[SI-LIST] Decoupling capacitor range required - PI Analysis

  • From: "Lakshmi Narayanan Sowrirajan, TLS-Chennai" <lakshminarayanans@xxxxxx>
  • To: <si-list@xxxxxxxxxxxxx>
  • Date: Wed, 8 Apr 2009 18:48:50 +0530



            In many papers and books I am seeing that the impedance has
to be maintained across the frequency of interest, which one I have to
take as my interested one is it KNEE frequency or is there any other
formula specifically for PI.


            In the
"Power_Distribution_Networks_with_On-Chip_Decoupling_Capacitors" book
chapter six, summary it is mentioned as follows


            "In order to ensure correct and reliable operation of an IC,
the impedance of the power distribution system should be maintained
below the target impedance in the frequency range from DC to the maximum
operating frequency"


            With this is it enough to keep the impedance constant
(maintained at the Z target) up to 600MHz for a core voltage which is
supplying a core operating at 600MHz.



In the book by Istvan Novak "Power Distribution Network Design
Methodologies" chapter 7 FDTIM method section 7.4 explains the need for
on chip decaps and other important elements of the PDS which supports
the target impedance, but in the tabulation at page 124 uses only up to
10pF capacitor whose resonance Frequency is 50.4MHz, is it given in a
way assuming that after this the impedance will be met with the help of
the on chip package and Die capacitance.


Please clarify this. Thanks all for helping me in this PI topic.



Thanks & Regards





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