At 04:10 PM 8/1/2002 -0400, yves Dubois wrote: >Hi All, > >I am routing a 4-layer board with only through hole components. > >I need to connected the supply pins of my IC's to the supply plane but I >would like to go through a decoupling cap first. > >Is there an easy way for have those pins not connected to the plane?
Yes, but it's a bad idea. This one comes up from time to time, it may have originated in old TTL 2-layer design practice, and I can recall thinking that this might be a good thing to do. However, if you make the inner planes close to each other, with, say, 5 mils of prepreg between them, the interplane capacitance will be high with minimal inductance. The decoupling caps then provide support at lower frequencies. By connecting the caps to the plane and isolating the power pins from the plane, which is what I think you want to do, you enlarge the power loop. You do not gain anything but trouble. However, you can isolate pads from the plane by setting a Manufacturing/Power Plane Connection Style design rule of "no connect" with a scope that covers the pads in question. If necessary, you could set a rule for each individual pad, but it should be possible to use a component class scope, i.e., create a class with the components which you want to not be directly connected to the plane, and then use that class for the design rule. ************************************************************************ * Tracking #: 21CC67D09BC73742A0A6A78B493B98683FFF59B4 * ************************************************************************ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
