Re: did you receive this via si-list ??

Larry Smith ([email protected])
Thu, 1 May 1997 14:11:47 -0700

Yes, I saw this earlier this week. I got my copy, did you get yours?

Larry

> From [email protected] Thu May 1 14:08:12 1997
> Date: Thu, 1 May 1997 14:00:43 -0700
> From: [email protected] (Ray Anderson)
> To: [email protected]
> Subject: did you receive this via si-list ??
>
>
>
> This came in via the si-admin bounce route. Don't remember seeing it on
> the main list. Did you ?? (Might have been enroute when we downed silab to
> move it.)
>
> -Ray
> ----------------------------------------------------------------------------
> From: "Bob Techentin" <[email protected]>
> Message-Id: <[email protected]>
> Date: Mon, 28 Apr 1997 14:51:15 -0500
> In-Reply-To: [email protected] (Andy Ingraham)
> "Power/ground connections/bypassing on ICs" (Apr 28, 11:40am)
> References: <[email protected]>
> Reply-To: "Techentin, Robert W." <[email protected]>
> X-Mailer: Z-Mail (3.2.1 10oct95)
> To: [email protected] (Andy Ingraham)
> Subject: Re: Power/ground connections/bypassing on ICs
> Cc: [email protected]
> Mime-Version: 1.0
> Content-Type: text/plain; charset=us-ascii
>
> Andy,
>
> You made the statement:
> > The power/ground planes are your best high frequency bypass
> > capacitor
>
> This isn't always true. Power and ground planes are, in fact,
> inductive at frequencies between the first "system" resonant frequency
> and the first "modal" resonant frequency. The first modal resonant
> frequency is at f=1/(2*L*sqrt(u*e)) where L is the largest (x or y)
> dimension of the power plane, and u and e are the permeability and
> permittivity of the dielectric, respectively. The system resonant
> frequencies are more difficult to locate, but they can be computed by
> summing a wide range of modal impedances.
>
> As long as "high frequency" is lower than than the power/ground
> system's resonant frequencies, then L*di/dt and all your basic circuit
> assumptions will work. Once you get above that, then the modeling
> problems and solutions get a lot harder. Just for example, when our
> group built several 450 MHz digital signal processor prototypes in the
> early 1980s, it was necessary to include decoupling capacitors on top
> of (and in some cases even inside of) the IC packages.
>
> --
> Bob Techentin [email protected]
> Mayo Foundation http://www.mayo.edu/sppdg/
> Rochester MN, 55905 USA (507) 284-2702
>
>