[SI-LIST] Re: Decoupling for PLL

Mike,

> The 3db point
> is
> Around 10Khz.
...
> I also simulated with a Tant. Cap instead of cer cap ...
> The draw back is the 3db point now at 100Kz.

What were the values of your ceramic and tantalum caps?

If must be either a small tantalum cap, or a large ceramic, for the filter's
cutoff frequency to have gone UP that much with the tantalum.

> If the peak
> happens at a non-existing frequency, why do I care?

If the peak isn't severe, maybe you don't.  However, in many circuits,
chances are that sooner or later, something like a data pattern may come
along that excites that resonance, and causes problems.  In any event, a
high-Q peak is just plain trouble.  Off-frequency transients would cause
it to ring.

Regards,
Andy


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