length? We know, when the length is longer, crosstalk maybe =
increases much. Why ? Anyone who can explain in examples will be greatly =
appreciated. Thanks in advance.
=20
Best regards,
Greg
Mailto:fu.greg@xxxxxxxxxxxx=20
Inventec(ShangHai) Co.,Ltd. =20
=20



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Message: 6
Date: Mon, 27 Oct 2003 10:11:44 -0500
From: Sudheer B S 
Subject: Re: What are the differencs between W, T and U-element of a 
tranmission line model?

T : Lossless transmission line model , single signal only
Can be used for reflection analysis when lengths are less than 
the critical length
U: Lossy Transmission lines allows upto few lines i am not sure of 
this no
probably 4 
W : Lossy Transmission line , Fast , accurate and robust than U 
element and you can simulate
any no of signals



Regards
SUDHEER

lee yang wrote:

>Hi all,
>Any explaination or material on these is much appreciated!
>-LY
>
>
> 
>
>>From: "lee yang" 
>>Reply-To: changly_80@xxxxxxxxxxx
>>To: si-list@xxxxxxxxxxxxx
>>Subject: [SI-LIST] What are the differencs between W, T and U-element of a 
>>tranmission line model?
>>Date: Tue, 21 Oct 2003 11:05:41 +0000
>>
>>Hi,
>>
>>Could some one explains that what are the differences between W, T and
>>U-element of a transmission line model? How do i know which type of
>>transmission line model should I use in my simulation?
>>Thanks.
>>
>>Regards,
>>LY
>>
>>_________________________________________________________________
>>Are you in love? Find a date on MSN Personals http://match.msn.com.my/
>>
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>> 
>>
>
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Message: 7
Date: Sun, 26 Oct 2003 21:25:55 -0800
From: "Jack" 
Subject: Re: What are the differencs between W, T and U-element of a 
tranmission line model?

All,

Could someone refresh my memory:
Field solver like Maxwell 2D output into a file that Hspice references
for the
physical description of the stackup and transmission lines???
Then call this file as a lib that you can denote its length??

thanks,

jack ~


----- Original Message -----
From: "Sudheer B S" 
To: 
Cc: 
Sent: Monday, October 27, 2003 7:11 AM
Subject: [SI-LIST] Re: What are the differencs between W, T and U-element of
a tranmission line model?


> T : Lossless transmission line model , single signal only
> Can be used for reflection analysis when lengths are less than
> the critical length
> U: Lossy Transmission lines allows upto few lines i am not sure of
> this no
> probably 4
> W : Lossy Transmission line , Fast , accurate and robust than U
> element and you can simulate
> any no of signals
>
>
>
> Regards
> SUDHEER
>
> lee yang wrote:
>
> >Hi all,
> >Any explaination or material on these is much appreciated!
> >-LY
> >
> >
> >
> >
> >>From: "lee yang" 
> >>Reply-To: changly_80@xxxxxxxxxxx
> >>To: si-list@xxxxxxxxxxxxx
> >>Subject: [SI-LIST] What are the differencs between W, T and U-element of
a
> >>tranmission line model?
> >>Date: Tue, 21 Oct 2003 11:05:41 +0000
> >>
> >>Hi,
> >>
> >>Could some one explains that what are the differences between W, T and
> >>U-element of a transmission line model? How do i know which type of
> >>transmission line model should I use in my simulation?
> >>Thanks.
> >>
> >>Regards,
> >>LY
> >>
> >>_________________________________________________________________
> >>Are you in love? Find a date on MSN Personals http://match.msn.com.my/
> >>
> >>------------------------------------------------------------------
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> >>
> >>
> >>
> >
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Message: 8
Date: Mon, 27 Oct 2003 08:38:03 -0000
From: Geoff Stokes 
Subject: Re: Sacrificial ground: Is it useful?

Hi John,

Some years ago, equipment in rack assemblies (sonar for example) used to
have a "frame continuity" network. This network was isolated from the rest
of the system except that it was joined at one point to the power supply
ground. All the power returns of each electronic assembly where separately
returned to a star-point ground terminal near the power supply unit. At
that time, there was very little digital processing - it was slow - and high
frequencies greater than 1MHz or so where not really of any concern. The
idea was that a ground loop would be set up if the units were grounded at
more than one point. Any such ground loop would be susceptible to inductive
mains frequency coupling, and with lots of unscreened analog circuits in the
system, this could easily be demonstrated if a unit was wrongly wired!

I think maybe that kind of thinking has now changed and been replaced by a
requirement for tight bonding between well-shielded units. Where necessary,
isolated power supplies and differential signal interconnects or optical
coupling are used for sensitive situations. Could it be that for lower
frequencies, the Frame Continuity principle is still useful? However it
seems to me that the decoupling caps you mention around the edges of the
boards could possibly present a problem, coupling noise in at mid to low
frequencies.

Cheers
Geoff
> -----Original Message-----
> From: John Coupland [mailto:coupswork@xxxxxxxxxxxxx]
> Sent: 24 October 2003 17:59
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Sacrificial ground: Is it useful?
> 
> 
> Hi gurus,
> We've traditionally used a "sacrificial ground" (a 
> trace around the edge of PCBs) which is connected to 
> chassis ground (when the board is installed). We also 
> distribute some caps (like 0.1uF) from this trace to 
> signal ground around the edge of the PCB.

=== message truncated ===


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