[SI-LIST] Re: Bypass vs Decoupling capacitors
- From: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>
- To: <cpad@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>, "steve weir" <weirsp@xxxxxxxxxx>
- Date: Thu, 26 Aug 2004 20:48:29 -0400
Steve,
Eventually it is a judgement call of the designer. If you have to
increase the number of layers by one (and to keep the stackup
symmetry, it is never just one), the board cost may go up by
$5-15, depending on the size and complexity. For that money
one can buy many hundred resistors and capacitors to quiet
the planes.
Regards,
Istvan
> Istvan, yes on most of the points we agree. There are always exceptions
to
> any hard rule. A large Vcc plane that does not have thin / lossy
> dielectric is subject to resonance at pretty low frequencies. So in the
> cost equation, we have to figure out which costs more:
>
> 1) Dealing with the increased route complexity of an islanded scheme
> 2) Buying lossy dielectric, or special parts / materials to edge terminate
> the planes.
>
> I am very biased towards 1)
>
> Regards,
>
>
> Steve.
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