Re: si5351a #synth
Dave New, N8SBE
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Had a crystal oscillator issue a few years ago that cause a lot of head scratching. We had been producing said module for several years with no problems, when suddenly we had a rash of dead modules (no oscillation) after they had been outside overnight in desert air that veered toward freezing, but not below.
We found ultimately that the oscillator was failing to start under low temperature conditions, but our modules are meant to operate over -40C to 85C and had been tested to that repeatedly over the current production runs.
Long story short (too late), we found that the original design had been marginal, in that the recommendation of the microprocessor manufacturer didn't line up with the recommendations of the crystal supplier. Production variation had exposed the margin, and thus, we started seeing failures at low temperature. So, after a lot of back and forth, we lowered the value of the ballast resistor in the tank circuit to increase the feedback, and voila! all the issues went away.
Several more years (and a few million) modules later, we have never seen another oscillator failure in the field.
Lesson: Every component has a data sheet, and often, they DON'T agree with those components' datasheets they need to interface to. Sometimes it takes a whole engineering team (and their OEM customer breathing down their back) to bash heads (and those of the component suppliers) until an optimal solution is found.
-- Dave, N8SBE