I need to generate signals to dim incandescent lights to one of 16 dimming levels.
I have built a 14-bit counter, which gives 16 discrete signals when used with always-on and always-off signals. To properly dim my lights, I need an 840Hz signal (that's the 60Hz mains frequency times 14 clock cycles needed) to drive my 14-bit counter circuit.
(Yes, I plan on using the same solution to generate 700Hz (50Hz * 14) for other regions of the world.)
Oh yeah, and I'd like this clock synchronized to the zero-crossing of the mains voltage, to minimize line noise when switching loads on.
I'm looking at Appnote XAPP462 and I don't think it's going to be possible to generate this singal on-chip. My desired output frequency is lower than the DCM will go. I know I can divide the output of whatever frequency I can generate, but I don't know if (or how) I can sync with the mains zero crossing at such low frequencies.
However, I'm an amateur here and wanted to toss it out to the more experienced crowd. Can this be done?