On 13/9/21 6:31 pm, Julien Goodwin wrote: > https://www.microchip.com/en-us/product/PL500-16 (there's various other > versions depending on the frequency you're after) > > Haven't seen any discussion about this on-list, but the PL500 is an > easily (well, in normal times) available VCXO control chip, for those > who might want to make their own disciplined oscillator, especially at > less standard frequencies. I had some arrive today and put the board > I've designed as an OCXO, and was able to trim +/- ~3kHz (around 26MHz > nominal in my case, pretty much the expected +/- 150ppm), all really easily. > > I can't yet say much about quality as it turned out I'd put the wrong > regulator footprint on the board, and with no local regulation the power > rail was jumping all over the place, once I actually fix that and > hopefully get it mounted in its intended enclosure for thermal control > it'll be interesting how it goes (yes this was the project I was hoping > to use my SR620 to monitor the other week).
The thermal and shielding situation is to improve, but I did at least get local regulation fixed, and while improved, it's still not great. With a 1mH inductor on the input (pre-regulator) and the local regulator installed: https://twitter.com/LapTop006/status/1439081534053515266 Traces are: Yellow - Output signal (50-ohm terminated) Green - Control voltage Blue - 3.3v rail (main internal rail) Red - 5v input rail At a rough guess I either need more bulk capacitance on the 3.3v rail, or, more likely, lower impedance decoupling caps (I'm currently using 100n 0603 of the "whatever I have in stock" variety). Would welcome suggestions. I /do/ have an impedance analyzer that can handle this frequency (goes to 500MHz), but I lack the SMD text fixture for it. I suspect an output buffer would really help too, and on its own might significantly improve things. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
