Paul, Yes, I switched from Lars's PWM based DAC to the MCP4725, which is available on an inexpensive breakout board. I wanted to avoid the original design's sensitivity to the 5V supply voltage. My OCXO has a 4V reference output and I use that to power the DAC. I use a resistor network between the DAC and the VFC pin of the OCXO to shift the DC level and reduce the control range, effectively increasing the 12 bit resolution of the DAC. A change I am contemplating is to switch to an AD5680 18 bit DAC which looks ideal for this application, but I have been put off by the tiny SOT23 package.
A schematic is attached. Recent changes, not reflected in this schematic, are a circuit to linearize the diode-R-C integrator and also output buffers for the 10 MHz and 1 pps. On Fri, Apr 5, 2019 at 12:10 PM paul swed <paulsw...@gmail.com> wrote: > Jim > The whole gpsdo seems impressive and also seems to be performing well. > When I look at the Lars GPSDO what you have built doesn't quite seem to > match. Such as using a real DAC. Is this one of the variants that can > exist? > Regards > Paul > WB8TSL > > > -- --Jim Harman
Arduino GPSDO Schematic v4.pdf
Description: Adobe PDF document
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