I've heard it said both ways. But what is the deal? Well since decoupling caps are intended to minimize switching noise, which shows up at the pwr pin, what we're trying to do is dump the noise to gnd. This means minimizing noise on traces, so vcc trace(s) should be as short as possible. I've seen the Moto book too and it confuses the hell out of a lot of people. Does the Moto fact book say why the caps should be closer to gnd?? Theoretically the multi layer construction would seem to mean that since there are no traces, (a surface mount cap does require a trace/via, however short, to feed to the plane) the caps are filtering noise all across the board. Does this make sense? Pete Waddell ______________________________ Reply Separator _________________________________ Subject: Re: Placement of bypass caps Author: [log in to unmask] at Internet Date: 4/5/96 4:18 AM Mr Brooks The old rule of tumb was to set by-passes next to VCC so you did not have a pwr trace running on top of your board the length of your IC. How ever today most boards have planes for pwr, gnd So a even matrics of bypasses across the board will do the trick. All you are doing is decoupling vcc,gnd, if done correctly the board and parts will not make noise. Hope this helps DM PAVONE Micros ______________________________ Reply Separator _________________________________ Subject: Placement of bypass caps Author: [log in to unmask] at SMTPLINK-Micros Date: 4/4/96 5:45 PM I have several sources (including the Motorola FACT book) that say bypass caps should be placed as close as possible to the GROUND pin of the IC (not the power pin.) But I have seen few really specific discussions of why this is so. Some of my customers insist on having them placed as close as possible to the power pin. Can anyone give me a definitive explanation of where they should be placed, and why? Thanks Doug Brooks