Hi As always, the real answer it “that depends”.
If your objective is wide band phase noise and you want to start from 100 MHz and get 10 MHz (fig 6 in the Lamda paper), you can get at least another 6 db with a simple divide by 10 chip than with all the fancy stuff. Bob > On Jun 3, 2015, at 12:17 AM, Bruce Griffiths <[email protected]> > wrote: > > You can always cleanup the outputs of the CPLD or FPGA by resynchronising the > outputs to the input clock using a dedicated D flipflop for each output. > > Bruce > > > > On Wednesday, 3 June 2015 3:22 PM, Bob Camp <[email protected]> wrote: > > > Hi > > A lot depends on exactly which CPLD or which FPGA you are looking at and how > they put the guts of it together. If you find one that is “just right” it > *might* be within > 10 db of high speed CMOS. Since there is a 20 db delta between the HC you > mention > and the AC that leaves a bit of room. > > If you have a part with a bias generator in it, just forget about using it. > You will have all > sorts of strange spurs that come and go. They will be broadband. They will > take the > noise floor up into the 100 dbc / Hz range in some cases. > > If you are trying to use the internal PLL, it’s phase noise isn’t going to be > great. Numbers > like -135 dbc / Hz at 100 KHz offset are not uncommon on an HF output. > > As straight dividers, they might get to -16x dbc/ Hz region. That compares to > the -174 dbc / Hz > you could expect under similar conditions with something like AC or faster > CMOS. You > are more likely to get there on a fast CLPD than on an FPGA. Either way you > can run > into bum parts. > > Bob > >> On Jun 2, 2015, at 9:13 AM, David C. Partridge >> <[email protected]> wrote: >> >> Is this a sensible thing to consider doing? Or would I be better sticking >> to AC/HC/AHC/LVC logic? >> >> Regards, >> David Partridge >> >> _______________________________________________ >> 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. > > > > _______________________________________________ > 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.
