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I'm attempting to design a data logger and the AD7193 seems to fit my requirements. I'd like to drive it by an external clock in a GPS-disciplined loop while sampling at an integer rate, as this would simplify comparing signals from distributed sensors. I am looking at choosing a SiT5358 oscillator which eliminates the need for a DAC as there's a digitally-controlled version. I'm new to designing hardware systems and have (at least) two questions about this pairing:

  1. The sample rate of the AD7193 is proportional to the f_CLK/A where A is a constant depending on many configuration options. Supposing A is fixed, then a desired sample rate could be achieved by varying f_CLK. Are there limits to how far from the internal 4.92Mhz clock rate we can vary f_CLK and still have stable operation?

The datasheet states, "[The] internal clock has a tolerance of +-4%." This seems to imply that operation would be unaffected by a deviation up to +-4%. Is a greater deviation advised with an external clock?

  1. The SiT5358 comes in LVCMOS and clipped sine wave output flavors. The AD7193 datasheet suggests either is tolerated by the AD7193, though they are attached slightly differently. Are there reasons to choose one over the other?
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  • \$\begingroup\$ Of course after posting, I find the external clock range of 2.4576-5.12 MHz in the datasheet for the AD7193. Still interested in #2! \$\endgroup\$
    – dls
    Aug 6 '20 at 16:12
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I'm interested in where you found the statement that a sine wave clock input is tolerated. What I found is:

Alternatively, the MCLK2 pin can be driven with a CMOS-compatible clock and with the MCLK1 pin remaining unconnected.

I'd follow this recommendation and choose the LVCMOS version of the oscillator. In general, I'd use (LV)CMOS oscillators as digital clock sources, except maybe if lowest phase noise is required.

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  • \$\begingroup\$ Thanks, I received some LVCMOS sample oscillators yesterday. As for sine being tolerated, I think I filled in some blanks. The datasheet says that crystal oscillators can be used, and I assumed that crystal oscillators have sinusoidal waveforms. \$\endgroup\$
    – dls
    Aug 18 '20 at 18:51
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    \$\begingroup\$ Probably just "crystal", without "oscillator". Many microchips include an internal oscillator circuit that needs an external crystal (without oscillator) to be connected to two pins. But often this circuit can be disabled and instead a digital clock is input into one of the two crystal pins from an external oscillator. \$\endgroup\$ Aug 19 '20 at 11:48
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    \$\begingroup\$ Ok, it does say that! Thanks for clearing up that concept. \$\endgroup\$
    – dls
    Aug 20 '20 at 2:22

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