On 09/30/2018 05:57 AM, Tom Van Baak wrote: > What's a clever, simple, reliable (pick 2 of 3) way to get 16 MHz out of 10 > MHz? Low phase noise isn't a big requirement and jitter doesn't need to be > sub-nanosecond. The main requirement is perfect cycle count accuracy. This is > for driving a 16 MHz microcontroller from a 10 MHz Rb/Cs/GPSDO. 10 MHz input > is likely sine; 16 MHz output is 3v3 or 5v CMOS. > > Thanks, > /tvb
When I have needed this, it has been for microcontrollers. I have let the microcontroller do the locking, with 10MHz applied directly to an input pin: I run a reasonably fast* interrupt. Once inside the interrupt, I read the current timer value, and read the port 8 times into registers. This gives me 8 samples spaced 45 degrees apart on the 10MHz input, which are then converted to a 8-bit field. That 8-bit value is then used in a lookup table, which outputs a phase value. This is compensated by what was read from the timer (how late we got into the interrupt). The phase error is then accumulated, and drives a PWM DAC, connected to a varactor on the crystal. It adds 3 external components in total, and for an annoying case like 8/5, it may well wobble 90 degrees. It started with this Christmas-vacation experiment I never really finished: https://n1.taur.dk/permanent/synth_v2.pdf /Kasper Pedersen *) oscillator_frequency * max_xtal_deviation * 4, typically 16kHz or so. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
