On 27 Sep 01 at 12:52, GOPALCHETI,MANOJ (HP-Cupertin wrote: [....] > 1. With Power and Ground plane closer and far from signal layers > Signal Layer 1.5Oz, 8 mil trace > Dielectric 26mils > Plane Layer 1.00oz > Dielectric 8mils > Plane Layer 1.00oz > Dielectric 26mils > Signal Layer 1.5Oz, 8 mil trace with FR4 er=4.2 about 110 Ohm > 2. With Power and Ground plane separated far but closer to signal layers. > Signal Layer 1.5Oz, 8 mil trace > Dielectric 20mils > Plane Layer 1.00oz > Dielectric 16mils > Plane Layer 1.00oz > Dielectric 20mils > Signal Layer 1.5Oz, 8 mil trace about 100 Ohm. Nevertheless, I'd prefer Stackup 1. Better broadband decoupling of VCC/GND. Perhaps consider decreasing inner dielectricum down to 4 mit. That's much better. If necessary, fatten these traces where the impedance value ist important (mostly the stuff which goes out to the bus). Regards Matthias Mansfeld ----------------------------------------------- Matthias Mansfeld Elektronik * Printed Circuit Board Design and Assembly Am Langhoelzl 11, D-85540 Haar, GERMANY Phone: +49-89-4620 0937, Fax: +49-89-4620 0938 E-Mail: m.mansfeld@xxxxxxxxxxxxxxxxxxxxxx Internet: http://www.mansfeld-elektronik.de ------------------------------------------------------------------ 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