Andreas wrote:
But for the 100uVpp I have to ask for the measurement conditions.
Is the source (reference) connected via (long cable) and supplied
with another mains line
No
or on the same pcb with the same power supply (or battery supplied).
Yes. (And I have extensive design experience with ultra-low noise
power supplies, decoupling, RFI prevention, and low-noise grounding.)
Was the pcb cleaned before measurement to keep leakage low?
Yes, it was freshly built and cleaned upon completion (vapor-phase),
although that really has no bearing on commutation noise (charge
injection) internal to the switched capacitor circuit, which is where
all of the cyclical noise is generated. Can it be filtered
out? Perhaps, but not easily without raising some other noise or
drift problem.
How much noise did the reference generate? 1uV output measurement is
quite low with
typical 0.6ppm/V of a buried zener multiplied by 2 and a amplifier
with 1.6uVpp (referred to input).
I was using the ADR4520 (1uVp-p noise in the 0.1-10Hz band), with
post-filtering. When I said "about 1uVpp" output noise, I was
thinking order of magnitude for purposes of comparison to 100uV, not
precise value (which was more like 2-3uVpp).
Best regards,
Charles
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