FWIW, you can snub the switch node to dampen parasitic ringing in exchange of a loss in efficiency of a couple percent. I'm pretty sure I have seen this outlined in a few app notes.
On Mon, Dec 5, 2016 at 1:22 PM, jimlux <[email protected]> wrote: > On 12/5/16 9:13 AM, Dan Kemppainen wrote: > >> >> >>> Depending on the application, another possible application is to >>> sync up the DC/DC converter to the "main" clock source. This makes >>> the switching noise then coherent to the system, which either makes >>> it average out completely, or possible to filter it out in the digital >>> domain using a deep notch-filter in receiver applications. >>> >>> >>> >> You are assuming the switching noise is directly caused by the >> fundamental switching frequency, this may not always be the case. Often >> the fast edges can excite parasitic reactances in the board and >> components, which in turn oscillate and radiate at their own frequency. >> This is not necessarily related to the switching frequency. >> >> >> > > On big science spacecraft this is pretty common (which have all sorts of > sensitive science instruments, some of which may not have the best EMI/EMC > characteristics from both a source and susceptability standpoint). On the > other hand, as switching rates have gone up, it's not clear that > distributing a 20kHz "PWM reference clock" around is a good idea. > > On a radio I was recently working with, it used to radiate quite nicely at > about 15-19 MHz, even though the switching rate was in the hundreds of kHz > range - we figured that this is where the "antenna efficiency" (better with > higher freq) of the traces matched with the "harmonic power" (lower with > higher freq) > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
