(I tried sending this yesterday but, because of a slight difference in my return email address, it seems to have been quietly dropped by the server)
The advice regarding the ceramic bypass capacitors is good as far as it goes, but, if your problem is a power supply which compensates slowly for load changes, you might try some bulk capacitance across the 3.3V input to the board as well (a large electrolytic). This should partly take up the initial changes in current so that the power supply has the time to respond and prevent serious falls and rises in the output voltage. If it is slow response in the supply, you should see the voltage spikes at its output not just near the FPGA. If adding bulk capacitance does not work, you may have to consider using a better power supply to provide the 3.3V On Sat, 2005-09-17 at 15:39 -0800, Uwe Zimmermann wrote: > ...plenty of fast capacitors (ceramic, not electrolytic) close to the > supply pins of the chips, short and wide power lines... > > Uwe. > > > > hi, > > here is a weered problem i stuck with developing a board of mine. > > it's a very heavy loaded board with many FPGA's on that "eat" a lot of > > power (100W) > > the problem is that those FPGA's do a heavy work once every 2msec wich > > creates power drop of about 0.2 volt. > > it results with the voltage looking like this: > > /\ ___/\ ___ > > \/ \/ > > > where the mean voltage is 3.3V > > > anyone know how to deal with thease voltage dropout (thy cause > > malfunctioning of the curcit) > > > regars, Michael > > -- Bob Mitchell PO Box 68 Phone (+61 2) 9449 4736 (21 Hudson Close) Fax (+61 2) 9449 1976 Turramurra, 2074 Mobile 0411554117 NSW, Australia Email [EMAIL PROTECTED] -- Author: Robert Mitchell INET: [EMAIL PROTECTED] Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
