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Plane Noise, Z profile a discrepancy that I can't understand

Question asked by oscar.martinelli on Jul 28, 2012
Latest reply on Aug 9, 2012 by cristian.filip

Dead All,

Working with linesim I have designed a very simple pds that include a couple of plane, a vrm, a C, and one IC PIN. Very easily I have extract the z profile up to 100Mhz in the IC pin area.

 

Then I have tried to run the plane noise simulation after have applied a sinusoidal stimulus to the IC pin.

 

My question is: why I am not able to get the same voltage noise value from the two analisys?

Example:

1. From decoupling analisys at 20Mhz, Z=0.1 ohm if I=0.5A V ripple would be 50mV

2. From voltage noise tool giving to the IC pin a sinusoidal stimulus IMAX=0.5A freq.=20Mhz the max ripple measured on the IC area is alway considerably smaller =28 mV.

 

Many thanks

Oscar

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