Zik, Never assume anything - especially wrt EMI. But it would be a good starting point. If you have access to a communications receiver and/or a good scanner you may be able to get a very rough idea of the amount of EMI produced at different frequencies. RP On 05/09/06, Zik Saleeba wrote: > Can I assume that if I use the layout shown in the data sheet that > I'll be relatively safe from EMI? In terms of changing to a lower > frequency switcher I'd really prefer to use a fast switcher in this > case to keep size and weight down. Every gram counts in this > application. > > Thanks, > Zik > > On 9/5/06, David VanHorn wrote: > > In my experience, the simple switchers are pretty noisy. > > They are designed to be easy. > > > > dVdT control is a big thing, a switch that turns on very fast can have > > oscillations due to inductance in it's emitter/source lead. Turning off > > quickly causes overshoot and ringing on that side, and just fundamentally > > speaking, a fast edge has lots of harmonics. Slowing down the turn on and > > turn off costs heat in the switch, and efficiency, but it lowers the amount > > of harmonics generated, and lowers/eliminates any oscillation or ringing. > > > > I disagree with the need for multilayer boards, I rarely use them. I am > > very careful about pcb layout, always returning current to it's source. A > > sloppily routed multilayer board is always quieter than a sloppily routed > > two layer board, and I suppose the extra layers are always helpful, but when > > I'm achieving noise levels that cause the part 15 test engineer to ask me if > > I'm sure that the device is on, I think that adding extra shielding is just > > adding extra cost. > > -- > > http://www.piclist.com PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist