Intrinsic Noise and Temperature Coefficients of Selected Voltage References

We require voltage references with a relative output voltage noise of at most 10
^-6
/radicHz in the frequency range of 0.1 mHz-1 Hz. We have investigated the output voltage noise and the external noise sources of a selection of references. Two external noise sources, i.e., supply voltage and temperature, and their coupling to the output voltage of the references were studied. The effect of supply voltage noise was negligible, whereas temperature noise had to be suppressed by stabilization. We found that samples of AD587LN- and MAX6126AASA50-type references fulfilled the requirements if the ambient temperature was stabilized to a level of approximately 50 mK/radicHz.