[PEDA] minimum SMD to plane constraint ?
hello, i'm working with smt for the first time, and the board has 576MHz piped onboard thru a coax, so some signal integrity issues arise. i've established a stack that will give me a controlled impedance, and after laying a few critical lines by hand, i want to allow autorouting to complete the board. to avoid added inductances, i want the vias within 10 or 30mil of the pads, but when i autoroute, its placing them almost 100mil away from the pads. my problem is that i would like to set a design rule to allow a MAXIMUM distance from the pad to a power/ground via, but the smd-to-plane constraint is a minimum length. is there a rule (or other method) i can use to constrain the maximum trace length to a plane via during autoroute? thank you, miker p.s. to mr. lomax. the suggestion about using the edit/move/ component and then clicking an empty space to get a parts listing was a lifesaver. as you could tell, i had been doing a find and then having to travel back to where i wanted to drag it. thank you. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 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 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] minimum SMD to plane constraint ?
At 05:18 PM 3/6/2002 -0500, Robison Michael R CNIN wrote: my problem is that i would like to set a design rule to allow a MAXIMUM distance from the pad to a power/ground via, but the smd-to-plane constraint is a minimum length. is there a rule (or other method) i can use to constrain the maximum trace length to a plane via during autoroute? I very much doubt that the autorouter is that sophisticated. If the pins in question are power pins or are otherwise critical such that you must keep the lengths short, then you cannot trust the autorouter to handle them. I'd consider all power pins to be critical; I'd consider routing the entire power net by hand. I would routinely make the trace lengths *very* short; we'd put the vias in the pads if we could. Remember that it is the enclosed area in the entire power loop that matters. (The loop may be considered to be a complete circuit including the IC and the bypass cap and/or plane capacitance). p.s. to mr. lomax. the suggestion about using the edit/move/ component and then clicking an empty space to get a parts listing was a lifesaver. as you could tell, i had been doing a find and then having to travel back to where i wanted to drag it. thank you. Been there and done that, for far too long. Now, I don't use the parts listing much, I just enter the refdes for the part I need. Abdulrahman Lomax Easthampton, Massachusetts USA * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 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 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
