[SI-LIST] Re: Decoupling at 800Mhz

  • From: "Aravind Sandeep" <aravind.sandeep@xxxxxxxxx>
  • To: "Subramanian R" <subramanian1683@xxxxxxxxx>
  • Date: Fri, 23 May 2008 10:30:18 +0530

Hi Subramanian,
At high frequency the conventional decoupling capacitor looks like Besides
the pure capacitance there is an Equivalent Series Inductance ESL and an
Equivalent Series Resistance ESR.Capacitor shows capacitive behaviour in the
lower frequency range; for frequencies higher than the series resonant
frequency the behaviour becomes inductive. Optimum decoupling effect is
found at series resonant frequency. This information should be available in
capacitor data sheets. Although this information is given in the capacitor
data sheet i would recommend to use a simulations before you proceed for
prototyping.

Thanks and Regards,
Aravind



On 5/22/08, Subramanian R <subramanian1683@xxxxxxxxx> wrote:
>
> Hi All,
> We are planning to use a processor running at 800 MHz.
> I was just reading up on the decoupling methods.
>
> The Processor PCB guidelines recommend using 1uF 0402 pack for high
> frequency decoupling. But at 800 MHz, will not the cap/package inductance
> dominate.
>
> The guideline doesn't say anything about plane decoupling also.
>
> Am I missing something? What are the best approaches for decoupling?
>
> Any suggestions will be very useful.
>
> Thank you in advance,
>
> Regards
> Mani
>
>
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