Hi, We are planning on tying the shell to logic return on an upcoming video product based on the same logic (pun intended) also. We are prepared to separate them if it is a problem. We will be using separate power for analog and digital, but will be using only one reference for return currents. We will be very cautious in stackup, placement, routing, decoupling, etc.
Some of the better PC cards I have seen lately (wrt EMC) use only one return for signal currents but do separate that return from the D-shell, so we are fully prepared to do that if need be. They are using high bandwidth DACs with no output filtering so the designs are aggressive and well implemented. Good luck. [email protected] ---------- From: Robert Terry To: emc-pstc Subject: PCI Video Card List-Post: [email protected] Date: Thursday, August 29, 1996 10:23AM We are currently in the process of designing a new PCI bus video card. This card has 1 video D-Sub port. We have seen application notes indicating that the best way to minimize potential radiated emissions from this port would be to tie the D-Sub connector shell (chassis) to the logic ground on the circuit board. Thus minimizing the ground return impedance. However, our experience has indicated that we perform better (EN55022) when this D-Sub Shell (chassis) and the logic ground on the PCI card are separated. I am interested in what you folks think about this particular problem. Any responses would be appreciated. Thanks in advance for you replies! Please contact me if you have any questions or comments! Thank you! Robert L. Terry [email protected] 313-994-0591 Ext.235 Fax: 313-994-8408
