Some of the microchip dsPIC's have high speed PWM. Specifically the ones for digital power. The timing step resolution is 1.04nS. (Yes, that's almost a 1GHZ clock rate). I'm sure they do it with a ring oscillator locked to a lower frequency source, but the resolution is there, even at high speeds. It works well for the couple of hundred Khz to 1Mhz PWM frequency range, and even up to 10Mhz PWM. You could easily get into tens of Khz's and still be able to dither for higher resolution in software... dsPIC33FJ06GS101A for example: http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en537159 Dan On 1/8/2014 8:56 AM, volt-nuts-request@febo.com wrote: > Jan, > > with standard PWM generated from a microcontroller the repetition rates of > the signal may get VERY slow with higher resolutions, making it difficult to > make a pure DC signal from. You should consider to use a Sigma-Delta DAC > which is very easy to program in a microcontroller. I have used AVR Megas > with software Sigma Delta DACs and precision analogue multiplexers to switch > between the reference and GND up to 20 bits of resolution. Worked fine! > > Best regards > Ulrich