Hi, the board is 18 layer board. all the powering is done using the folowing scheme: 1. all major power consumers have a sepparate "iland" under it (in one of the layers) connected to the main supply (ie 3.3 / 1.5V) with a Ferrite Bead, and a large capasitor (typicly 47uF tantalum) on both sides of te bead. in addition there are decoupling capacitors (0.1uf/ 22pf) on each power terminal of the FPGA. All of the parts run from 120MHz clock distributed from CY2309. replacing the clock splitter with an industrial device, reduced the amounty of errors i get from the FPGAs. the power consuption is as folowing: showing the power line and consumption (where H stand for High and L for Low) /\ __/\ __ \/ \/ LHHHHHLHHHHH
the rise of the graph is on LOW power consuption (i think it got some thing to do with the responce time of the Power Supply i.e.: it feels high current, but take time to stabilize the voltage level, so we see power drop. then the current fall and we see a power rise) Pieter Hoeben wrote: >>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 >> > >Hi Michael, is the horizontal line the 3.3V? In that case >I do not only see a power drop, but also a power voltage rise? >That means that something may be reflecting, too much >inductance etc. Is it a multilayer with two power planes? > >You must use several capacitors, spread all over the board. >But do NOT place them neatly as you used to learn at school. >All those neat distances of th same length lead to a lot of >circuits with the same resonance frequency. If this is what >you have, user smaller and/or larger capaitors on several places. > >Regards, > >Pieter Hoeben > > >>anyone know how to deal with thease voltage dropout (thy cause >>malfunctioning of the curcit) >>Author: Michael Gefen >> INET: [EMAIL PROTECTED] >> >______________________________________________ > > Hoeben Electronics Phone: +31 6 51590081 > Ronkert 44 Fax: +31 13 5096025 > 5094 EW Lage Mierde Private: +31 13 5096200 > The Netherlands E-mail: [EMAIL PROTECTED] > http://www.hoeben.com >______________________________________________ > > > -- Author: Michael Gefen 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).
