On Sun, 4 Dec 2016 16:22:02 -0500 Scott Stobbe <scott.j.sto...@gmail.com> wrote:
> 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. I guess you are refering to spread-spectrum techniques. Such DC/DC converters exist, but are usually those with high power ratings. IMHO it is also not worth the effort, as its main use is to meet EMI emission requirements. The only application that comes to my mind where spread-spectrum actually helps are high sensitiv radio receivers where every spur is a nuisance. For most other use, and time-nuts use in particular, it is much less useful. The noise energy is not gone. It is still there, just spread over a large bandwidth. In time measurement applications, noise is integrated over time _and_ frequency. Thus even if the noise is spread over a large bandwidth, the energy will still contribute to the uncertainty and degrade the ADEV. It will be just harder to identify as the peak is now much smaller and wanders in frequency. It is much better to the design such, that as little as possible of the switching energy leaks out of the DC/DC converter and filter out the rest. 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. Attila Kinali -- Malek's Law: Any simple idea will be worded in the most complicated way. _______________________________________________ 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.