If FLL: something that links frequencies, PLL: something that links phases, frequency detector: output proportional to frequency error, phase detector: output proportional to phase error (XOR), and the original question (about FLL) was how to implement a simple FLL, can an FLL be made by a phase detector? Can a PLL be made by a frequency detector? Phase_detector_XOR + RC + VCO-> FLL: equal frequencies, phase linked to VCO odds, in this case the frequency error is 0.
On Fri, Aug 28, 2015 at 7:14 PM, Charles Steinmetz <[email protected]> wrote: > Azelio wrote: > >> OK: the XOR gate with an RC is a defective PLL and a defective FLL. It >> is a simple way to have an idea of what an xLL should be but of no >> serious use. > > > No, not at all. I was suggesting that the XOR PLL you were commenting on > had problems. > > First, an XOR with or without an RC is not an FLL at all, of any sort. > Second, the XOR gate is a time-honored phase detector for PLLs, and if its > limitations are understood and accounted for, it makes a perfectly > serviceable PD for a PLL. There are other phase detectors that are more > popular these days, for a variety of reasons, but the XOR works just fine in > a proper design. > > See, e.g.: > Best, Phase-Locked Loops (2007), pp. 16-18 > Gardner, Phaselock Techniques (3rd ed) (2005), pp. 245-46 > Wolaver, Phase-Locked Loop Circuit Design (1991) pp. 55-59 > <https://en.wikipedia.org/wiki/Phase_detector> > <https://jaunty-electronics.com/blog/2012/09/exclusive-or-xor-gate-based-phase-detector/> > <http://memo.cgu.edu.tw/jtkuo/files/eelab%202014(iii)/1230_lab12_expxx_phaselockedloop.pdf> > and many, many, many others. > > > Best regards, > > Charles > > > _______________________________________________ > 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. _______________________________________________ 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.
