AW: [SI-LIST] : High Permittivity Board Level Decoupling and rela ted

Neibig Uwe (Uwe.Neibig@pcm.bosch.de)
Tue, 16 Jun 1998 11:10:34 +0200

Hi Elya,

another important point to take into account is the freqency dependence of
the (complex)
permittivity of your dielectric material. For example if epsilon_r is
decreasing with frequency the effect of enlargening the electical dimensions
of the pcb maybe less severe at higher frequencies.

Regards, Uwe Neibig

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Robert Bosch GmbH phone: +49 711 811 20026
K3/EDK
fax: +49 711 811 1100
Dr.-Ing. Uwe Neibig e-mail: Uwe.Neibig@pcm.bosch.de
P.O.Box 30 02 40
70442 Stuttgart
GERMANY
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> ----------
> Von: Elya B. Joffe[SMTP:ebj@netvision.net.il]
> Gesendet: Montag, 15. Juni 1998 23:58
> An: SI-LIST@silab.Eng.Sun.COM
> Betreff: Re: [SI-LIST] : High Permittivity Board Level Decoupling and
> related issues
>
> Dear Members,
>
> a) High Permittivity Dielectrics
>
> We are considering to use, for RF and ultra-high speed digital circuits,
> very high permittivity dielectrics between the PCBs ("Thick Film FODEL").
>
>
> Assume a separation between GND and VCC of 1.6mil, and a dielectric
> constant Epsilon(r) of 5,000.
>
> We have calculated that for a sq. Inch of PCB this is "worth" about 700nF
> of decoupling.
>
> In this case, would discrete decoupling capacitors actually be necessary,
> would they be of any avail or perhaps even the opposite? Any input on this
> will be greatly appreciated.
>
> b) Analog Circuit Decoupling
>
> Does anyone know any "rule of thumb" for selecting the proper value of
> decoupling capacitors for analog circuits? In digital circuits - the rise
> time and switching currents of the devices play an important role... What
> are the considerations in Analog circuits???
>
> Any reply to either or both questions will be greatly appreciated.
>
> Thanks alot,
>
> Elya B. Joffe - EMC Engineer
>
> Every success begins with the launching of a dream
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