Thanks for the tips, Abdul. I particularly like the idea of the power and ground planes forming the plates of a capacitor.... that never occurred to me.
Bob Stephens A stackup that I particularly like, if I want to keep layer count down to 6, is one with the power and ground layers in the middle, fairly close together. Then, on either side of them, symmetrically, are signal trace layers, X and Y as described. And above those signal layers are the top and bottom layers. To match impedance with the buried layers, traces on the top and bottom need to be relatively fat, because they are well above the reference planes. There are a number of advantages to this stackup: the power and ground planes are close together (it might be 5 mils of prepreg or core between them). This creates a relatively high interplane capacitance which not only does yeoman work bypassing power -- perhaps even more effectively than scattered bypass caps -- but it also allows return currents to switch planes easily, through the interplane capacitance. Because the power and ground plane are so intimately connected at high frequency, they can act like a single plane for return purposes. The outside of the board serves to mount the parts and can be used for power traces or other low-speed signals, or, with the right trace widths, a few high-speed signals. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 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/[EMAIL PROTECTED] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
