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Can a relatively low resolution DAC (say 12-bits) be used as a precision voltage reference with stability much better than the \$V_{max} \times 2^{-12}\$. If a certain DAC is set to a particular digital code for all time, is there a specification that gives me the noise voltage of this source?

For example the AD5681 has 16.5μVpp output noise listed for all models from 12 to 16 bits. For 5V full scale on the 12bit ADC the LSB is 1.2mV. Does this guarantee that I can set any voltage I like in 1.2mV step but that the output will be stable within 16.5μVpp? Assume a high-impedance load.

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  • \$\begingroup\$ It seems so, but make sure to look out for a noise-vs-frequency graph. There may be significantly more low-frequency noise than high-frequency noise and they might be quoting the latter figure \$\endgroup\$ – user253751 Dec 22 '17 at 5:03
  • \$\begingroup\$ Yes, the part I referenced has 16.5μVp-p from 0.1 Hz to 10 Hz but 250nV/√Hz up at 10kHz. Its hard to tell what the stability is like below 0.1Hz but even the 0.1Hz limit is just 0.014LSB. \$\endgroup\$ – Mike Dec 22 '17 at 5:36
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This will be thermal noise, random in nature. 6 sigma (aka 6 RMS) will be 1/500,000 vaguely remembered from Motorola Baldridge Award publicity.

Is 2PPM (1/500,000) a low enough occurrence for you?

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