Istvan, thank you very much for your explanation. The socalled attached inductance seems to be the inductance I need for simulations. Should I use this attached inductance as the "intrinsic inductance" of the Specctraquest model? > For both of the above reasons, the loop inductance MINUS the plane inductance is the proper value for simulations. I call it attached inductance. > With agressive mounting of a two-terminal capacitor, the loop inductance can be much below the partial self inductance of the capacitor body. As it was also pointed out earlier, what you really need to use in simulation is not the loop inductance associated with the capacitor, because it contains the contribution from the plane inductance, and it would be double counted. Q: I assumed that the loopinductance consisted of the total inductance of the whole loop, including the capacitor. Is my assumption wrong then? Is the definition of loop inductance equal to total inductance excluding the capacitor? Q: then, how to specify ESL for ceramic capacitors, both standard 2-terminal and 3-terminal ones? My idea: ESL = equivalent series inductance and should reflect the partial inductance of the device. From your answer I understand, but correct me when I'm wrong, that when we measure the ESL of a capacitor we actually measure the "loop inductance associated with the capacitor", thus including plane inductance. When measured in a de-embedded fixture, don't we measure the capacitor's partial inductance then? And finally: isn't this partial inductance more or less the same as my definition of intrinsic inductance, solely the inductance of the capacitor body? Bart Bouma http://www.yageo.com Bart, > - I only can assume that what you wrote is correct. I'm not a si-engineer, > but a rf-guy and consequently think rf-wise. > Does this mean that the impedance associated with all the vertical > connections between the planes and the X2Y is dominant? > How to deal then with those multiple terminal devices? Do they have an > advantage by the fact that they have multiple parallel vertical > connections? > What about using multiple vias for X2Y or e.g. reversed geometry devices > as an 0306 MLCC. Will this help to provide a low impedance to the planes? As Nick pointed out, the vertical connection may not be dominant, but it is an inseparable part of the picture. Because the presence of a PCB plane under the capacitor will create a strong coupling between the bottom side of the cap and the plane, the loop inductance becomes smaller, and even though the vertical via inductance (the partial self inductance of via) may approach zero, this diminishing via inductance will come together with a reduction of loop inductance. With agressive mounting of a two-terminal capacitor, the loop inductance can be much below the partial self inductance of the capacitor body. As it was also pointed out earlier, what you really need to use in simulation is not the loop inductance associated with the capacitor, because it contains the contribution from the plane inductance, and it would be double counted. More importantly, you will find that for the same piece of capacitor, with the same exact pad and via geometry, the loop inductance is a function of the capacitor's location on the plane, because the plane inductance is location dependent. For both of the above reasons, the loop inductance MINUS the plane inductance is the proper value for simulations. I call it attached inductance. The attached inductance is much less dependent (ideally it is independent) of the capacitors location on the plane. The attached inductance value does depend on the construction of the capacitor body, but even more importantly it depends on the connection to the planes. With a two-terminal capacitor, the attached inductance can easily vary in a one-to-ten range, depending on pad and via geometry and on the location of the closest plane with respect to the capacitor. Best regards, Istvan Novak SUN Microsystems ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu