If you wanted to be nutty you wouldn't go PWM at all, just like fractional-N sythns don't just mash 2 divider values. You would sigma-delta modulate your power stage. I don't know if you can buy one COTS, but there are plenty of papers on rolling your own.
On Sun, Dec 4, 2016 at 4:09 PM, Attila Kinali <att...@kinali.ch> wrote: > On Sun, 4 Dec 2016 15:45:55 -0500 > Bob Camp <kb...@n1k.org> wrote: > > > Given that the parts to build one are fairly easy to get and that we > likely have “nutty” > > EMI requirements. Maybe a small board that drops into a 78xx footprint > is the > > better solution. > > I don't fully agree. To go full "nutty" you would want to use the chips > in the QFN packages, as those have shorter leads and a large ground pad > to keep EMI down. But soldering an 0.5mm QFN by hand is impossible > (believe me, I tried) and not everyone has an oven. Also a lot of the > EMI performance depend on what output current you expect. Using a 1A > design for 10mA is a good way to get poor EMI performance as the > chip will go from PWM (aka fixed frequency) to PFM (aka fixed on time) > mode under low load to increase efficiency. The same goes for input > voltage. So we would need to do multiple designs for different > output current and input voltage ranges... which kind of defeats > the purpose of "a small board that drops into....". > > What could be done, though, is a small board with all components, > but the inductor on it. So then one could select the right inductor > for the application and solder it on. Using an inductor that is easy > to solder (like e.g. WE-PD3) with a wide selection of values should > do the trick. > > Attila Kinali > > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neil Stephenson > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.