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And while we are at it: Does someone know how the AC frequencies are generated?
More specific, reason why I ask: While performing AC calibration on DAQ cards we usually perform a sine fit and look at the residuals. At certain frequencies one can clearly see phase jumps in the residuals. So the 5700 has some sort of accumulated phase error register, that results in added or skipped DAC values.. . In order to avoid that: Does somebody know how one could pick output frequencies that avoid these jumps?
Maybe something like : the 5700 has an internal clock frequency f_clk , use a M/N factor (both integer) add the internal x and/or divide by another y and you get the 'clean' frequencies ? .. 
Form the manual the internal oscillator is not using DDS to generate the AC signal, but classical old style phase shift RC oscillator with an PLL (actually more than one) for frequency control. So if everything is ok, there should be no sudden phase shifts. So no easy list of good and bad frequencies. It is more like a few frequencies (or ranges) that seem to show glitches on that special unit. The could be a general design weakness or tolerances on that special unit. I would consider 3 possible sources for this:
1) The PLL adjustment range somehow reaches limits as the internal control reaches limits. This might be fixable with some internal automatic readjustment of the frequency control. (coarse osc. settings).
2) Very small glitches might occur if the coarse setting is to good in some cases and the phase comparator is in a kind of dead zone. This should be really weak disturbances - don't know if one would see them on the scope.
3) The loop filters need to be adjusted with the frequency. There could be borderline cases where the loop filters are not really good, maybe too much direct feed through. So there could be frequency ranges that are not that good.
One could do a test with external reference frequency instead of the internal one, to check if the glitches come from the ref. frequency synthesizer or the main oscillator / PLL.
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