Lee Ritchey's latest, "Right the First Time: A Practical Handbook on High Speed PCB and System Design" is available FREE at this link: http://www.thehighspeeddesignbook.com/ surfin' the learnin' curve, jack . On Thu, Apr 22, 2010 at 2:04 PM, Brooks, Bill <[log in to unmask]> wrote: > Toby, > > > > Point well taken. A very good presentation was done on the affects of short > rise time in slowly clocked digital boards. I believe Rick Hartley did that > one for us here in San Diego a number of years ago. > > He pointed out that the IC manufacturers were using something called ‘die > shrink’ as a technique to get more chips on a silicon wafer… which had the > result of increasing the rise time of the digital signal’s transition from a > zero to a one… this equivalent frequency of the transition was like in the > GHz and the boards that were used to functioning with much slower equivalent > circuits were now failing because of GHz signals being affected by the trace > length being much too long or un terminated with pull up or pull down > resistors to avoid ringing of the signal… Old boards that worked for years > for the military were now failing with the ‘same’ exact parts because they > really were not the same. They had changed internally… > > He gave us some pointers on design techniques to keep traces under 6 inches > long and to make sure the return currents had a path directly under the > signal thru a ground plane that was as close as possible to the signal… no > impedance matching was talked about at that time…Adding terminating > resistors or making sure the IC’s had them built in was talked about… and > the EMI/EMC suppression techniques were discussed as well I believe… > > > > Rick Hartley gave a very good workshop. Lee Richey of the Speeding Edge > also is a good source for information on this subject and I believe Doug > Brooks at UltraCad has some articles along those lines as well. > > > > Best regards, > > *Bill Brooks* | *Datron World Communications, Inc.** > *PCB Designer/Engineer | Office: 760-602-7004| Fax: 760-597-3777 | > [log in to unmask] > 1808 Aston Avenue, Suite 230, Carlsbad, CA 92008 | www.dtwc.com > > *Performance You Require. Value You ExpectTM* > ------------------------------ > ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------------------------------------- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ---------------------------------------------------------------------------------