Philip BraggPondering what to do with a nice chunky 2.048MHz crystal from a broken HP 3764A, I decided to make it generate 1216kHz for further Inovonics experiments. Their old gear often used this frequency as a master clock. #electronics
I'm using the normal 4000 series CMOS here, instead of the 74HC4000 series that I've been using recently. The 4000 series has some interesting quirks and varies enormously between manufacturers. You can't do the diode programming trick on Harris and TI 4024s at even a sedate 1MHz and the NS part I've used here still needed 56pF loading on the reset pin to work reliably. 74HC parts will do this at >30MHz, a huge difference in performance.
The circuit divides 2.048MHz 4011BE crystal oscillator down to 64kHz in a 4020 and this is sent to a phase-frequency detector in a 4046BE which divides its own VCO by 19 in the 4024 before comparing it with the 64kHz reference. There's a loop filter to stop the whole thing shaking itself off the spectrum and that's about it. Yes, two of the 4011 gates aren't connected to anything yet. Bad me!
ftg@synx508
There's just something about this style of construction that I find aesthetically pleasing.
In addition to the large groundplanes.
I should do more of it myself as well.
There's just something about this style of construction that I find aesthetically pleasing.
In addition to the large groundplanes.
I should do more of it myself as well.
@ftg This one was supposed to be prettier but I ran into the 4024 reset issue and things got a bit messy. Also the loop filter is uglier than I intended because I decided, perhaps wrongly, that the capacitors should ground to Vss rather than the ground plane..If I'd had a 2ยต2 >25V bipolar it would've been nicer.