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?
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.